The role of T helper subsets in autoimmunity and allergy

The classification of T helper (TH) cells in subsets has progressively expanded and more effector subsets, besides TH1 and TH2, have been documented. These include follicular helper T cells (TFH), and the more recent TH17, ‘TH9’, and ‘TH22’. In addition, TH are no longer thought of as terminally committed effector cells, with plasticity now recognized. Identification of the molecular mechanisms that drive differentiation of TH cells has established a link between environmental factors and TH subsets, with regard to both the initiation and severity of immune disorders. The role of TH in autoimmune-disorders and allergic-disorders is now re-evaluated, with current data suggesting a central role for TH17 in orchestrating adaptive-immune responses, while TFH are instrumental in coordinating B cell immunity.