Epitopes on HLA-DQw3 Molecules Recognized by T-Lymphocyte Clones

The DQ region encodes HLA molecules where three different allo-specificities, DQw1, DQw2, and DQw3, may be recognized by antisera. The DQw3 antigen, found on DR4, −5, −7, −w8, and −w9 haplotypes, can be divided into DQw7 and DQw8 and w9 by restriction fragment length polymorphism (RFLP) analysis and certain monoclonal antibodies (MAb) (1). To study epitopes on DQw8 molecules that may be recognized by T cells, T-lymphocyte clones (TLCs) were generated in a mixed lymphocyte culture (MLC) in a combination identical at the DR loci, but differing for DQw8. Four CD4+ TLCs define epitopes on DQ molecules exclusively expressed by DR4,DQw8 haplotypes, but not by DR7,DQw9 or DRw9,DQw9 haplotypes. When the reactivity of these TLCs is compared with published HLA sequence data, the results indicate that residue 57 of the DQ β chain most probably is involved in the fine specificity of these T-lymphocyte clones.