Figure 1.

Layers of regulation of the immune response. At low levels of inflammation (A) both Foxp3⁺ naturally occurring Tregs and Foxp3^– IL-10 Tregs inhibit CD4⁺ T cell proliferation through IL-10–independent, cell contact–dependent mechanisms. (B) Similar mechanisms may control immune responses to self antigens and autoimmune pathologies associated with low-level inflammation such as gastritis. (C) When strong inflammation occurs, with activation of APCs, effector molecules, such as IL-10 and TGF-β, secreted by Tregs are required to control CD4⁺ T cell responses. TLR, Toll-like receptor.