TNFR1 expression is needed neither for T-cell imprinting nor for T-cell effector functions. (A-D) Proliferation and IFN-γ production by TNFR1^+/+ or TNFR1^−/− Th1 and Tc1 cells. (A-B) TNFR1^+/+ (■) or TNFR1^−/− () TNCB-specific T cells (10⁵) of the indicated origin were stimulated for 24 hours with 5 × 10⁵ hapten-modified APCs. [³H] thymidine was added for the final 6 hours. (C-D) TNFR1^+/+ (■) or TNFR1^−/− () T cells (10⁵) from the indicated origin were stimulated for 24 hours with 5.0 × 10⁵ hapten-modified APCs. Supernatants were harvested after 24 hours, and the IFN-γ content was determined by enzyme-linked immunosorbent assay. (E-F) Efficient DTHRs require TNFR1-expressing resident cells. Th1 or Tc1 cell lines that were either TNFR1^−/− or TNFR1^+/+ were transferred intracutaneously into ears of naive TNFR1^−/− or TNFR1^+/+ mice, 0.5 hours before challenge with TNCB (n = 3-7). Ear swelling was determined 24 hours later.