CD8A and neoplasm: Incidentally, 5 × 3 Gy fractionated irradiation of B16 melanoma produced slightly more tumor infiltration than a single dose of 15 Gy for CD8+ T cells activated by tumor-derived peptide presented on MHC class II, whereas 1 × 15 Gy produced higher numbers of cells activated by peptide presentation on MHC class I (67).