Lipoteichoic Acid Suppresses Effector T Cells Induced by <i>Staphylococcus aureus</i>-Pulsed Dendritic Cells

Abstract

Lipoteichoic acid (LTA), uniquely expressed on gram-positive bacteria, is recognized by Toll-like 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. aureus-pulsed dendritic cells, produced high levels of interferon-gamma, 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)-beta and forkhead box P3 increased. Coincidently, the proliferation of effector CD4(+) T cells was declined after LTA treatment. When TGF-beta signaling was blocked by the TGF-beta 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-beta production.