Ontogeny of synonymous T cell populations with specificity for a self MHC epitope mimicked by a bacterial homologoue: an antigen-specific T cell analysis in a non-transgenic system

By means of a novel technique for identification and isolation of MHC class II-restricted antigen-specific T cells, we describe here in non-transgenic BALB/c mice physiological positive selection of an oligoclonal population of T cells which recognizes both a self MHC-derived peptide (I alpha 52) an d a bacterial homologoue (Hi15). The results support a model for self pepti de-mediated generation of T cells which have specificity for microbial anti gens through molecular mimicry. This mechanism may be a model for the ontog eny of a physiological T cell response to infectious agents. Loss of contro l of these circuits may be part of the inciting factors of autoimmunity.