TAP1 and neoplasm: In the coculture system, we found that transient overexpression of Tap1/2 could efficiently rescue the downregulation of MHC-I expression in the tumor cell surface and that the reduced proportions of IFN-γ+CD8+ and TNF-α+CD8+ T cells in OT-I splenocytes induced by Map3k1 mutation (Supplemental Figure 6, C and D and Supplemental Figure 6, E–H), which validated the key role of Tap1/2 in the modulation of tumor antigen presentation impacted by Map3k1.