The present invention 1s directed to a method of assay of rheumatoid arthritis (RA). More particularly, the present Invention is directed to the assay of human immunoglobulin A- α- _| -antitrypsin complex (IgA-α* _| AT) In patients who are suspected of having or are being treated for RA. Descriptlon of the prior art

Rheumatoid arthritis has been described as an unresolved systemic inflammation 1n which immune dysfunction and genetic susceptibility play roles. In earlier stages, It 1s often characterised by fluctuating remissions and exacerbations, and 1n later stages by a chronic granulatamous response (pannus formation) leading to tissue destruction notably of bone and cartilage. The synovial membrane 1n RA has many of the characteristics of a hyperactive 1mmunolog1cally stimulated lymphold organ and the ratio of T suppressor to T helper lymphocytes has been shown to be significantly reduced.

Since there 1s no unambiguous test distinguishing RA from other acute or chronic Inflammatory diseases, differentiating RA from other arthritides, such as systemic lupus erythematosus ⁽ SLE ⁾ , ankyloslng spondylitis (AS), polyartlcular gout (PAG), or psorlatic arthritis ⁽ PsA) 1s often difficult. Diagnosis of RA is usually made according to American Rheumatism ^" Association (ARA) criteria, i.e.:

(1) morning stiffness;

(2) joint tenderness or pain on motion;

⁽ 3) soft-tissue swelling of the joint;

⁽ 4 ⁾ soft-tissue swelling of a second joint (within three months);

⁽ 5 ⁾ soft-tissue swelling of symmetrical joints (excludes distal interphalangeal joint);

(6) Subcutaneous nodules;

(7) X-ray changes; (8) Serum positive for rheumatoid factors;

wherein diagnosis of 3 or 4 of these factors is considered representative of probable RA and diagnosis of 5 or more of the factors is considered representative of definite RA.

The most widely used immunodiagnostic assay of RA, the so-called Waaler-Rose assay, is based upon an antibody (rheumatoid factor) to the Fc region of IgG. Rheumatoid factor (RF) is present 1n about 60% to 70% of those individuals afflicted with RA. The test 1s not satisfactory because 1t has been found to give unacceptably large numbers of false positives or negatives, and it does not assess the response to therapy or predict activation or reactivation of the disease process. Moreover, based as it is on a haemagglutination or latex agglutination end point, 1t 1s difficult to standardize from one clinical laboratory to another. More seriously, It can provide a positive result on only about 70% of chronic sufferers from this disease and, In any case, the immunopathogenlc role of RF has never been established.

Recently, evidence has begun to point to the covalently linked (S-S) complex between IgA and α- _| -antitrypsin (α _j AT) as a major Immunopathological factor 1n RA. This complex 1s found at grossly elevated levels 1n the sera of patients with IgA myelomatosis but has also been detected in abnormally high amounts in the circulation of RA patients. The following evidence suggests that the measurement of circulating levels of IgA-α- _j AT complex would provide a more relevant Immunodiagnostic indicator of rheumatoid arthritis than those currently used:

(1) It is present in abnormally high levels in the circulation and joint fluids of virtually all patients with untreated chronic rheumatoid arthritis. (The currently utilized rheumatoid factor is detectable in the sera of only about 70% of such patients) .

(2) The serum level of IgA-α- _j AT complex appears to fall in those patients who show a beneficial clinical response to treatment with second line anti-rheumatic drugs. ⁽ 3) It is also detectable at abnormally high levels in those

AS patients who show erosive joint changes.

(4) Unlike other so-called disease markers which are measured in RA, such as rheumatoid factor and acute phase proteins (e.g., haptoglobin and C-reactive protein), both in vitro and in vivo studies have provided a plausible explanation of the 1mmunopathogen1c1ty of the IgA-α _j AT complex. Thus, not only can the formation of the IgA-α- _j AT complex lead to the consumption of as much as one-third of the total available α- _j AT

(one of the major anti-proteases) 1n rheumatoid patients' serum or joint fluids, but the IgA-α _j AT complex Itself 1s capable of eliciting release of degradative proteolytlc enzymes from isolated macrophages (by a cytolytic process dependent on the activation of the alternative complement pathway). Furthermore,

Injection of the Isolated complex Into normal rabbits' knee joints results In the rapid development of an acute arthritis, which shows the gross anatomical and histopathological features of the clinical condition. (See, Stanworth, D.R., "IgA dysfunction 1n rheumatoid arthritis", Immunology Today, New

Directions in Research, £. pp. 43-45 (1985); Stanworth D.R. "The role of IgA In the Immunopathogenesls of rheumatoid arthritis"

Chapter 7 in "Imrnunogenic Mechanisms of Arthritis" Eds.

J. Goodacre and D.W. Carson, pp 122-142 (19B7) and Dawes, P.T.,

Jackson R., Shadforth, M.F., Lewin, I.V., and Stanworth, D.R.,

"The relationship between the complex of i munoglobulin A and a^-antitrypsin, Its constituent components and the acute phase response, as measured by C-react1ve protein in rheumatoid arthritis treated with gold or D-pen1cillamine", British Journal of Rheumatology, 2__. pp. 351-353 (1987)).

The current method of measuring IgA-α- _| AT complex relies on a two-dimensional immunoelectrophoresis comprising a first dimensional electrophoretic separation of complex from free α- _| AT in agarose, and its identification by second dimensional electrophoresls Into agarose-contalning antiserum directed specifically against α- _j AT. The amount of complex is then quantitated (in arbitrary units) by determining the area under

its precipitation peak (on the subsequently dried and stained plate) by planimetry. However, this is a laborious and time-consuming procedure.

Accordingly, it would be desirable to provide an easily performed assay for the IgA-α^AT complex. Initial attempts were made to use an ELISA in which either ant1-IgA or anti-α* _| AT antibody was first coated onto the wells of micro-titratlon plates followed by incubation with an IgA-α- _| AT complex-containing test specimen, reaction with either antl-α _j AT IgG or anti-IgA IgG antibody, respectively and final development with an enzyme labelled anti-IgG antibody. However, it is a problem that such a complex cannot be detected reliably by an assay which depends on the binding of the IgA-o^AT complex to an antibody to IgA or α* _| AT, since this approach would result in the binding of uncomplexed IgA or α- _j AT which are also present 1n unquantified amounts in the sample from the patient, thus Interfering with the quantitative measurement of the IgA-α- _j AT complex.

