CD85 antigen-like family member J (CD85J), also known as Leukocyte Immunoglobulin-like Receptor subfamily B member 1 (LILRB1 or LIR-1), Immunoglobulin-like Transcript 2 (ILT-2), Monocyte/macrophage Immunoglobulin-like Receptor 7 (MIR7), belongs to the Leukocyte Immunoglobulin-like Receptor (LIR) family. CD85J/LILRB1 contains 4 Ig-like C2-type (Immunoglobulin-like) domains.
CD85J/LIR-1 is mainly expressed on B cells and monocytes. CD85J is a receptor for class I MHC antigens, capable of recognizing a broad spectrum of HLA-A, HLA-B, HLA-C, and HLA-G alleles, as well as being a receptor for H301/UL18 (a human cytomegalovirus class I MHC homolog). Ligand binding leads to inhibitory signals and downregulation of immune responses. Interaction of CD85J/LILRB1 with HLA-B or HLA-E inhibits signals triggered by FCER1A and suppresses serotonin release. CD85J/LILRB1 inhibits cell protein phosphorylation mediated by FCGR1A and mobilization of intracellular calcium ions.
LILRB1 plays a central role in immune tolerance to self and non-self signals, altering differentiation programs and cytokine production capacity of DCs even after exposure to lipopolysaccharides. Additionally, LILRB1 finely tunes major cellular and immune processes by regulating immune cell activation thresholds.
