BATF KO T cells are largely intact in activation, survival, and proliferation. (A–E) WT and BATF KO CD4⁺ T cells were examined in vitro for activation (A) and survival (B) and in vivo for proliferation (C–E). T cells were activated with anti-CD3, anti-CD28, and IL-2 for 4 d, and expression of CD69 and CD62L (A) and cell death based on staining with annexin V and propidium iodide (PI; B) were examined. (C) CD45.1 mice were injected i.v. with 10 million CFSE-labeled WT or BATF KO OT-II CD4⁺ T cells and were immunized i.p. with OVA in complete Freund’s adjuvant. CFSE dilution was examined by flow cytometry 5 d later. (D) Rag1^−/− mice were injected i.v. with 10 million CFSE-labeled WT or BATF KO CD4⁺ T cells. The host mice were examined 14 d later for CFSE dilution. (E) Absolute numbers of WT and BATF KO CD4⁺ T cells expanded in the indicated organs of Rag1^−/− mice are shown. Pooled data obtained from three experiments are shown in the graphs (n ≥ 10/group). All error bars are SEM obtained from pooled data. Significant differences from WT groups are shown (*, P < 0.05).