Figure 2.

Signals from DCs can influence the differentiation of naïve T cells. Stimulated, mature DCs present not only antigen in the context of MHC but also costimulatory surface molecules necessary for T cell activation. Furthermore, the type and quantity of cytokines secreted by DCs in conjunction with these costimulatory molecules can direct the naïve T cell into different effectors phenotypes. IL-12 secretion from the DC initiates a Th1 type response characterized by secretion of IFNγ. IL-4 secretion from the DC results in a Th2 type response characterized by the secretion of IL-4, IL-5, and IL-10. The cytokines secreted by DCs are induced following ligation of cellular receptors (PRRs or TLRs) and signals from the surrounding tissues (i.e., IL-8). New evidence is emerging regarding the role of DCs in activating Th17 and Treg cells.