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. In mice, three genes named K, D, and L on chromosome 17 code for the H-2 antigens. Class I antigens are found on most nucleated cells and are generally detected by their reactivity with alloantisera. These antigens are recognized during graft rejection and restrict cell-mediated lysis of virus-infected cells. They are primarily associated with rheumatologic diseases and certain malignant disorders.
