A T cell clone defining a common DP/DR determinant in strong linkage disequilibrium with HLA‐A9

Clone F-7 was generated by limiting dilution of lymphocytes stimulated by allogeneic PBL on MLC. Priming against the A23, Cw6, B45, DR7, DRw53, DQw2 haplotype was performed between two HLA haploidentical first degree relatives. The clone was tested for its ability to proliferate in response to a panel of 38 homozygous B lymphoblastoid cell lines plus three local T cell lines. It showed a pattern of reactivity corresponding to HLA-A9 specificity (r= 1) and presented a concomitant cytotoxic activity. Phenotypically, this clone consisted entirely of CD4 cells, as determined by indirect immunofluorescence. Its reactivity was completely blocked by anti-DR (GSP4.1, PL8, L243) and anti-DP (B7/21, PL15) Mo-Abs, whereas anti-DQ (1A3, TU22) and anti-class I (w6/32, BB7.7) Mo-Abs and anti-A9 antibodies did not inhibit its reactivity. These results may suggest that clone F-7 could recognize a DP specificity sharing common determinants with DR, which occurs in linkage disequilibrium with HLA-A9.