Killer-cell immunoglobulin-like receptor–Human leukocyte antigen class I complex (KIR–HLA class I complex)

The Killer-cell immunoglobulin-like receptor–Human leukocyte antigen class I (KIR–HLA class I) complex is a critical regulatory axis in the innate immune system, primarily governing the activity of natural killer (NK) cells and certain T cell subsets. KIRs are a diverse family of receptors expressed on NK cells that recognize specific HLA class I molecules on the surface of target cells. This interaction typically delivers inhibitory signals that prevent NK cells from attacking healthy 'self' cells, a process essential for maintaining self-tolerance. However, many tumor cells exploit this mechanism by maintaining HLA expression to evade immune detection, effectively using the KIR–HLA interaction as an immune checkpoint. In the context of oncology, the KIR–HLA complex has become a significant therapeutic target for monoclonal antibodies designed to block inhibitory KIRs. By disrupting the binding between inhibitory KIRs and their HLA ligands, these drugs aim to 'release the brakes' on NK cells, restoring their ability to identify and destroy malignant cells. Beyond cancer, variations in KIR and HLA gene combinations are linked to susceptibility to viral infections, autoimmune disorders, and reproductive complications like preeclampsia. Understanding the structural and functional nuances of this complex is vital for developing next-generation immunotherapies that can precisely modulate innate immune responses.

Other names

KIR-MHC class I complexCD158-HLA complexNK cell receptor-HLA complexKiller cell inhibitory receptor-HLA complex

Checkpoint inhibition by blocking inhibitory KIR receptors (such as KIR2DL1, KIR2DL2, and KIR2DL3) from binding to their HLA-C ligands, thereby preventing the 'off' signal and enhancing natural killer (NK) cell-mediated lysis of tumor cells.