Interleukin 10 (IL10)

Interleukin-10 is a small protein known as a cytokine that functions as an important regulator of the immune system.  Although IL-10 is known to have many different roles in the immune system, its two major activities include inhibition of cytokine production by macrophages and inhibition of the accessory functions of macrophages during T cell activation. The effects of these actions cause IL-10 to play mainly an anti-inflammatory role in the immune system. 

IL-10 was originally known as the cytokine synthesis inhibiting factor (CSIF), and the discovery of this protein was based on its biological activity. IL-10 is mainly produced by the Th2 subset of CD4⁺ helper cells.  However, it is also produced by some activated B cells, some Th1 cells , activated macrophages, and some nonhematopoietic sources .