Lipoteichoic acid suppresses effector T cells induced by Staphylococcus aureus-pulsed dendritic cells

Lipoteichoic acid (LTA), uniquely expressed on gram-positive bacteria, is recognized by Tolllike receptor 2 (TLR2) on not only antigen-presenting cells but also activated T cells. Therefore, it is reasonable to assume that LTA is acting on T cells. However, little is known about the effect of LTA on T-cell regulation. In the present study, we investigated the immunomodulatory effects of LTA on CD4⁺ T cells. Effector CD4⁺ T cells, induced after co-culture with S. aureuspulsed dendritic cells, produced high levels of interferon-γ, CD25, CD69, and TLRs 2 and 4. When effector CD4⁺ T cells were treated with LTA, the expressions of the membrane-bound form of transforming growth factor (TGF)-β and forkhead box P3 increased. Coincidently, the proliferation of effector CD4⁺ T cells was declined after LTA treatment. When TGF-β signaling was blocked by the TGF-β receptor 1 kinase inhibitor, LTA failed to suppress the proliferation of effector CD4⁺ T cells. Therefore, the present results suggest that LTA suppresses the activity of effector CD4⁺ T cells by enhancing TGF-β production.