Does a Low Level of Expression of HLA Molecules Engender Autoimmunity?

The immune system can summon a variety of defenses against invaders from the outside. Among these deterrents are three types of killer lymphocytes that attack and lyse cellular targets. One type consists of cytotoxic, or CD8, T cells with α/β antigen receptors that interact with the HLA class I glycoproteins on nearly all cells. These HLA molecules bind to peptides derived from intracellular antigens, such as viral proteins, and display them on the cell surface. Binding of the α/β antigen receptor to complexes of HLA class I molecules and peptide fragments of an invading virus induces the T lymphocyte to . . .