Leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4) is also known as CD85 antigen-like family member K (CD85K), Immunoglobulin-like transcript 3 (ILT-3), Leukocyte immunoglobulin-like receptor 5 (LIR-5), Monocyte inhibitory receptor HM18, which belongs to the leukocyte immunoglobulin-like receptor (LIR) family. LILRB4 / CD85K contains 2 Ig-like C2-type (immunoglobulin-like) domains. CD85K is detected in monocytes, macrophages, dendritic cells, lung, natural killer cells and B-cells. LILRB4 / CD85K is receptor for class I MHC antigens. CD85K recognizes a broad spectrum of HLA-A, HLA-B, HLA-C and HLA-G alleles, involved in the down-regulation of the immune response and the development of tolerance. LILRB4 interferes with TNFRSF5-signaling and NF-kappa-B up-regulation and inhibits receptor-mediated phosphorylation of cellular proteins and mobilization of intracellular calcium ions.