Interleukin-10, also called cytokine synthesis inhibitory factor, is implicated in tumorigenesis, and it has been shown that polymorphisms in its gene promoter correlate with differential amounts of production. IL-10 is an important cytokine with anti-inflammatory, anti-immune, and antifibrotic functions. It is also an important regulatory cytokine whose involvement extends into diverse areas of the human immune system. IL-10 is a recently described natural endogenous immunosuppressive cytokine that has been identified in human, murine, and other organisms. IL-10 significantly affects chemokine biology, because human IL-10 inhibits chemokine production and is a specific chemotactic factor for CD8+ T cells. It suppresses the ability of CD4+ T cells, but not CD8+ T cells, to migrate in response to IL-8. Interleukin-10 gene polymorphisms and interleukin-10 production capability may contribute to the development of skin squamous cell carcinomas after renal transplantation. The interleukin-10 locus contributes to the heritability of psoriasis susceptibility. With regard to sudden infant death, IL-10 is of special interest. This is an immunoregulatory cytokine that plays an important role in the development of infectious disease. The mIL-10 gene is mapped to mouse chromosome 1 and the hIL-10 gene is also mapped to human chromosome 1. The standard product used in this kit is recombinant human IL-10, consisting of 160 amino acids with the molecular mass of 18.6kD.