MHC class I antigen (HLA-B27)

HLA-B27 is an allele on the B site of human leukocyte surface antigen, belonging to the type 1 histocompatibility antigen (MHC) gene. MHC can be divided into two categories: classical MHC and non classical MHC. Classic MHC includes MHC I, MHC II, and MHC III genes, which respectively encode MHC I molecules, MHC II molecules, and MHC III molecules. MHC class I antigen is a part of the classical MHC, specifically referring to proteins encoded by MHC I genes that are located on the cell surface and participate in the recognition and response of the immune system. MHC class I antigens play a crucial role in the immune system by presenting endogenous antigens to CD8+ T cells, thereby initiating adaptive immune responses.