It has been necessary, therefore, to produce an antibody directed specifically against human IgA-α- _j AT complex. An initial attempt to accomplish this by Immunising rabbits with purified IgA-α- _j AT complex failed, as the resultant antisera reacted also with uncomplexed IgA and o^AT. Summary of the invention

It has surprisingly been found that a monoclonal antibody can be produced which is virtually unreactive with free IgA and α- _j AT, but is specific to the naturally occurring IgA-α- _j AT complex. Moreover, when attempting to prepare such antibodies from the fusion of mouse spleen cells with myeloma cells, it was found that yields of spleen cells were very low, making the production of the hybridomas impossible. It was necessary to find a solution to this problem, which, as it transpired, was caused by toxicity of the human IgA-α- _j AT complex to the mouse macrophages. It was demonstrated that incubation of isolated peritoneal mouse macrophages with human IgA-α- _j AT complex leads to a substantial release of the cytoplasmic enzyme LDH and a subsequent

destruction of the macrophages. The problem was eventually overcome as described below.

Furthermore, an Immunogenic peptide has been synthesised comprising a first peptide fragment having an amino acid sequence or an analogue thereof found 1n the Fc region of human IgA and a second peptide fragment having an amino acid sequence or an analogue thereof found 1n human α- _j AT, said first and second fragments being covalently bound to one another, wherein an antibody raised against said peptide Is substantially non-react1ve with free human IgA, 1s substantially non-reactive with free human α- _j AT, and binds to the naturally-occurring complex of human IgA and α- _j AT (IgA-α- _j AT). Surprisingly, polyclonal antibodies raised against the said peptide were also found to be substantially non-reactive with free IgA and α- _j AT. Monoclonal antibodies of the same or better specificity will doubtless be raisable against it. Moreover, the recently developed chlmerlc antibodies (Relch an, L., Clark, M., Waldmann, H. and Winter G., Nature 332, pp 323-327, 1988)), single chain antibodies (PCT Patent Application Publication Number W0 88/01649 Genex Corporation) and single domain antibodies (Ward, E.S., Gϋssow, D., Griffiths, A.D., Jones, P.T. and Winter, G. Nature 341. pp 544-546, (19B9)) having elements anti to the said naturally occurring complex and peptide can be expected to be producible. Accordingly the Invention provides a Ugand comprising an antibody domain specific for an antigenie determinant of a complex of human IgA and α- _j -antitrypsin, said antibody domain being substantially non-reactive with free human IgA and free human c -antitrypsin. The invention also provides a method of assay of rheumatoid arthritis (RA) in an analyte suspected to contain a complex of human IgA and α _j -antitrypsin (IgA-α _j AT) as an indicator of RA, which comprises detecting or measuring immunologlcal binding between the said complex and the above said ligand.

This invention further provides an assay kit for carrying out a method of assay of human RA in an analyte suspected to contain a complex of human IgA and α- _j -antitrypsin (IgA-α- _j AT) as an indicator of RA, the kit comprising an IgA-α _j AT complex and a ligand whose antibody domain 1s specific for an antigenie determinant of IgA-α _j AT, but substantially non-reactive with free human IgA and free human α- _j AT. Description or the preferred embodiments

The following definitions are used throughout the present specification:

"Assay" means a method of detection or measurement.

"IgA-α* _| AT complex" means the complex as found in human patients serum, unless otherwise stated or the context otherwise requires. Fab' fragment represents one "arm" of the two "arms" of the "Y" shaped antibody configuration; the fragment retains antigen-binding ability.

F(ab')2 fragment represents two Fab' "arms" linked by disulphide bonds; the fragment retains antigen-binding ability. Fc fragment represents the single "tall" or central axis of the "Y" shaped antibody.

The ligands of the invention comprise an antibody domain specific for an antigenie determinant of a complex of human IgA and human α- _j AT (IgA-α- _j AT). The said antibody domain is relatively non-reactive with free human IgA and free α- _j AT. The complex of IgA and α- _j AT (IgA-α- _j AT) is the naturally occurring complex found in analytes taken from patients suffering from rheumatoid arthritis. Most preferably, but as exemplified below, not necessarily, the ligand comprises a monoclonal antibody raised against such a complex. The most preferred monoclonal antibodies are obtainable from hybridomas which are the subject of patent deposits described herein below. Polyclonal antibodies raised against the purified, naturally occurring, complex were not found to be specific for the IgA-α- _j AT complex, the resulting antisera reacting also with uncomplexed IgA and α- _| AT.

Alternatively the ligand can be an antibody raised against a synthetic peptide of the invention. This synthetic peptide is a covalently linked conjugate of short chain peptides representative of those parts of the IgA heavy chain and α- _j AT chain sequences which comprise an IgA-α- _j AT complex-specific immunogenlc determinant. In a particular embodiment, the present invention provides and utilizes a first peptide fragment having an amino add sequence found 1n the Fc region of human IgA or an analogue of said sequence, and a second peptide fragment having an amino acid sequence found in human α- _j AT or an analogue of said sequence, which are covalently bound to one another. The preferred form of covalent bonding is an S-S linkage which preserves the immunogenlc three dimensional conformation of the linkage of the penultimate cysteine residue, relative to the C-terminal end of human IgA, in the Fc region of human IgA to human α- _j AT. The structure of the preferred IgA-α _j AT complex has not yet been completely elucidated. However, It is Hkely that the covalent S-S bridging occurs between the only cysteine residue (No. 232) of human α- _j AT and the cysteine residue (No. 495) occupying the penultimate cysteine position in the α-chain of human IgA, to which J-cha1n 1s known to conjugate in the formation of polymeric IgA.

The first peptide fragment preferably corresponds to an amino add sequence of the Fc region of human IgA containing the penultimate cysteine residue, relative to the C-terminal end of human IgA, comprising 5 to 20 amino acid residues, preferably 10 to 15 amino acid residues, or analogues thereof. The first peptide fragment preferably contains at least the amino acid sequence Val-Met-Ala-Glu-Val-Asp-Gly-Thr-Cys-Tyr which corresponds to residues 487-496 of the human IgA α-chain, or an analogue thereof. This is the minimum sequence length which will lead to the formation of a stable conjugate. Most preferably the amino acid sequence comprises Val-Ser-Val-Val-Met-Ala-Glu-Val-Asp-Gly-Thr-Cys-Tyr

which corresponds to residues 484-496 of the human IgA α-chain or an analogue thereof.

The second peptide fragment preferably corresponds to an amino acid sequence of human α- _| AT, including the cysteine residue which bonds covalently to the IgA α-chain, comprising 5 to 20 amino acid residues, preferably 10 to 15 amino add residues, or analogues thereof. The second peptide fragment preferably comprises at least the amino add sequence Hls-Cys-Lys-Lys which corresponds to residues 231-234 of human α- _j -AT, or an analogue thereof. This Is considered to be the minimum sequence length which will lead to the formation of a stable conjugate.

