CD8A and neoplasm: To test whether the CD28 PYAP domain is also important for CD8+ T-cell-mediated antitumor immunity, OT-I TCR-transduced WT, CD28AYAA knock-in, and CD28Y170F knock-in CD8+ T cells (Supplementary Fig. 3C) were adoptively transferred into E.G7-OVA/EL4 tumor-bearing mice, as shown in Fig. 1I.