LILRB1 (leukocyte immunoglobulin-like receptor B1) is an inhibitory immune checkpoint receptor that recognizes HLA class I molecules and suppresses immune responses. The receptor binds to a broad spectrum of HLA-A, HLA-B, HLA-C, HLA-G, and HLA-F alleles, with ligand binding resulting in inhibitory signals and down-regulation of immune responses 1. LILRB1 functions as a phagocytosis checkpoint on macrophages by recognizing HLA class I as a 'Don't Eat Me!' signal, similar to CD47, thereby impairing phagocytic uptake of cancer cells 2. In tuberculosis, LILRB1 serves as a critical checkpoint receptor that drives NK cell exhaustion through interaction with HLA-G expressed on Mtb-infected macrophages, inhibiting MAPK signaling via tyrosine phosphatases SHP1/2 3. The receptor is expressed on various immune cells including macrophages and cytotoxic lymphocytes, and contributes to immune tolerance regulation 4. LILRB1 has significant clinical relevance, as it represents a promising target for cancer immunotherapy by blocking the HLA class I:LILRB1 axis to promote phagocytosis and enhance cytotoxic functions 2. Additionally, LILRB1 polymorphisms show protective effects against spontaneous abortion, highlighting its role in reproductive immunology 5.