Most preferably the amino add sequence comprises

Gly-Met-Phe-Asn-Ile-Gln-Hls-Cys-Lys-Lys-Leu-Ser-Ser which corresponds to the residues 225-237 of the human α- _| -AT or an analogue thereof.

Accordingly, a particularly preferred Immunogenlc peptide of this invention comprises at least the following amino add sequence:

or an analogue thereof.

Most preferably, the Immunogenlc peptide comprises the peptide conjugate of the following amino acid sequence:

Val-Ser-Val-Val-Met-Al -Glu-Val-Asp-Gl -Thr-Cys-Tyr Gly-Met-Phe-Asn-Ile-Gln-His-Cy Is-Lys-Lys-Leu-Ser-Ser or an analogue thereof (hereinafter designated peptide F017-F018). Antibodies to the IgA-α^AT complex (whether the natural complex or synthetic peptide) may be readily prepared by techniques well-known in the art. Thus, polyclonal antibodies can be obtained from immunised rabbits by exsanguination. Monoclonal antibodies can be prepared by the Kohler-Milstein method in mice provided that spleen cells are always used in excess in the fusion and that cytolysis of the resultant hybridomas is co batted as necessary by addition of fresh spleen cells. The hybridomas have then to be screened for specificity

to the complex. Fab' and F(ab')2 fragments of such monoclonal or polyclonal antibodies may be prepared in well-known ways. Any of these molecules providing antibody domains to the complex can be used. For diagnostic purposes, the antibody will react with the naturally occurring IgA-α- _j AT complex from the individual under test to produce a detectable product. An antibody composition used in any test designed to quantitate the presence of IgA-α- _| AT must contain sufficient antibody to react with all of the naturally occurring IgA-α _j AT complex. Such dlagnostlcally effective amounts o-f antibody will vary appreciably with a number of factors well known to those skilled 1n the art. These include, for example, the sensitivity and specificity of the test employed, the instrumentation available and the amount of analyte under test. The most preferred analyte 1s a serum sample since this gives a better Indication of RA than joint fluids.

Detection and measurement of levels of the IgA-α _j AT complex, preferably 1n serum or joint fluid, may also be used as a prognostic indicator of RA In order to facilitate the better management of patients with "early" (pre-eros1on stage) RA, where diagnosis is normally difficult.

While enzyme-1Inked Immunosorbent assay (ELISA) is preferred in this invention, other assays, e.g. radio-immunoassay, precipitation, agglutination, direct and Indirect immunofluorescence and complement fixation can be used. These assays may employ any protocol such as competitive, inhibition or sandwich type.

The assays generally require a detectable label. The anti-IgA-α- _| AT antibody, an anti-antibody (e.g. goat anti-rabbit serum), an anti-IgA antibody or an anti-α- _j AT antibody may be labelled. Useful labels include fluorescent labels such as fluorescein, rhodamine or auramine and radioisotopes such as ^C, 131J _J 125j _an( j 35$ -τ _ne preferred enzyme labels include horseradish peroxidase, β-D-glucosidase, β-D-galactosidase, urease, glucose oxidase plus peroxidase, and acid phosphatase.

Currently available procedures for detecting the aforementioned labels are well-known and include colorimetric, luminometric and fluorometric techniques, as well as various instrumental methods of detecting radio isotopes. The assays will normally be carried out so that the detectable product becomes bound to a support, so as to ensure ready separation from the unbound serum sample.

Usable supports Include glass or plastic surfaces, especially the inner surface of test tubes or a surface of a test plate. Typical examples of flat surfaces useful in the enzyme-linked immunoassay procedure (ELISA) or the radloimmunoassay procedure

(RIA) include glass, nitrocellulose paper or plastics such as polystyrene, polycarbonate or various polyvinyls. Particles which can be used for macroscopic procedures wherein the reaction product can be detected visually, e.g. the hemagglutination procedure, include biological particles such as sheep red blood cells or human group 0 red blood cells, and biologically Inert particles such as charcoal, bentonlte or latex beads. Such beads can be formed of polystyrene, polyvinylpyrrol1done or various polyvinyls.

Attachment to the support surface may be by direct adsorption, forced adsorption or chemical coupling 1n accordance with known procedures.

Preferred binding schemes are as follows (* = labelled substance):

Sandwich Assays support/anti-IgA-αιAT/IgA-α- _| AT analyte/anti-IgA*; support/anti-IgA-α- _j AT/IgA-αiAT analyte/anti-α^AT*; support/anti-IgA-a- _j AT/IgA-aiAT analyte/anti-IgA-a- _| AT* (the 2nd antibody having a different specificity from the first)

Inhibition Assays

Support/IgA-α- _j AT/anti IgA-α^AT* + analyte (pre-incubated before addition to support/IgA-α- _j AT)

Competition Assays

Support/anti-IgA-α- _j AT

\ IgA-α^AT analyte.

A wide variety of kits are possible for carrying out assays of the present Invention. They comprise a ligand of the Invention and an IgA-α- _j AT complex. Preferably the assay kit will provide a means of assaying the complex either by (A) a sandwich assay wherein the kit provides In addition to the above, a second detection ligand which comprises an antibody domain capable of detecting an IgA-α- _j AT complex when bound to the first Ugand, or (B) a competitive or Inhibition assay 1n which the said IgA-α _j AT complex component of the assay kit 1s an Immunogenlc analogue, and 1s more preferably an Immunogenlc synthetic peptide, of the naturally occurring complex. The Ugands are preferably polyclonal or monoclonal antibodies as set forth above and Fab' or F(ab')2 fragments thereof or single domain or single chain antibodies as will be apparent to one skilled in the art. The detection ligand 1n a sandwich assay need not be an antibody which has specificity to the whole complex. Any such ligand which provides a means of attaching label to the analyte IgA-α- _j AT (without interfering with the binding of the analyte to the capture antibody) 1s usable. Thus 1t could conveniently be an antibody raised against IgA or α- _j AT.

The detection Ugand 1n the sandwich assay, the antibody which competes with the analyte 1n a competition assay and the antibody which is pre-reacted with the analyte 1n an Inhibition assay have to be labelled at some stage. While these reagents can be provided as ready labelled conjugates it is normally more convenient merely to label them by providing a further antibody thereto which is labelled as a separate component. Typically the second antibody 1s an immunoglobulin and the further antibody provides ant1-1mmunoglobul1n by being raised 1n a different host animal .

Normally, all components of the kit will be provided in separate containers.

Appropriate washing, enzyme substrate and buffer solutions would be provided with the assay kit, together with a detailed Instruction sheet, Including advice on the calculation and Interpretation of the results.

Although the synthetic peptide or purified naturally occurring IgA-α- _j AT complex (being covalently linked) is relatively stable, 1t could become dissociated 1f test samples were mishandled (e.g. exposed to reducing conditions).

