Peptides recognized by class I restricted T cells also bind to MHC class II molecules.

The mechanisms of antigen recognition employed by both class I and class II MHC-restricted T cells are very similar, yet many of the T cell determinants described to date are recognized in the context of a single class of MHC molecules, and generally with only one or a very few different MHC alleles. To determine whether this might be due to a structural difference between class I and class II restricted T cell determinants, peptides previously shown to be recognized in the context of MHC class I proteins by mouse or human CD8+ T lymphocytes were tested for their capacity to bind to HLA-DR molecules on the surface of B lymphoblastoid cell lines (B-LCL). Four out of five class I restricted T cell determinants tested bound to a panel of B-LCL, and the binding was inhibited by anti-HLA-DR mAb. The peptides did not bind to the class II-negative B-LCL RJ2.2.5 nor to mouse L cells, but did bind to L cells transfected with HLA-DR1.