The novel findings that antigen-specific T cells are deficient in number and in function in ΔY mice following Listeria infection in vivo demonstrates that development of functional Ag-specific T cells is severely impaired following infection due to the MHC I cytoplasmic tail mutation and implies a dependence on MHC I targeting and cross-presentation of bacterial antigens for loading and subsequent priming of CD8 T cells. Here, CD8A is linked to listeriosis.