Effects of IL-21^−/− CD25⁻ T cells on cytokine and cytolytic Teff molecule production. Lethally irradiated recipients were injected with 2 × 10⁶ wt of IL-21^−/− CD25⁻ T cells (triangles) or injected with 2 × 10⁶ FoxP3⁻ T cells and treated with irrelevant IgG or anti–IL-21 (diamonds). Colon lamina propria cells were isolated on day 14 and analyzed by FACS and the frequency of CD4⁺ cells expressing IFNγ (A), IL-4 (B), and IL-17 (C) is shown. The frequency of granzyme B (D) or TNFα (E) was determined on CD4⁺ (triangles) and CD8⁺ (diamonds) T cells. The frequency of CD4⁺ and CD8⁺ T cells coexpressing IFNγ/TNFα (F) or expressing FasL (G) is shown. P values are indicated. Data from 2 experiments (A,C) or 1 experiment (B,D-G) with 6 mice per group total.