Figure 1.

The balance between Treg loss (red arrows) and Treg renewal (green arrows). Resting Tregs can be activated by recognizing a specific ergotope presented in either of 2 ways: by an activated effector T cell or by a professional APC (yellow cell). The interaction between the activated Treg (green cells) and the activated effector T cell (purple cells) leads to inactivation of the effector T cell but also to anergy of the Treg (white cells). Thus, presentation of ergotopes by activated T cells leads to Treg loss. In contrast, an ergotope presented by a professional APC activates Treg proliferation and cycling (Treg renewal).