An intact IL-21/IL-21R signaling axis is required for host protection against colon <i>Citrobacter rodentium</i> infection.

A. Bacterial burden and B. infection kinetics in the feces of Il21r-/- mice and WT controls shown as colony forming unit (CFU)/g feces. The results are the Mean ± SEM of 5–13 mice per group pooled from two of four independent experiments with similar results. The dashed line represents the sensitivity of the culture method. *p p U test. C. Representative colonic pathology as assessed by hematoxylin and eosin (H&E) staining (5×). The scale bar, 300 μm. D. Inflammation scoring of distal colon of Il21r-/- mice and WT controls at 9 days after infection with C. rodentium. Data are the Mean ± SEM from two pooled independent experiments with a total of 9 (Il21r-/-) or 10 (WT) mice/group. *p U test. E. Histological scoring of crypt hyperplasia in distal colon of Il21r-/- mice and WT controls at 9 days after infection with C. rodentium. Data are representative of one of two independent experiments with a total of 5 (Il21r-/-) or 5 (WT) mice/group. *p U test. F. The absolute numbers of immune subsets in the whole colon LP of Il21r-/- mice and WT controls at 3 days p.i. Data are the Mean ± SEM of absolute numbers of immune cell types, analyzed by Mann-Whitney U test.