IL-10 is a homodimeric cytokine mainly produced by CD4
+ Tʜ2 cells, regulatory T cells (Treg), Ly-1 B cells, and keratinocytes. IL-10 is regarded as a regulator of the development of Ly-1 B cells and inhibits the synthesis and secretion of many cytokines. Expression of IL-10 in the islets of Langerhans cells of transgenic mice has been shown to lead to a pronounced inflammation of the pancreas. Knockout mice lacking IL-10 are growth retarded, anemic, and suffer from chronic local bowel inflammations. Like IL-4, it enhances the humoral immune response and lessons cell mediated immune reactions. Mouse IL-10 shares 73% amino acid sequence homology with human IL-10 and is able to block the binding of human IL-10 to mouse cells but not to human cells.