Site-specific expression of CD11b and SIRPalpha (CD172a) on dendritic cells: implications for their migration patterns in the gut immune system.

Dendritic cells (DC) in the intestinal tract play a major role in directing the mucosal immune system towards tolerance or immunity. We analyzed whether different mucosal DC subsets in pigs have specific functions, localizations, or migration patterns in vivo. Therefore, we collected physiologically migrating DC by pseudo-afferent cannulation of the intestinal duct in eight Gottingen minipigs. Lymph DC were phenotypically and functionally characterized and compared to DC found on histological sections of porcine small intestine and mesenteric lymph nodes (MLN). Four different DC subpopulations were detected. Lamina propria (LP) DC were mainly CD11b(+) signal regulatory protein alpha (SIRPalpha)(+), DC in Peyer's patches were mainly CD11b(-)/SIRPalpha(+) in subepithelial domes and CD11b(-)/SIRPalpha(-) in interfollicular regions, whereas MLN DC were largely CD11b(+)/SIRPalpha(-). Of these four subsets, only the CD11b(+)/SIRPalpha(+) DC and the CD11b(+)/SIRPalpha(-) DC were present in lymph. This suggests that DC migration to MLN largely originates from the LP. Lymph DC expressed high levels of MHC class II and costimulatory molecules and had a low capacity for FITC-dextran uptake, indicating a mature phenotype. However, lymph DC did not induce PBMC proliferation in MLR, and migration was not significantly influenced by mucosal antigen application.