Leukocyte immunoglobulin (Ig)-like receptors [LILRs, also known as Ig-like transcripts (ILTs)] are a family of inhibitory and stimulatory receptors encoded within the leukocyte receptor complex and are expressed by immune cell types of both myeloid and lymphoid lineage. Several members of the LILR family recognize major histocompatibility complex class I. The immunomodulatory role of LILR receptors indicates that they may exert an influence on signaling pathways of both innate and adaptive immune systems.
Signaling mechanisms are employed that are similar to the ones adopted by the closely related killer cell inhibitory receptors (KIRs). ITIMs recruit inhibitory phosphatases that dephosphorylate ITIM and ITAM domains in order to influence intracellular signaling cascades. In contrast, activating LILRs, which lack any signaling domains of their own, rely on association with an adaptor protein such as FceRI-gamma to transmit their signal through its intracellular ITAMs.