MAJOR HISTOCOMPATIBILITY COMPLEX CLASS II-ASSOCIATED PEPTIDES CONTROLTHE PRESENTATION OF BACTERIAL SUPERANTIGENS TO T-CELLS

Recent studies have shown that only a subset of major histocompatibili ty complex (MHC) class II molecules are able to present bacterial supe rantigens to T cells, leading to the suggestion that class II-associat ed peptides may influence superantigen presentation. Here, we have ass essed the potential role of peptides on superantigen presentation by ( a) analyzing the ability of superantigens to block peptide-specific T cell responses and (b) analyzing the ability of individual peptides to promote superantigen presentation on I-A(b)-expressing T2 cells that have a quantitative defect in antigen processing. A series of peptides is described that specifically promote either toxic shock syndrome to xin (TSST) 1 or staphylococcal enterotoxin A (SEA) presentation. Where as some peptides promoted the presentation of TSST-1 (almost 5,000-fol d in the case of one peptide), other peptides promoted the presentatio n of SEA. These data demonstrate that MHC class II-associated peptides differentially influence the presentation of bacterial superantigens to T cells.