Figure 4.

Epithelial CRBPII plays a critical role in imprinting CD103⁺ LP DCs with ALDH activity. A–C: To evaluate a role for CRBPII in imprinting LP DCs, LP cellular populations were isolated from wild-type and CRBPII^−/− mice and evaluated for ALDH activity. CRBPII^−/− mice had a decrease in the population of ALDH⁺ LP cells (A), which correlated with a decreased level of ALDH expression in CD103⁺ LP DCs from CRBPII^−/− mice and with a decrease in the population of CD103⁺ LP DCs that are ALDH ⁺ (B and C). D: Quantitative real-time polymerase chain reaction was used to define the cellular population expressing CRBPII. CRBPII was highly expressed by small intestine epithelium, was expressed at low levels in the colonic epithelium, and was undetectable in the small intestine LP and CD103⁺ and CD103⁻ LP DCs. E andF: Bone marrow transfers confirmed the requirement for CRBPII on nonhematopoietic cells for the induction of ALDH activity on LP DCs, as transfer of wild-type bone marrow into CRBPII^−/− mice resulted in a significant reduction in the population of ALDH⁺ LP DCs, whereas conversely, transfer of CRBPII^−/− bone marrow into wild-type recipients resulted in an ALDH⁺ LP DC population that was equivalent to the transfer of wild-type bone marrow into wild-type recipients. G: There was no significant difference in the size of the LP DC population between the groups of bone marrow recipients. H and I: Evaluation of the distribution of epithelial CRBPII expression and LP DC ALDH activity in four equivalent sections of small intestine revealed a correlating proximal to distal gradient of CRBPII expression and ALDH activity in LP DCs. C epi, colon epithelial cells; NS, not significant; SI, full-thickness small intestine; SI epi, small intestine epithelial cells; SI LP, small intestine LP. *P < 0.05. n = 4 for data in A–C, H, and I, n = 3 for data in E–G; data are representative of one of two experiments in D.