Transport protein genes in the murine MHC: Possible implications for antigen processing (Reprinted from Science, vol 250, pg 1723-1726, 1990)

T lymphocyte activation requires recognition by the T cell of peptide fragments of foreign antigen bound to a self major histocompatibility complex (MHC) molecule. Genetic evidence suggests that part of the class II moon of the MHC influences the expression, in trans, of MHC class I antigens on the cell surface, by regulating the availability of peptides that bind to and stabilize the class I molecule. Two closely related genes in this region, HAM1 and HAM2, were cloned and had sequence similarities to a superfamily of genes involved in the ATP-dependent transport of a variety of substrates across cell membranes. Thus, these MHC-linked transport protein genes may be involved in transporting antigen, or peptide fragments thereof; from the cytoplasm into a membrane bounded compartment containing newly synthesized MHC molecules.