That, along with our observation of reduced CD5 on T cells within the tumor microenvironment and our previous report that experimental reduction of CD5 leads to increased CD8+ T cell activation (25), collectively suggest that T cells with low CD5 within tumors (due wholly or in part to the poorly immunogenic 4T1 tumor microenvironment) may have increased sensitivity to poorly immunogenic 4T1 tumor antigens. This evidence concerns the gene CD8A and neoplasm.