Toll-like receptor 2–dependent induction of vitamin A–metabolizing enzymes in dendritic cells promotes T regulatory responses and inhibits autoimmunity

S Manicassamy, R Ravindran, J Deng, H Oluoch… - Nature medicine, 2009 - nature.com
S Manicassamy, R Ravindran, J Deng, H Oluoch, TL Denning, SP Kasturi, KM Rosenthal…
Nature medicine, 2009nature.com
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 …
Abstract
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.
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