Interleukin 10 (IL-10) is a homodimer consisting of 2 subunits 178 amino acids long. In humans, it is encoded by the IL-10 gene located on chromosome 1 and consists of 5 exons.IL-10 is secreted mainly by monocytes and to a lesser extent by lymphocytes, type II helper T-cells (Th2), mast cells, CD4+CD25+Foxp3+ regulatory T-cells, and partially activated T-cells and B-cells. It has multiple effects on immune regulation and inflammation. It down-regulates Th1 cytokines, class II MHC antigens and co-stimulatory molecules in macrophages. It also enhances B cell survival, proliferation and antibody secretion.IL-10 blocks NF-κB activity and is involved in the regulation of the JAK-STAT signaling pathway.The immunosuppressive properties of IL-10 suggest a possible clinical application to inhibit rejection after organ transplantation.IL-10 also possesses strong anti-inflammatory properties.