CX3CR1 and CD103 characterize distinct sets of LP mononuclear cells. (A) 50-µm cryosections of CX3CR1^+/GFP mice were stained for CD11c and CD103 and analyzed by confocal microscopy. The image shows an orthogonal projection of a 7.5-µm z-stack depicting CX3CR1/GFP (green), CD103 (red), and CD11c (blue). The boxed region is shown in detail in split channels. The dashed lines indicate the epithelial border/basal lamina. Bar, 10 µm. The localization of CX3CR1/GFP⁺ and CD103⁺CD11c⁺ cells in the proximal ileum with respect to the basal epithelium and their numbers were determined using 7-µm-thick cryosections documented by epifluorescence microscopy. Diagrams depict mean and 25th and 75th percentiles as boxes. Sections obtained from four mice in two independent experiments were evaluated and a total of 116 CD103⁺ and 584 CX3CR1⁺ cells were analyzed. ***, P < 0.001. (B) Flow cytometric analysis of CX3CR1^+/GFP LPCs. CD103⁺ DCs express very low levels of CX3CR1 and were identified by subgating the CD103⁺CX3CR1^−/low population on CD11c⁺MHCII⁺ cells. CD11c^low/−MHCII⁻ cells in this plot are removed when gating on CD3⁻CD19⁻ cells, suggesting they are T cells (not depicted). CX3CR1⁺ LPCs could be further subgrouped into CX3CR1^int and CX3CR1^high LPC populations. All three populations were analyzed for expression of CD11b and F4/80. Numbers indicate mean percentage (SD) of cells in the respective gate of 10 mice analyzed in at least four independent experiments. The total percentage of CD103⁺ DC among CD45⁺ cells is 1.9% (SD, 1).