Antigens presented to CD4+ T cells derive primarily from exogenous proteins that are processed into peptides capable of binding tc class II major histocompatibility complex (MHC) molecules in an endocytic compartment1-4. In contrast, antigens presented to CD8+ T cells derive mostly from proteins processed in the cytosol, and peptide loading onto class I MHC molecules in an early exocytic compartment is dependent on a transporter for antigen presentation encoded in the class II MHC region5-11. Endogenous cytosolic antigen can also be presented by class II molecules12,13. Here we show that, unlike class I-restricted recognition of antigen, HLA-DR1-restricted recognition of cytosolic antigen occurs in mutant cells without a transporter for antigen presentation. In contrast, DR1-restricted recognition of a short cytosolic peptide is dependent on such a transporter. Thus helper T-cell epitopes can be generated from cytosolic antigens by several mechanisms, one of which is distinct from the classical class I pathway.
|Number of pages||3|
|Publication status||Published - Jun 25 1992|
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