It is important to keep analytes such as specimens of sera and joint fluids at 4°C over the short term, awaiting assay. If, however, they cannot be tested within a day or two they should be stored in the frozen state (at or preferably below -20 ^β C), after having had cellular and non-cellular debris removed from them by gentle centrifugation.

The following Examples Illustrate the Invention. "Tween" is a Registered Trade Mark. Example 1 Formation of mixed disulphide between peptldes F017 and F018

Both peptldes F017 and F018 were synthesized using the 9-fluorenylmethoxycarbonyl (Fmoc) solid phase peptide synthesis chemistry in an LKB Blolynx 4170 peptide synthesizer. The cysteine (Cys) residues in both peptldes F017 and F018 had side-chain protection of S-triphenyl ethyl (TRT).

15 mMol Iodine in acetic add: water (8:2) was added to a mixture of 5 mMol F018 and 5 mMol F017 in acetic acid-water (8:2). The mixture was gently mixed on addition and then left at 4°C for 16 hours. Peptides F017-FOL8 were also treated in a similar way separately to act as controls. Each peptide preparation was then run on a Necleosil 5 C18 reverse-phase HPLC column with a methanol gradient (A = 5% ethanol in water, B = 95% methanol in water ⁾ . The HPLC traces were compared and the fractions comprising the extra peak obtained from the F017 and F018 mixture

were collected and used as F017-F018 peptide complex.

In a similar manner, the peptides Val-Met-Ala-Glu-Val-Asp-Gly-Thr-Cys-Tyr and His-Cys-Lys-Lys can be prepared. Likewise, the peptide conjugate

Val-Met-Al a-Gl u-Val-Asp-Gly-Thr-Cys-Tyr

I Hi s-Cys-Lys-Lys can also be prepared 1n the same manner.

Example 2

Production of rabbit anti IqA-αiAT

New Zealand White rabbits were injected subcutaneously with 200 μg of purified human IgA-α- _j AT complex or 200 μg of peptide conjugate (F017-F018) emulsified in complete Freund's adjuvant, followed by further injections of the same amount of complex or peptide conjugate emulsified with incomplete Freund's adjuvant at 14 to 28 days. About a month later the animals were bled. Example 3

Isolation of IgG from rabbit antiserum and the preparation of various cleavage fragments

One volume of saturated (NH ) ₂ Sθ4 solution pH 6.5 was added to one volume of rabbit serum (to give a final salt concentration of 50% saturated), drop wise with stirring at 4°C.

After being left to stand for 6 hours, the precipitate was separated by centrifugation (3000g for 30 minutes) and the supernatant was discarded. The precipitate was redissolved in 0.3 volumes of 0.01M phosphate buffer pH 8.0 and dialysed against 3 changes of the same buffer. This final dialysed solution (e.g. 5ml) was placed on a DEAE-Sephadex column (e.g. 12.0 x 1cm) which was pre-equilibrated with O.OIM phosphate buffer pH 8.0, and eluted with the same buffer. 2.0ml fractions were collected. The fractions corresponding to the protein (i.e. IgG) peak were pooled and concentrated by ultrafiltration. Further IgG containing fractions were retrieved from the column by application of a salt gradient (i.e. 0.01M - 0.10M P0 ), using 3 column volumes of each buffer in a gradient maker.

The composition of all fractions was recovered and checked by immunoelectrophoresis against anti-whole human serum; and those fractions containing only IgG were pooled, concentrated by ultrafiltration and stored below -20°C. Preparation of proteolvtic cleavage fragments (a) Preparation of Fab' and Fc fragments

Native IgG is hydrolysed in the hinge region by papaln to yield two antigen-binding fragments, Fab' and one dimer of the C-terminal half of the heavy chain, Fc' (Porter 1959). These are all of similar size (50,000 molecular weight) but they can be separated by ion-exchange chrom tography. In general, proteolytic fragments of immunoglobulins can be separated under non-denaturing conditions because they are not held by non-covalent bonds. Procedure:

1. Dissolve 1 mg of papain in 100 μl of 0.1M sodium phosphate buffer and quickly add 50 μl of this to the IgG. Mix gently and incubate at 37°C overnight (16 hours).

2. Dlalyze against water and then 3 x 500 ml of 0.01M sodium acetate pH 5.5

3. Equilibrate the Ion exchanger with the 0.01M acetate buffer and pack into the column, wash with the same buffer at room temperature.

4. When both sample and exchanger are fully equilibrated, apply the sample to the column and elute with at least 60 ml of starting buffer until the absorbance at 280 nm has returned to baseline. Then apply a linear gradient, total volume 200 ml, from 0.01M to 1M acetate all at room temperature. Collect 5 ml fractions and monitor the absorbance at 280 nm. 5. Protein eluted with the starting buffer and the first peak in the gradient consists mostly of Fab'. The third peak is Fc. The protein yield in the three peaks should be about 90% of the original IgG.

(b) Preparation of F(ab')2. Fab' and pFc' fragments Native IgG is also hydrolysed by pepsin. However, this enzyme cleaves on the C-terminal side of at least one α-α-chain disulphide bond to give a divalent antigen-binding fragment, F(ab')2. It also degrades part of the Fc portion to small peptldes to leave a dimer of the C-terminal quarter of the α-chain, pFc'. The F(ab')2 fragment can be reduced to the onovalent Fab' fragment. Procedure: 1.Dissolve 2 mg of protein in 200 μl of the acetate buffer and add 100 μl of this to the IgG solution. Mix gently and incubate at 37°C overnight (16 hours).

2. Neutralize with 2M tris (approximately 300 μl - this Irreversibly inactivates the enzyme) and centrifuge at 2000 g for 10 minutes to remove any precipitate.

3. Apply the supernatant to the G-200 column and elute with TBS. Collect 2.5 ml fractions and monitor the absorbance at 280 nm.

4. The first major peak is F(ab')2. In front of this is undigested material and just behind 1t any Fab' or Intact Fc formed. These minor products are sometimes not completely resolved from F(ab')2 and form shoulders on the main peak. pFc' In the next peak and small peptldes are eluted in the total column volume Fab'. F(ab')2 can be directly reduced to Fab', if required, by the following procedure:

A. Pool the fractions containing F(ab')2 and concentrate to 5 ml (this should give a protein concentration of about 6 mg/ml). Add 0.5 ml of the IM tris buffer and 50 μl of EDTA solution. B. Add 50 μl of dithiothreitol solution (0.1M dithiothreitol in IM tris buffer, freshly prepared) and incubate in a sealed tube at room temperature for 1 hour with stirring.

