On the relative immunogenicity of DR alloantigens: T cell recognition of HLA-DR2a and HLA-DR2b.

The HLA-DR2 haplotype encodes two highly polymorphic DR molecules, DR2a and DR2b. Because little is known regarding the relative immunogenicity of different HLA-DR molecules, we have studied the T-cell recognition of DR2a and DR2b molecules from the DRw15, Dw2 haplotype. A series of DR2-specific alloreactive T-cell clones were analyzed with murine L-cell transfectants expressing either the DR2a or the DR2b molecules as stimulator cells in proliferation assays. Somewhat surprisingly, both DR2a and DR2b were capable of stimulating DR2-specific T-cell clones with equal magnitude and similar frequency. In addition, DR2a and DR2b are functionally distinct, that is, no clone was identified which was stimulated by both DR2a and DR2b molecules.