I Antigens, Class

Membrane Glycoproteins consisting of an alpha subunit and a beta 2-Microglobulin beta subunit. In Humans, highly polymorphic Genes on Chromosome 6 encode the alpha subunits of class I Antigens and play an important Role in determining the serological specificity of the Surface Antigen. 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.