Evidence that autoreactive T hybridomas recognize multiple epitopes on the I-Ak molecule

In this study we attempt to define the number of determinants on the I-Ak molecule recognized by a panel of autoreactive I-Ak-specific T cell hybridomas. The recognition sites or histotopes of a panel of autoreactive I-Ak-restricted T cell hybridomas was determined in two ways: 1) by their ability to be activated by a panel of A betak and A alphak mutant antigen-presenting cell lines, and 2) by inhibition of activation by anti-I-Ak monoclonal antibodies. The results are most consistent with the presence of multiple distinct recognition sites on the I-Ak molecule. However, an alternative explanation, that the T cell hybridomas recognize the same self epitope on Class II molecules, but with different affinity, cannot be excluded.