THE MONOCLONAL-ANTIBODY HCA2 RECOGNIZES A BROADLY SHARED EPITOPE ON SELECTED CLASSICAL AS WELL AS SEVERAL NONCLASSICAL HLA CLASS-I MOLECULES

HCA2 is a widely used monoclonal antibody. thought to be highly select ive for HLA-A and -G heavy chains. We demonstrate here that it also sh ows affinity to HLA-B73 and HLA-E molecules on intact cells. By compar ing the differences in the amino acid (AA) sequences of several HLA cl ass I alleles that are either recognised or not recognised by HCA2, a likely epitope of HCA2 has been deduced. It extends from position 76 t o position 83 of the alpha(1)-domain. In intact cells, the solvent-exp osed AA in positions 76 (Ala, Val or Met), 80 (Asn or Thr) and 83 (Gly ) are likely to constitute the recognition region. Inhibition experime nts with peptides spanning the region of the alpha(1)-domain from posi tion 74 to 85 of various HLA class I heavy chains prove that HCA2 reco gnizes a broadly shared epitope on HLA-E, -F and -G molecules as well as selected HLA-A, -B and -C antigens. (C) 1998 Elsevier Science Ltd. All rights reserved.