Delineation of determinants on HLA-B7 and HLA-B27 that are necessary for cytolytic T cell recognition by using inter- and intra-domain recombinants.

We have used bulk culture HLA-B7 and HLA-B27 specific CTL lines derived from 11 donors, and a series of rHLA-B7/HLA-B27 genes transfected into and expressed on the surface of the murine cell P815, to determine the amino acid residues on these HLA class I molecules that are critical for allospecific CTL recognition. The results obtained indicate that for four of six HLA-B7-specific CTL lines the alpha-1 domain for CTL recognition. Furthermore, we found that residues 77 and/or 80 had a critical effect on recognition for all of the CTL lines tested. The region 97-156 in the alpha-2 domain was also important for some of these CTL lines. Furthermore, by using five bulk culture HLA-B27-specific CTL lines we were able to show that residues 77 and/or 80 and residue 152 are also essential for recognition of HLA-B27 by HLA-B27-specific CTL. The strong influence exerted by these residues is discussed in terms of the three-dimensional structure of class I molecules. Finally, a selection was regularly observed in the bulk cultures such that the CTL that were preferentially influenced by either the alpha-1 or the alpha-2 domain were lost after 4 to 7 wk of culture resulting in CTL cell lines which were extremely sensitive to sequence modifications of HLA-B7 or HLA-B27. The possible reasons for this selection, which we have previously observed with both anti-HLA-A2 and anti-HLA-A3 cell lines and is therefore not unique to HLA-B7 or HLA-B27, are discussed.