Human interleukin 35 (IL-35) consists of the IL-12 subunit alpha and the IL-27 subunit beta which is also known as EBI3. It plays a role in immune suppression and is produced by regulatory T cells and macrophages. IL-35 suppresses effector T cell proliferation, inhibits Tʜ17 cell development, and promotes the conversion of T cells and B cells into regulatory T and B cells. Additionally, it is involved in regulation of tumor growth, autoimmune disease, and infectious tolerance.