C. Cool on ice, cover with foil and add 50 μl of iodoacetamide solution. Incubate in an ice bath for 30 minutes with stirring.

D. Add 5 μl of dithiothreitol solution, incubate at room temperature for 15 minutes and apply the mixture to the G-200 column. Elute as for the peptic digest. There will be a small peak of undissociated F(ab')2 in its original position followed by a major peak of Fab'. Example 4

Assessment of specificity of rabbit (polyclonal) anti-complex antisera

96-well flexible assay plates (Falcon 3912) were coated with antigen, by overnight incubation at 4°C with 120 μl aliquots of one of the following:

( i) IgA-α-,AT (5 μg/ml) ( ii) IgA (5 μg/ml) (iii) α- _j AT (5 μg/ml) made up 1n 0.05 M carbonate/bicarbonate buffer (pH 9.6).

The plates were then washed 3 times for 1 minute each with phosphate buffered saline (PBS), pH 7.2 containing 0.05% Tween 20 (PBS/Tween).

Normal (NRS) and test (anti-complex) rabbit sera (100 μl), as prepared in Example 2, were titrated in PBS/Tween (neat to 1 in 2 dilutions or neat to 1 in 5 dilutions) and added to the antigen coated plates. The plates were then Incubated for 1 hour at 37°C. (Negative Control: PBS/Tween used alone or blank plate, incubated with normal rabbit serum). The plates were washed after incubation as before.

100 μl aliquots of goat-anti-rabbit/IgG/horseradish- peroxidase were added at a dilution of 1/1000 PBS/Tween and the plates were then incubated for 1 hour at 37°C. After incubation, the plates were washed as before. 100 μl aliquots of substrate were added, the substrate comprising:

20 mg o-phenylenedi mine; 250 μl H ₂ 0 ₂ ; and

50 ml 0.15 M citrate phosphate buffer (pH 5). The colour was allowed to develop for 5-15 minutes and then

the enzymatic colour reaction was stopped by addition of 25 μl of 25% H ₂ S0 to all wells.

The optical density of the contents of each well was read at 492 nm (OD492) 1n a Tltertek automated plate reader. The results set forth 1n Table 1 indicate that the antisera had a considerable specificity for the complex, giving a high 0D492 at high antibody dilutions, some reaction towards α- _j AT and no significant difference over controls towards IgA.

Table 1 Assessment of specificity of polyclonal rabbit anti-IgA-α- _j AT complex antlserum by ELISA.

Mean zeroed values of optical density measured at 492 nm.

ANTIGEN COATING ON ELISA PLATE

OO

I

Example 5

Production of monoclonal antibodies

Immunisation

BALB/c mice were Injected intraperitoneally (i.p.) with 50μg IgA-αiAT complex emulsified 1n equal volumes of Freund's complete adjuvant. Injections were repeated on day 14 and 28 with IgA-α- _j AT complex emulsified in Freund's incomplete adjuvant. Test tail bleeds taken on day 28 or later were assayed for the presence of anti-peptide antibodies by indirect ELISA. Three days prior to fusion, mice showing raised serum antibody tltres received a further booster Injection (I.p.) of 50μg IgA-α- _j AT complex in PBS. Fusion

Hyperimmunized mice were sacrificed by cervical-dislocation, the spleen removed and cells isolated and washed. The spleen cells were fused with a mouse myeloma cell line (Ag. 8.653 or NSO or NS1) from a culture 1n logarithmic growth. By modification of the Kδhler and Milstein method (Kδhler, G. and Milstein, C,

Nature (London) 256., pp. 495 (1975)), spleen and myeloma cells were fused at a ratio of 2:1, respectively, using 40% PEG

(polyethylene glycol - mol. weight 1450). 1ml PEG was added dropwise over a 1 minute time period to the pellet of mixed cells

(spleen and myeloma) and diluted with serum-free medium. The fusion suspension was distributed into 96-well plates and cultured in medium containing HAT (Hypoxanthine, aminopterin and thymidine). The poor growth of hybridoma cells was rectified by the addition of normal mouse spleen cells (immediately after fusion), as a source of fresh macrophages to replace those cytolysed by the injected IgA-α^AT complex. After 10 days, plates were examined for growth of hybridomas. Supernatant removed from these cells was screened for the presence of anti-IgA-α _j AT complex antibodies by indirect

ELISA. The following binding scheme was employed (* = labelled substance): Support/IgA-αiAT/Anti-IgA-α^AT/goat anti-mouse IgG*

Cloninα

When positive wells were identified as producing the desired antibody, the hybrid cells were cloned by limiting dilution and clones assayed again. Hybridomas were cultured in flasks or grown in mice. Ascitic fluid was raised in BALB/c mice primed with pristane (0.5 ml injected i.p.) a few days prior to Injecting with 10 ⁵ hybrid cells. Tumour formation should result after some 2-4 weeks and accumulated ascitic fluid removed by sacrificing the mouse and removing the contents of the abdominal cavity with a pipette. The concentration of monoclonal antibody in ascitic fluid was determined at every tumour passage; this ranged from 5-15 mg/ml. Screening

The procedure employed in screening the monoclonal antibodies was as follows. Plates were prepared comprising the following layouts:-

(a) plate coated with human IgA-α^AT complex (by incubation with a solution containing 5μg protein/ml) + cell supernatant + goat anti-mouse-peroxidase labelled antibody; ⁽ b) plate coated with free human IgA (5μg/ml solution) + subsequent steps as above;

(c) plate coated with free human α- _j AT (5μg/ml solution) + subsequent steps as above.

Cells producing those supernatants which reacted positively only in system (a) above, were selected as hybridomas which were producing monoclonal antibody directed specifically against the

IgA-α^AT complex (whilst being unreactive with free IgA or free _αι AT).

Two such hybridoma cell lines, secreting monoclonal antibodies to the naturally occurring IgA-α AT complex, have been deposited at the European Collection of Animal Cell Cultures, PHLS Centre for Applied Microbiology and Research, Porton Down. Salisbury, Wiltshire SP4 0JG, England. The first, designated NLW.54, was deposited on 6th February 1990 under the accession number ECACC 90020611, under the provisions of the

Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure. The most preferred antibody, designated NLW.50, was deposited on 13th December 1990 under the accession number ECACC 90121302. Example 6

Measurement of IgA-α- _j AT complex bv 2-Dimens1ona1 Immunoelectrophoresis (2D-1EP)

A solution of 1% agarose (Sea kern HGT Agarose ICN B1omed1cal

Ltd.) 1n 0.05M barbitone buffer pH 8.6 was prepared. 4ml of this melted agarose solution was poured onto a 7.6 x 5.0cm glass plate and allowed to set, whereupon 1.1 x 5.0cm strips were cut and transferred onto clean 7.6 x 5.0cm glass plates (1 strip of agarose per plate). A 2mm diameter well was cut into the agarose, 15mm from the left edge and 7mm from the bottom of the plate. 3μl of the test serum was applied to the well and a small spot of bromophenol blue was added to the sample. The plates were placed onto the electrophoresis apparatus with the sample well nearest the cathode and the agarose strip running length-ways to the anode. Filter paper wicks were placed on the agarose, 1cm in from each end. The plates were then electrophoresed at 20mA/6 plates with cooling, until the slower moving (albumin bound) bromophenol blue marker spot reached the wick on the anode side of the apparatus (approximately 2 hours).

