Background
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Interleukin 10, also known as cytokine synthesis inhibitory factor (CSIF), is the charter member of the IL-10 cytokine family. This family currently comprises IL-10, IL-19, IL-20, IL-22, IL-24 and IL-26. All known IL-10 family members are secreted -helical proteins. IL-10 is a secreted, possibly glycosylated, polypeptide with a molecular weight of 18 kDa. Based on human studies, IL-10 is likely to circulate as a nondisulfide-linked homodimer. IL-10 is synthesized as a 181 amino acid (aa) precursor with a 19 aa signal sequence and a 162 aa mature form. The mature segment has one potential N-linked glycosylation site plus four cysteines which likely form two intra-chain disulfide bridges. Mature rat IL-10 shows 76%, 73%, 72%, 80%, 86%, 85% and 76% aa identity to guinea pig, mouse, human, feline and equine IL-10, respectively. Upon activation, mammalian cells known to secrete IL-10 include NK cells, cytotoxic CD8+ T cells secreting Th2-like cytokines, CD4+CD45RA- (memory) Th1 and Th2 cells, macrophages, monocytes, CD5+ and CD5- B cells, dendritic cells, hepatic stellate (Ito) cells, keratinocytes, melanoma cells, mast cells, placental cytotrophoblasts, and fetal erythroblasts.
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