Figure 4. MHCII expression by epithelial cells is required for CD4⁺CD8αα⁺ IEL differentiation.

(A-C) Flow cytometry analysis of the intestinal epithelium (IE) of iVil1^WT(MHCII) (H2-Ab1^+/+ Vil1^creERT2+/− or H2-Ab1^f/f Vil1^{creERT2−/−}) and iVil1 ^Δ(MHCII) (H2-Ab1f/f Vil1^creERT2+/+) mice after tamoxifen administration to mice of different ages as indicated. Dot plots of surface CD8α and TL-Tetramer expression among CD4⁺ T cells (left). Frequencies of CD4⁺CD8αα⁺ IELs (CD4⁺CD8α⁺TL-Tetramer⁺) or Foxp3⁺ regulatory cells (Treg) among CD4⁺ T cells (middle). Frequencies of pre-IELs (CD4⁺CD103⁺) among CD4⁺SP (CD4⁺CD8α⁻Foxp3⁻) cells and frequencies of total CD4⁺ cells among TCRαβ⁺ cells (right). Data are expressed as mean +/− SEM of individual mice (n=7–15, 3–6 independent experiments per timepoint). Significant p values as indicated [student’s t test (A-C)]. See also Figure S4.