Authors:
Santhakumar Manicassamy , Rajesh Ravindran , Jiusheng Deng , Herold Oluoch , Timothy L Denning , Sudhir Pai Kasturi , Kristen M Rosenthal , Brian D Evavold, & Bali Pulendran
Summary:
Immune sensing of a microbe occurs via multiple receptors. How signals from different receptors are coordinated to yield a specific immune response is poorly understood. We show that two pathogen recognition receptors, Toll-like receptor 2 (TLR2) and dectin-1, recognizing the same microbial stimulus, stimulate distinct innate and adaptive responses. TLR2 signaling induced splenic dendritic cells (DCs) to express the retinoic acid metabolizing enzyme retinaldehyde dehydrogenase type 2 and interleukin-10 (IL-10) and to metabolize vitamin A and stimulate Foxp3+ T regulatory cells (Treg cells). Retinoic acid acted on DCs to induce suppressor of cytokine signaling-3 expression, which suppressed activation of p38 mitogen-activated protein kinase and proinflammatory cytokines. Consistent with this finding, TLR2 signaling induced Treg cells and suppressed IL-23 and T helper type 17 (TH17) and TH1-mediated autoimmune responses in vivo. In contrast, dectin-1 signaling mostly induced IL-23 and proinflammatory cytokines and augmented TH17 and TH1-mediated autoimmune responses in vivo. These data define a new mechanism for the systemic induction of retinoic acid and immune suppression against autoimmunity.
Source:
Nature Medicine; 15, 401-409 (04/01/09)