Small intestinal CD103+ dendritic cells display unique functional properties that are conserved between mice and humans.

A functionally distinct subset of CD103(+) dendritic cells (DCs) has recently been identified in murine mesenteric lymph nodes (MLN) that induces enhanced FoxP3(+) T cell differentiation, retinoic acid receptor signaling, and gut-homing receptor (CCR9 and alpha4beta7) expression in responding T cells. We show that this function is specific to small intestinal lamina propria (SI-LP) and MLN CD103(+) DCs. CD103(+) SI-LP DCs appeared to derive from circulating DC precursors that continually seed the SI-LP. BrdU pulse-chase experiments suggested that most CD103(+) DCs do not derive from a CD103(-) SI-LP DC intermediate. The majority of CD103(+) MLN DCs appear to represent a tissue-derived migratory population that plays a central role in presenting orally derived soluble antigen to CD8(+) and CD4(+) T cells. In contrast, most CD103(-) MLN DCs appear to derive from blood precursors, and these cells could proliferate within the MLN and present systemic soluble antigen. Critically, CD103(+) DCs with similar phenotype and functional properties were present in human MLN, and their selective ability to induce CCR9 was maintained by CD103(+) MLN DCs isolated from SB Crohn's patients. Thus, small intestinal CD103(+) DCs represent a potential novel target for regulating human intestinal inflammatory responses.