Co-caged and littermate mice develop equally exacerbated T cell–induced colitis. (A and B) Co-caged (A) and littermate (B) Rip2^−/−Rag1^−/− and Rip2^+/+Rag1^−/− mice were injected i.p. with 0.5 × 10⁶ CD45RB^High CD4 T cells and sacrificed at week 4. Colons were fixed, H&E stained, and scored for colitis severity. Data from three experiments were pooled. Mean ± SEM is shown, and an unpaired Student’s t test was performed. (C) Proximal colon explants from week 4 after transfer littermate mice were cultured for 18 h, and supernatants were analyzed by ELISA for cytokine production. Data from two experiments were pooled with five to six samples per group. Mean ± SEM is shown, and a Student’s t test was performed. (D–F) Rag1^−/− mice were orally gavaged with 10⁶ PFU MNV CR6 or MNV CW3 and 2 wk later injected i.p. with 0.5 × 10⁶ CD45RB^High CD4 T cells. (D) Body weight was monitored, and mice were sacrificed at week 4. (E) Colons were fixed, H&E stained, and scored for colitis severity. (F) Fecal pellets were confirmed positive by qPCR. Data are from one experiment with three to four mice per group. Mean ± SEM is shown, and a one-way ANOVA was performed.