50μl of sheep anti-human α- _| AT was added to 4ml of melted agarose at 56°C and poured onto the glass plates into the space above the

1.1 x 7.6cm strip. The plates were then electrophoresed at 90° to the first electrophoresis at 20mA/6 plates overnight. The plates were removed from the electrophoresis apparatus and placed between weighted filter paper for 30 minutes. The plates were then transferred to an incubator until fully dried. The plates were stained with 0.05% Coomassie Brilliant Blue (Coomassie is a

Registered Trade Mark) for 10 minutes and then destained with methanol/acetic acid/water (40:4:56) until precipitin lines could clearly be seen. The area of the 'slower' moving peak (IgA-α- _j AT complex) was measured using a planimeter, and the complex

concentration quoted as area in cm ² .

The concentration of IgA-α- _j AT complex in a panel of test pathological specimens was measured by this method. The results are set forth in Table 2 below.

Table 2

RA - Rheumatoid Arthritis AS = Ankylosing Spondylitis * = Steroid treated patient

Example 7

Measurement of IgA-α- _j AT complex bv sandwich ELISA assays General method

A 96-well flexible assay plate (Falcon 3912) was coated with a first or capture antibody of optimal concentration made up in a

coating buffer (0.05M carbonate/bicarbonate buffer pH 9.6). 120μl aliquots of this antibody (e.g. 1/16000 dilution) were adsorbed onto the plate by incubation at 37 ^β C for 1 hour, room temperature for 1 hour or overnight at 4°C. The plate was then washed 3 times for 1 minute each time with phosphate buffered saline (pH 7.2) containing 0.05% Tween 20.

100 μl aliquots of IgA-α- _] AT complex or test serum samples (diluted 2 fold or 5 fold) were added to the plate and Incubated for 1 hour at 37 ^β C. The plates were then washed as before. 100 μl aliquots of a second antibody of optimal concentration (e.g. 1/6000 Rabbit-antl-IgA-α^AT complex) were added to the plate and then Incubated at 37°C for 1 hour. The plate was again washed as before. Then, 100 μl aliquots of a third antibody of optimal dilution were added. This antibody (e.g. Goat-anti- Rabbit IgG) was labelled with the enzyme horseradish peroxidase. The plates were Incubated at 37°C for 1 hour and then washed as before.

100 μl aliquots of the substrate for the enzyme horseradish peroxidase was added. The substrate comprised 20mg o-phenylenediamine, 250μl H ₂ 0 ₂ and 50ml 0.15M citrate-phosphate buffer, pH 5.0. The colour was allowed to develop for 5-15 minutes and then the enzymatic colour reaction was stopped by the addition of 25μl of 25% H ₂ S0 to all the wells. The optical density of the contents of each well was read at 492 nm (OD492) in a Titertek automated plate reader. Results:

1. Sandwich ELISAs incorporating polyclonal antibodies directed against IgA or α- _j AT. The capture antibody is ant1-IgA

The procedure for carrying out the sandwich ELISA was as described above. 4 assays were carried out employing 2 sheep and 2 rabbit polyclonal anti-IgA antibodies as the capture or first antibody. The binding schemes for these ELISA assays are shown below:- Assay 1: Support/Sh.(l)anti-IgA/IgA-α^AT complex/Sh.anti-α^AT + labelled anti-sheep antibody.

Assay 2: Support/Sh.(2)anti-IgA/IgA-α* _| AT complex/Sh.anti-α- _| AT + labelled anti-sheep antibody.

Assay 3: Support/Rb.(1)anti-IgA/IgA-α* _| AT complex/Sh.anti-α^AT + labelled anti-sheep antibody. Assay 4: Support/Rb.(2)ant1-IgA/IgA-α- _| AT complex/Sh.anti-α- _j AT + labelled anti-sheep antibody.

Sh. = Sheep

Rb. = Rabbit

The results of the above assays 1-4 are set forth 1n Table 3 below. The samples 1-12 are the same as those samples in Table 2 of Example 6, where the concentrations of IgA-α- _j AT complex were measured by 2D-IEP. Their rankings In the 2D-IEP are reproduced in Table 3 for ease of comparison.

Table 3

Sample No. Assay 1 Assay 2 Assay 3 Assay 4 Rank in 0D492 Rank 0D492 Rank OD492 Rank OD492 Rank 2D-IEP

As can be seen qualitatively by comparing the rankings and can be confirmed by statistical analysis, the ELISA failed to confirm the results of the 2D-IEP. For example, in assays 1 and

3, samples 6, 7 and 9 all gave low values despite their high 2D-IEP values, the concentration of complex in sample 10 appeared low by 2D-IEP but high by ELISA value.

In assays 2 and 4, samples 6, 7 and 9 all gave low ELISA values, despite their high 2D-IEP values. These results show that this approach cannot be used to measure IgA-α _j AT complex. The discrepancies in results obtained by the two methods (ELISA and 2D-IEP) are probably due to the free IgA binding preferentially to the anti-IgA antibody coating the ELISA plate, thereby preventing tne binding of IgA-α- _j AT complex.

2. Sandwich ELISA systems incorporating polyclonal antibodies directed against IgA or αjAT. The capture antibody is anti-α-jAT

A sandwich ELISA procedure was carried out as described above. The following binding scheme was used:- Support/Sh.anti-α- _j AT/IgA-αiAT complex/polyclonal anti IgA + labelled antibody

In this Example, different pathological specimens were measured and compared to measurements of the same samples by 2D-IEP. The results are shown in Table 4 below:-

Table 4

Patient's Name Diagnosis ELISA results* at serum diln. of: Complex

1/5 1/10 1/20 1/40 level ddeterm. bbyy 22 DDii en. I.E.

