CD300LB, also known as CD300b, LMIR5, CLM-7, and IREM-3, is a glycoprotein member of the immunoglobulin superfamily. LMIR5 is expressed on the surface of myeloid lineage cells. It forms noncovalent cis-homodimers and cis-heterodimers with other CD300 family proteins, and the composition of these dimers affects the cellular response. Antibody cross-linking of LMIR5 induces mast cell granule release and cytokine production as well as its tyrosine phosphorylation of LMIR5 (in human). LMIR5 interacts with TIM1 and TIM4 which regulate T cell activation and are themselves binding partners. TIM1 interactions with LMIR5 mediate mast cell activation and the accumulation of neutrophils at sites of TIM1 up-regulation on damaged renal tubule epithelial cells. Acts as an activating immune receptor through its interaction with ITAM-bearing adapter TYROBP, and also independently by recruitment of GRB2.
