Protective T cells in the immune system discriminate between self and non-self tissues, through the T cell receptor (TCR). Small protein fragments (peptides) known as "minor antigens" and found on the cell surface are recognized by T cells as either self or non-self, which can trigger a T cell-mediated immune response. These minor antigen peptides originate from within the cell, processed from protein precursors and presented by the major histocompatibility complex, giving T cells powerful immunosurveillance capabilities. Despite high TCR specificity, T cells recognize orthologue antigens, aka xenoantigens, from other species. As little is known regarding species-specific differences in antigen processing and presentation, a better understanding of the rules governing xenoantigen processing, presentation and T cell recognition is needed. Findings by the PI and others have shown that mouse cytotoxic T lymphocytes (CTLs) raised against specific mouse minor histocompatibility antigens (e.g. H4 and H7) recognize human orthologue minor antigens. However, when extended to mouse CTLs specific for the hydrophobic H47 antigen, such human cells were not recognized. Preliminary results indicate that these human cells transcriptionally express a "human H47-like" gene. Moreover, the predicted human H47 protein contains a peptide motif similar to the mouse H47 peptide antigen; when synthesized and loaded onto cells in a CTL lysis immunoassay, the mouse CTLs recognized this human peptide as foreign and killed the cells. This project will determine the molecular basis of this species-specific H47 antigen processing/presentation difference i.e. whether the species discrepancy is based in sequence/cleavage, or if human cells lack specific antigen processing machinery needed to ultimately present this particular antigen precursor. Students enrolled in research-related courses or in the new B.S. Biotechnology major at this small liberal arts university will confirm human H47 translational expression using western blotting, will construct H47-based mini-genes, and will transfect human and murine cells with the H47-based expression constructs as well as murine antigen processing gene constructs. CTL testing of transfectant cells will identify H47 processing and presentation status. Undergraduate student participation in this research will provide technical and conceptual expertise, and will prepare the student researchers for careers in modern science.