Weaver RA 0.98 0.94 0.85 0.77 4.05

Whyte " 1.03 0.91 0.72 0.52 2.80

Reid " 0.71 0.45 0.21 0.08 1.00 to cr*

Barton " 0.11 0.10 0.08 0.07 2.40

Wright " 0.22 0.12 0.09 0.06 0.45

Snape " 0.12 0.10 0.09 0.06 1.00

Albandol Myeloma 0.07 0.09 0.08 0.06 26.00

Jones " 0.13 0.12 0.09 0.07 12.00

+ - 0D (optical density) units * - arbitrary units

The wide differences in the results obtained by the two methods, as seen e.g. in the rankings, are probably attributable to the binding of free α^AT to the coating antibody preferentially, thereby inhibiting binding of the IgA-α _j AT complex.

3. ELISA sandwich assays employing antibody (monoclonal or polyclonal) to the naturally produced complex as capture or first antibodies

Carrying out a sandwich ELISA procedure as described, the following binding schemes were used:

1. Support/Mc.anti-IgA-α- _j AT/Iga-αiAT complex/Sh.Pc.anti-IgA + labelled anti-sheep antibody.

2. Support/Mc.anti-IgA-a- _j AT/Iga-a- _j AT complex/Sh.Pc.anti-a- _| AT + labelled anti-sheep antibody. 3. Support/Mcanti-IgA-α^AT/IgA-α- _j AT complex/Rb. anti IgA-α^T + labelled anti-rabbit antibody.

4. Support/Rb.Pc.anti-IgA-α _j AT/IgA-α _j AT complex/Sh.Pc. anti-IgA + labelled anti-sheep antibody.

5. Support/Rb-Pcanti-IgA-α- _j AT/IgA-α _j AT complex/Sh.Pc. antl-α- _j AT + labelled anti-sheep antibody.

6. Support/Rb.Pc.anti-IgA-a- _j AT/IgA-aiAT complex/Mc.antl-IgA- α* _| AT + labelled antibody.

Pc. = Polyclonal antibody raised against the purified complex,

IgA or α- _j AT as indicated in the above binding schemes. Mc. = Monoclonal antibody secreted by hybrldoma NLW54 in accordance with the invention.

Sh. = Sheep.

Rb. = Rabbit.

The results of a sandwich ELISA incorporating binding scheme ⁽ 3 ⁾ above are shown in Table 5 below. This table shows a comparison of OD492 values obtained from the ELISA with results from 2D-IEP.

- 28 -

Tabl e 5

As seen in Table 5 above, three of the four samples from binding scheme (3) giving high 2D-1EP values (>3.0 units) also show higher OD492 values. Although in serum samples containing lower levels of IgA-α^AT complex, there is little difference in the ELISA values measured, this result may be remediable by increasing the sensitivity of the assay.

The results from ELISA assays incorporating binding schemes 1 and 2 (data not shown) reveal a similar trend to that for scheme

(3 ⁾ . These results show that in a sandwich assay the detection antibody can be anti- to the whole complex or to either component thereof.

The results obtained from assays incorporating binding schemes 4, 5 and 6 reveal that it is not possible to measure the

IgA-α- _j AT complex by using plates coated with polyclonal rabbit anti-complex antibody (data not shown). Example 8

Measurement of IgA-α* _[ AT complex bv inhibition ELISA A 96-well rigid plate (Falcon 3040) was coated with 500μg ml ^~ l bovine serum albumin (BSA). Aliquots of 200μl were added to each well and the plate was incubated at 37 ^β C for 1 hour. The plate was washed three times for 1 minute each time with phosphate buffered saline (PBS) pH 7.2 containing 0.05% Tween 20 ⁽ PBS/Tween 20). 100μl aliquots of IgA-αiAT complex or test serum samples were titrated (2 fold or 5 fold dilutions 1n PBS/Tween 20) then lOOμl aliquots of monoclonal antibody to the IgA-α AT complex from the NLW54 cell line were added to an optimal concentration ⁽ e.g. 1/20000 to give a final concentration of 1/40000) and the plate was incubated overnight at 4°C.

After the overnight incubation described above, the plate was centrifuged at 3000 rpm for 15 minutes, and 90μl aliquots were transferred from each well onto another plate pre-coated with IgA-αiAT complex. This plate was precoated as follows. A 96-well flexible assay plate (Falcon 3912) was coated with lOOμl aliquots of IgA-α AT complex of 5μg ml-1 concentration, made up in coating buffer (0.05M carbonate/bicarbonate buffer pH 9.6). This plate was then incubated at 37°C for 1 hour, room temperature for 2 hours or 4°C overnight and then washed as described above. lOOμl aliquots of antibody labelled with the enzyme horseradish peroxidase, of optimal dilution (e.g. labelled goat anti-mouse IgG at 1/1000 dilution) were added and the plate was incubated at 37°C for 1 hour. The plate was washed as before. lOOμl aliquots of substrate solution were added. The substrate solution comprised 20 mg o-phenylenediamine, 250μl H ₂ 0 ₂ and 50 ml 0.15M citrate phosphate buffer, pH 5.0. The colour was allowed to develop for 5-15 minutes before the enzymatic reaction was terminated by adding 25μl of 25% H ₂ S0 ₄ to all the wells. The optical density of the contents of each well was read at

492nm (0D492) in a Titertek automated plate reader. The calculation of percentage inhibition was as follows:-

% inhibition = 1- 0D492 sample - 0D492 blank x 100

OD492 uninhibited sample - OD492 blank The results of this assay are shown 1n Table 6. The results were compared to measurement of the same sera by a conventional 2D-1EP procedure. The ELISA resυlts are expressed 1n terms of the reciprocal of the dilution of serum (the titre) required to be added to give 50% Inhibition of the labelled antibody.

Table 6

As will be seen from the rankings in Table 6, there was a good agreement between the ELISA and the 2D-IEP. This has been calculated statistically as about 69%. This percentage is even more impressive (89%) if the results for serum 32 (the sample giving the highest ELISA inhibition value) are ignored. Example 9

Measurement of IgA-α^T complex bv a double antibody capture ELISA

96-well flexible assay plates (Falcon 3912) were coated with capture antibody of optimal concentration made up in coating

buffer (0.05M carbonate/bicarbonate; pH 9.6).

Aliquots (120 μl) of antibody at 1/1000 dilution were absorbed onto a plate by incubation at 37°C for 1 hour, at room temperature for 2 hours or at 4°C overnight. The plate was then washed (3 x 1 minute) with phosphate-buffered saline (PBS), pH

7.2, containing 0.05% Tween 20.

To the above pre-coated plate, monoclonal antibody to

IgA-αiAT complex as secreted by hybridoma NLW54 1n accordance with the invention, was added and the assay carried out according to the protocol previously described in Example 7. The following binding scheme was employed:-

Support/Mc. rat anti-mouse IgG/Mc mouse ant1-IgA-αιAT complex/ IgA-αiAT complex/

Pc.Rb. anti-IgA.αiAT/labelled anti-rabbit antibody

Mc. = Monoclonal antibody Pc. = Polyclonal antibody Rb. = Rabbit The results of determining the level of Ig-αiAT complex in a panel of test sera (rheumatoid arthritis and normal controls) by the above double antibody capture method were compared with the levels of IgA-αiAT complex measured by 2D-1mmunoelectrophores1s, single antibody capture ELISA (as described In Example 7(3) following binding scheme 3) and inhibition ELISA techniques (as described in Example 8). These results are shown in Table 7.

