T Cells and Their Subsets in Autoimmunity

Upon encounter with antigen and depending on the cytokine milieu, T helper (Th) cells can differentiate into various effector T cell subsets, including the well-defined Th1 and Th2 subsets as well as the more recently discovered Th17, Th9, and follicular T helper (TFH) subsets. Among these, self-reactive Th1 and Th17 cells have been associated with organ-specific autoimmunity, while self-reactive TFH cells have been shown to promote aberrant B cell responses in systemic autoimmune diseases. On the other hand, regulatory T cell subsets including Foxp3+ regulatory T cells (Tregs) and type 1 regulatory T cells (Tr1) can regulate autoimmunity by suppressing effector T cell responses. Here, we give an overview of the different Th cell subsets, their development, and how the interplay between them can promote or inhibit autoimmune tissue inflammation.