We studied in what way different species of lactobacilli prime human DCs for their ability to drive Treg cells.
Human monocyte-derived DCs were cultured in vitro with lactobacilli of different species.
Two different species of lactobacilli, Lactobacillus reuteri and Lactobacillus casei, but not Lactobacillus plantarum, prime monocyte-derived DCs to drive the development of Treg cells. These Treg cells produced increased levels of IL-10 and were capable of inhibiting the proliferation of bystander T cells in an IL-10–dependent fashion. Strikingly, both L reuteri and L casei, but not L plantarum, bind the C-type lectin DC-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN). Blocking antibodies to DC-SIGN inhibited the induction of the Treg cells by these probiotic bacteria, stressing that ligation of DC-SIGN can actively prime DCs to induce Treg cells.
The targeting of DC-SIGN by certain probiotic bacteria might explain their beneficial effect in the treatment of a number of inflammatory diseases, including atopic dermatitis and Crohn's disease.