Leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4) (LILRB4)

Leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4), also known as ILT3 or CD85k, is an inhibitory receptor primarily expressed on the surface of monocytes, macrophages, and dendritic cells. It belongs to the leukocyte immunoglobulin-like receptor (LILR) family and contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in its cytoplasmic tail, which mediate inhibitory signaling upon ligand binding. LILRB4 has been identified as a critical immune checkpoint in monocytic acute myeloid leukemia (AML), where it is highly overexpressed on malignant blasts and their bone marrow precursors. In the context of AML, LILRB4 interacts with ligands such as Apolipoprotein E (ApoE) to suppress T cell activity and promote the infiltration of leukemia cells into tissues, thereby facilitating disease progression and immune evasion. Therapeutic strategies targeting LILRB4, such as the monoclonal antibody IO-202, aim to block these inhibitory signals, restore anti-tumor immune responses, and directly inhibit the growth of monocytic leukemia cells.

Other names

ILT3CD85kLIR-5HM18Leukocyte immunoglobulin-like receptor 5