NEW MATERIAL:The CSF having the following physical and chemical properties. Molecular weight, 19,000±1,000 by sodium dodecylsulfate-polyacrylamide gel electrophoresis; isoelectric point, PI=5.5±0.1, 5.8±0.1 or 6.1±0.1; ultraviolet absorption, absorption peak at 280nm and minimum absorption at 250nm; amino acid sequence, 21 amino acids from N-terminal are shown in the formula.

USE: Remedy and clinical examination reagent for hypoleukocytosis, etc.

PREPARATION: The objective CSF can be produced e.g. by culturing a cell strain capable of producing human marrow cell differentiation and proliferation promoting factor (CSF) in a serum-free culture liquid, subjecting the supernatant liquid of culture product to gel-filtration, adsorbing the obtained fraction to reverse-phase high-performance liquid chromatography carrier and purifying the eluted fraction by high-performance molecular sieve chromatography and isoelectric electrophoresis, etc.