HOMOZYGOUS HUMAN TAP PEPTIDE TRANSPORTER MUTATION IN HLA CLASS-I DEFICIENCY

Human lymphocyte antigen (HLA) class I proteins of the major histocomp atibility complex are largely dependent for expression on small peptid es supplied to them by transporter associated with antigen processing (TAP) protein. An inherited human deficiency in the TAP transporter wa s identified in two siblings suffering from recurrent respiratory bact erial infections. The expression on the cell surface of class I protei ns was very low, whereas that of CD1a was normal, and the cytotoxicity of natural killer cells was affected. In addition, CD8(+) alpha beta T cells were present in low but significant numbers and were cytotoxic in the most severely affected sibling, who also showed an increase in CD4(+)CD8(+) T cells and gamma delta T cells.