TAP2 and cancer: 5G-I, IL-4 alone only slightly reduced the T-cell killing in control/unstimulated A549 cells, but almost totally suppressed the tumor antigen-specific killing induced by proinflammatory cytokines. IL-4 treatment of TAP2 knockout A549 cells only slightly affected the levels of surface HLA-A2-HER2369-377 or HLA-A2-MAGE3271-279 peptide complexes and the CD8+ T-cell killing, and produced a comparable effect in parental and in TAP2 knockout cancer cells with TAP2 re-expression (Supplementary Figs. S9C-H).