May act as receptor for class I MHC antigens. Becomes activated upon coligation of LILRB3 and immune receptors, such as FCGR2B and the B-cell receptor. Down-regulates antigen-induced B-cell activation by recruiting phosphatases to its immunoreceptor tyrosine- based inhibitor motifs (ITIM). . This is the function of Ensembl gene identifier ENSG00000204577 (LILRB3, leukocyte immunoglobulin like receptor B3).