FIGURE 9.

(A) LTβ^−/− × RAG^−/− double-deficient mice are devoid of PPs, MLNs, and most peripheral lymphoid tissue. LTβ^−/− × RAG^−/− double-deficient mice were generated by interbreeding RAG^−/− mice with LTβ^−/− animals (both on the C57Bl/6 background) to generate LTβ^−/− × RAG^−/− or their LTβ ^+/+ × RAG^−/− littermate controls. Mice were injected (ip) with 5 × 10⁵ CD45RB^high T cells (RB^high) to induce colitis. Inspection of mice at 2–3 weeks post-T-cell transfer revealed that LTβ^−/− × RAG^−/− mice were devoid of PPs and MLNs (right panels) as well as lymphoid follicles and most peripheral lymph nodes (not shown), whereas their littermate controls contained developing/residual PPs (red circles) and MLNs similar to RAG^−/− (black circle). (B) Adoptive transfer of naive T cells into LTβ^−/− × RAG^−/− or LTβ^+/+ × RAG^−/− induces chronic colitis. At 2–3 weeks following T-cell transfer, mice were euthanized and their colons scored in a blinded fashion using our published scoring criteria²⁷; n = 3 mice for each group.