Figure 1.

ALDH activity is enriched in the small intestine LP and is largely restricted to CD103⁺ DCs. To assess which compartment contained the largest population of cells with the ability to generate ATRA, and by extension, where this ATRA generating capacity may be imprinted, cellular populations were isolated from intestinal and systemic compartments and evaluated for the presence of ALDH activity using the flow cytometric based Aldefluor assay. A: The small intestine LP contained a substantially larger population of ALDH⁺ cells when compared with all other intestinal and non-intestinal compartments. B: Analysis of the LP ALDH⁺ cells revealed that the majority of this population was CD45⁺ MHCII⁺ CD11c⁺ CD103⁺, consistent with CD103⁺ DCs. LP cellular populations treated with DEAB, an ALDH inhibitor served as a control to set the gate for positive staining. C: Among CD103⁺ DCs, those from the small intestine LP were significantly more likely to be ALDH⁺, indicating the differences in the ALDH⁺ populations from each tissue are not solely due to differences in the size of the CD103⁺ DC populations. Col, colonic LP; LN, peripheral lymph node; MLN, mesenteric lymph node; PP, Peyer's patch; SI, small intestine LP; Spl, spleen. n = 2 in A and C. Data in B are representative of 1 of 8 experiments. *P < 0.05.