Table 7

This sample (*) is anomalous in that it consistently shows high ELISA values and low 2D-IEP values. It is probably giving false low 2D-IEP readings. Example 10 Comparison of results from employing murine monoclonal NLW.50 and NLW.54 in ELISA system

A double antibody capture assay was also carried out in which the monoclonal antibody to IgA-αiAT complex was secreted by hybrldoma NLW.50 in accordance with the invention. In this assay, polystyrene plates were employed (Dynatech-Im ulon 4). The assay was carried out as described above in Example 9 except that the test serum was diluted 1/100. The use of a better monoclonal antibody coupled with the use of polystyrene plates contributed to the Increased sensitivity of this assay. The following binding scheme was employed: support/Rat Mc Anti-mouse IgG/Mc anti-IgA-αiAT/IgA-αiAT complex/ Rb Pc antl-IgA-αiAT/labelled goat anti-rabbit antibody. Mc = Monoclonal antibody Pc = Polyclonal antibody G = Goat Rb = Rabbit

The results are shown in Table 8 below.

Ta l

When the results are plotted as ELISA results for NLW.54 and

NLW.50 vs the 2D-IEP measurement, then the correlation coefficient are 0.56 and 0.72 respectively - confirming that

NLW.50 is slightly more sensitive than NLW.54 and the reason why it is thus the preferred antibody.

Example 11

Effect of having one or two detection antibodies in a double antibody capture ELISA assay

A double antibody capture ELISA assay was carried out as previously described in Example 9 except that polystyrene plates

(Dynatech-Immulon 4) were employed and the test sera was diluted

1/100. The effect of using one or two detection antibodies in the ELISA assay was investigated. The following binding schemes were employed: ⁽ 1 ⁾ support/Rat Mc anti-mouse IgG/Mouse Mc anti-IgA-αiAT/IgA-αiAT complex/Sh Pc anti-IgA/D anti Sheep labelled antibody.

(2) support/Rat Mc anti-mouse IgG/Mouse Mc anti-IgA-αiAT/IgA-αiAT complex/Sh Pc anti-IgA labelled.

Mc = Monoclonal antibody Pc = Polyclonal antibody

Sh = Sheep

D = Donkey

The monoclonal anti-IgA-αiAT antibody was that secreted by hybridoma NLW.50 in accordance with the invention. The results are shown in Table 9 below.

Tabl e 9

SERUM SERUM (arbitrary units) (arbitrary units) Binding Binding Binding Binding Scheme Scheme Scheme Scheme 1 2 1 2

The results of this assay show that there was no loss of sensitivity when employing one detection antibody Instead of two as 1s the tradition 1n ELISA assays. This has the advantage of reducing the time needed for carrying out the assay by one hour, and the cost of carrying out such an assay Is reduced also.

When comparing the results of the two assays by plotting the results gained for binding scheme 1 against binding scheme 2, the correlation coefficient was 0.88 and the standard deviation <0.001 which is highly significant. The point representing serum sample number 2 has been eliminated from this statistical analysis (if included the correlation coefficient is 0.97).

Example 12

Comparison of ELISA sandwich assay employing one detection antibody only with 2D-IEP measurements

A double antibody capture ELISA assay was carried out in accordance with the method described In Example 9. Polystyrene plates (Dynatech-Immulon 4) were employed and the test sera was diluted 1/100. The monoclonal capture antibody was that secreted by hybridoma NLW.50 in accordance with the invention. The following binding scheme was employed: support/Rat Mc anti-Mouse IgG/Mc anti-IgA-αiAT/IgA-αiAT complex/

Sh Pc anti-IgA/labelled D anti-sheep IgA antibody.

Mc = Monoclonal antibody

Pc = Polyclonal antibody

D = Donkey Sh = Sheep

Measurement of IgA-αiAT complex by 2D-IEP was carried out according to Example 6. The results are shown in Table 10 below.

Table 10

When these samples were plotted on a graph comparing 2D-IEP and ELISA, the correlation coefficient was 0.73, which is significant.

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(A) TELEPHONE:

(B) TELEFAX:

(2) INFORMATION FOR SEQ ID NO: 1: (i) SEQUENCE CHARACTERISTICS:

(A) LENGTH: 10 amino acids

(B) TYPE: polypeptide

(C) TOPOLOGY: linear (ii) MOLECULE TYPE:

(v) FRAGMENT TYPE: C terminal fragment (ix) FEATURE:

(D) OTHER INFORMATION: Residues 487-496 of human IgA chain (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 1: Val-Met-Ala-Glu-Val-Asp-Gly-Thr-Cys-Tyr 487 490 495

(3) INFORMATION FOR SEQ ID NO: 2: (1) SEQUENCE CHARACTERISTICS:

(A) LENGTH: 13 amino acids

(B) TYPE: polypeptide

(C) TOPOLOGY: linear (1i) MOLECULE TYPE:

(v) FRAGMENT TYPE: C terminal fragment (ix) FEATURE:

(D) OTHER INFORMATION: Residues 484-496 of human IgAα chain (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 2:

Val-Ser-Val-Val-Met-Ala-Glu-Val-Asp-Gly-Thr-C s-Tyr 484485 490 495

(4) INFORMATION FOR SEQ ID NO: 3: (1) SEQUENCE CHARACTERISTICS:

(A) LENGTH: 4 amino adds

(B) TYPE: polypeptide

(C) TOPOLOGY: linear (ii) MOLECULE TYPE:

(v) FRAGMENT TYPE: Internal (ix) FEATURE:

(D) OTHER INFORMATION: Residues 231-234 of human α AT (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 3: His-Cys-Lys-Lys

231 234

(4) INFORMATION FOR SEQ ID NO: 4: (i) SEQUENCE CHARACTERISTICS:

(A) LENGTH: 13 amino acids

(B) TYPE: polypeptide

(C) TOPOLOGY: linear (ii) MOLECULE TYPE:

(v) FRAGMENT TYPE: internal (ix) FEATURE:

(D) OTHER INFORMATION: Residues 225-237 of human α- _j -AT (x1) SEQUENCE DESCRIPTION: SEQ ID NO: 4: Gly-Met-Phe-Asn-Ile-Gln-His-Cys-Lys-Lys-Leu-Ser-Ser 225 230 235