LILRB3 is a member of LILRB family that is restrictively expressed on myeloid cells, including monocytes, neutrophils, eosinophils, and basophils (as well as on in vitro differentiated mast cells and osteoclasts). LILRB3 contains four cytoplasmic ITIM motifs hat may contribute to negative regulation of immune response. Ligation of LILRB3 in human myeloid cells led to inhibition of immune activation. LILRB3 may be an inhibitor of allergic inflammation and autoimmunity. However, the ligand for LILRB3 has not been identified, and the downstream signaling of LILRB3 is unclear. It is noteworthy that LILRBs, including LILRB3, are primate specific.
LILRB3 is also expressed on some myeloid leukemia, B lymphoid leukemia, and myeloma cells. It is reportedly co-expressed with stem cell marker CD34 and with myeloma marker CD138.