Langerin-expressing dendritic cells in gut-associated lymphoid tissues

Dendritic cells (DCs) are key regulators of the immune system. They act as professional antigen-presenting cells and are capable of activating naive T cells and stimulating the growth and differentiation of B cells. According to their molecular expression, DCs can be divided into several subsets with different functions. We focus on DC subsets expressing langerin, a C-type lectin. Langerin expression is predominant in skin DCs, but langerin-expressing DCs also exist in mucosal tissue and can be induced by immunization and sometimes by nutrient deficiency. Topical transcutaneous immunization induces langerin+CD8 alpha- DCs in mesenteric lymph nodes (MLNs), which mediate the production of antigen-specific immunoglobulin A antibody in the intestine. Yet, in one recent study, langerin+ DCs were generated in gut-associated lymphoid tissue and contributed to the suppressive intestinal immune environment in the absence of retinoic acid. In this review, we focus on the phenotypic and functional characteristics of langerin+ DCs in the mucosal tissues, especially MLNs.