The gene IL-3 encodes interleukin 3, a hematopoietic colony-stimulating factor (CSF) that is capable of supporting the proliferation of a broad range of hematopoietic cell types.1 Interleukin-3 (IL-3), a protein of 140 amino acids, is chemically synthesized by means of an automated peptide synthesizer and is shown to have the biological activities attributed to native IL-3.2 The cDNA sequence for murine interleukin-3, one of the colony stimulating factors that regulate haematopoiesis, codes for a polypeptide of 166 amino acids including a putative signal peptide.3 The mouse IL 3 gene is located on chromosome 11.4 The human gene encoding IL 3 is tandemly arrayed on the long arm of chromosome 5.5 The standard product used in this kit is recombinant human IL-3, consisting of 133 amino acids with the molecular mass of 15KDa.