Reduced mucosal CD4⁺ T-cell numbers within infected <i>Rag1</i>^<i>-/-</i> and <i>Retnlb</i>^<i>-/-</i> mice, leading to defective epithelial cell proliferation.

<p>(A) CD4 staining in the colons of infected <i>Rag1</i>^<i>-/-</i> mice reconstituted with either PBS or CD4⁺ T cells. (B) Ki67 staining in PBS or CD4⁺ T cell-reconstituted <i>Rag1</i>^<i>-/-</i> mice (10 DPI). Graph on right (B1): Enumeration of Ki67-labeled cells. Bars represent mean average number of Ki67⁺ cells/100 cells. Error bars = SD. *<i>P</i> < 0.01. (C) LPS staining showing deeper penetration of <i>C</i>. <i>rodentium</i> into the crypts of PBS-reconstituted <i>Rag1</i>^<i>-/-</i> mice (arrows) as compared to CD4⁺ T cell-reconstituted <i>Rag1</i>^<i>-/-</i> mice (10 DPI). Scale bar = 100 μm. Original magnification = 200X. (D) CD4 staining in uninfected or 10 DPI C57BL/6 and <i>Retnlb</i>^<i>-/-</i> mice. (E) Enumeration of CD4⁺ cells within colonic sections. Results represent means of cells counted from 5–10 high power fields (400X)/mouse. *<i>P</i> < 0.05. Error bars = SEM. (F) Flow cytometry of lamina propria lymphocytes purified from infected C57BL/6 and <i>Retnlb</i>^<i>-/-</i> mice (8 DPI). All results are representative of 2–3 independent experiments, with 3–5 mice/group.