T-helper cells as new players in ANCA-associated vasculitides

In anti-neutrophil cytoplasmic autoantibody-associated vasculitides (AAV), several observations support a key role of T-helper cells (CD4(+) T cells) in disease pathophysiology. An expanded population of effector memory CD4(+) T cells in AAV patients may contribute to tissue injury and disease progression. In addition, functional impairment of regulatory T cells (T-Regs) is reported in AAV patients. A fraction of T-Regs have the capacity to differentiate into Th17 cells in the context of a proinflammatory environment. Therefore, nonfunctionality of T-Regs described in AAV patients may be caused by their conversion into IL-17-producing cells that may contribute to granulomatous vasculitis. Further investigations directed at the plasticity of T-Regs in AAV patients are warranted.