Leukocyte immunoglobulin-like receptor subfamily B member 2 (LILRB2), also known as ILT4, LIR2, monocyte/macrophage immunoglobulin-like receptor 10, MIR-10, and CD85d, belongs to the leukocyte immunoglobulin-like receptor (LIR) family of transmembrane glycoproteins that negatively regulate immune cell activation.LILRB2 is expressed on both innate (monocytes, macrophages, basophils, and DCs) and adaptive (CD4+ T cells) immune cells and interacts with MHC-I on nucleated cells (unknown specific ligand). LILRB2 interacts with related ligands HLA-G, ANGPTLs, SEMA4A and CD1d in tumor microenvironment, resulting in myeloid cells promoting tumor growth and enhancing tumor immune escape. It has been shown pre-clinically that LILRB2 antagonism promotes macrophage maturation and activation. MK-4830 (Merck and Agenus) is an anti-LILRB2 fully human IgG4 monoclonal antibody, and phase II clinical studies have been initiated. In addition, IO-108, JTX-8064, and NGM707 are in phase I clinical studies.