T-Cell Differentiation Naïve, Precusor T Cells (THP) Recognize Antigens in the Context of HLA Proteins Expressed by Antigen Presenting Cells (APC). Subsequent expression of cytokines orchestrates differentiation into particular effector subclasses (T helper 1, TH1; T helper 2, TH2; T helper 17, TH17; regulatory T, Treg). Each effector subclass is involved in a response to a particular infectious/immune process (shown in parentheses), and each has a cytokine signature (e.g., interferon γ in the case of TH1, IL-4 in the case of TH2, IL-17 in the case of TH17, and TGFβ in the case of Treg) that mediates activity. Tregs control the immune response by repressing the activity of the effectors through several mechanisms including secretion of suppressor molecules and expression of cytokine and chemokine receptors that rob effector cells of essential activation cues. The same transcription factors that integrate the environmental cues for the effector cells are involved in orchestrating the Treg response, thereby ensuring class-specific control of immune-mediated inflammation.