IL-37 (Interleukin-37) is a member of IL-1 family and is primarily an anti-inflammatory cytokine, which reduces systemic and local inflammation. There are five different splice variants of IL-37 termed IL-37a-e, where Isoform IL-37b is the largest isoform. IL-37 has significant sequence similarity with IL-18 and highly expressed in inflammatory tissues, which inhibits the excessive inflammatory response. The expression is highly induced by several toll-like receptor (TLR) ligands and pro-inflammatory cytokines such as IL-1beta, TNF-alpha, IFN-gamma. IL-37 is a potent inhibitor of innate immunity by shifting the cytokine equilibrium away from excessive inflammation.