The Effects of TLR Activation on T-Cell Development and Differentiation

Figure 1

The effects of TLR on T-cell activation. PAMPs from invading pathogens bind with TLRs expressed in DCs, which causes DC activation. Activated DCs migrate to the draining lymph nodes where, in the presence of co-stimulatory signals and instructing cytokines, they present the antigen epitope with MHC molecules to activate naive T cells. DCs also induce iTreg in the presence of TGF-β and IL-2. These activated T cells move to the site of infection to fight against the invading pathogen. Activation of TLRs in activated T cells induces their survival and clonal expansion. Direct engagement of TLR in iTreg cells promotes their expansion with reduced suppressive function and reprograms them to differentiate into T helper cells, which in turn provide help to effector cells. When the infected pathogen is eliminated, the clearance of TLR ligands results in the suppressive function of the expanded iTreg cells being restored. This serves to regulate the expanded effector T-cell population.