Figure 4.
Direct 4–1BB signaling promotes CD8+ T cell effector function and proliferation in vitro. C57BL/6 wild-type (WT) mice or interferon γ (Ifn) knockout (IFNγKO) mice were challenged with 1 × 105 Eμ-myc 4242 tumor cells, some of which were then vaccinated on day 7 (n = 3 per group). Whole splenocytes (A) or MACS-purified CD8 T cells (B, C) were isolated one day post-vaccination and cultured in vitro for 3 d, supplemented with IL-2, with or without addition of 5 μg/mL anti-4–1BB monoclonal antibody (mAb). (A–B) IFNγ secretion into the culture supernatant was measured by ELISA. (C) Cell proliferation was calculated from levels of carboxyfluorescein succinimidyl ester (CFSE) dilution indicated as the percentage of CFSE low cells relative to the undivided CFSE-labeled lymphocyte peak. All data show mean ± SEM; *P < 0.05; **P < 0.01; ***P < 0.001; ns = not significant, unpaired t-test).