large transmembrane, polymorphic glycoproteins noncovalently associated with nonpolymorphic beta 2-microglobulin; in humans, three structural genes on chromosome 6 code for the HLA-A, HLA-B and HLA-C antigens, and in mice three genes on chromosome 17 code for the H-2 antigens; class I antigens are found on most nucleated cells, are recognized during graft rejection, restrict cell-mediated lysis of virus infected cells, and are associated with rheumatologic diseases and certain malignant disorders.
