CD4 ⁺ T cells initiate intestinal inflammation in P440S mice. (A and B) Frequencies of CD4⁺CD69⁺ and CD4⁺PD-1⁺ T cells from mesLN. (C) Frequency of IFNγ-producing lamina propria CD4⁺ T cells. (D) Whole spleen masses from P440S mice that received CD4-depleting mAb (GK1.5 mAb) or isotype mAb. (E and F) Gross (E) and H&E histological (F) images of large intestines from untreated P440S mice, isotype-treated P440S mice, or CD4-depleted P440S mice. (G) Ratios of colon length and mass. (H and I) Average crypt length (H) and number of lymphoid aggregates per histological section (I) from H&E histology. (J) Cytokine concentration from colon culture supernatants. All measurements were taken from mice at 20-wk of age. Length of scale bar in E is 1 cm. Length of bars in F is 200 μm. Experiments in A and B are representative of results from three independent experiments with 4–11 mice per group. Experiments in C–J are representative of results from two independent experiments with 3–10 mice per group. Error bars represent the median and 95% CI. *P < 0.05, **P < 0.01, ***P < 0.001. Not significant unless stated by asterisk in figure. Kruskal–Wallis accounting for multiple comparisons was used for statistical significance testing for experiments in A–C and J. Unpaired t test between P440S (isotype) and P440S (anti-CD4) was used to test for statistical significance for experiments in D and G–I.