HLA-class I major histocompatibility (MHC) antigens are intrinsic membrane glycoproteins expressed on nucleated cells and noncovalently associated with an invariant beta2 microglobulin. They carry foreign determinants important for immune recognition by cytotoxic T cells, thus important for anti-viral and anti-tumour defence. Human HLA-class I antigens are represented by HLA-A, HLA-B and HLA-C molecules.
