Unusual distribution of a non-classical MHC I restricted CD8+ T population

Abstract

Abstract The normal peptide repertoire presented by MHC class I molecules on the cell surface is essential for immune surveillance of intracellular pathogens. The generation of this peptide repertoire is critically dependent upon the ER aminopeptidase associated with Ag processing (ERAAP). Interestingly, ERAAP-deficient cells are recognized by a unique population of cytotoxic T cells, called QFL-T cells, that are specific for the ligand presented by the non-classical MHC molecule, Qa-1b. The QFL-T cells are similar to other non-classical MHC restricted NKT or MAIT cells in their αβ TCRs, but their physiological function(s) are unknown. To identify the potential function of QFL-T cells, we assessed the expression of the Qa-1b restricted ligand as well as the distribution of QFL-T cells in various tissues. We found the ERAAP-dependent Qa-1b restricted ligand as well as the QFL-T cells were highly expressed in the intestine. Remarkably, relative to wild-type mice, the overall number and frequency of QFL-T cells among the intraepithelial lymphocytes(IELs) decreased significantly in the germ-free mice whereas the splenic QFL-T population remained unaffected. These findings suggest a role for gut-microbiota in the homing/maintenance of the QFL-T cells in the intestine.