Implication of B lymphocytes in the pathogenesis of ANCA-associated vasculitides.

ANCA-associated vasculitis (AAV) is a subgroup of vasculitides characterized by the detection of anti-neutrophil cytoplasm antibodies (ANCA). Until recently, the pathogenesis of AAV mainly involved neutrophils, T cells, and ANCA. Importantly, data were recently published supporting B-cell implication in this setting. Thus, the identification of activated B lymphocytes in granulomatous lesions and the efficacy of B-cell depletion using rituximab in the treatment of patients with AAV changed our mind. However, the impact of B lymphocytes on disease activity and its specific role in the pathogenesis of AAV remains unclear, at least in part as the consequence of the limited number of patients investigated and the restricted number of studies investigating B-cell subsets. Perturbations of B-cell homeostasis have been identified in AAV with increased expression of CD38 and decreased expression of CD5 in active phase, contrasting with increased expression of CD25 and CD86 in remission state. Although decreased secretion of interleukin (IL)-10 has also been reported during disease flares, these data remain controversial and the cytokines secretion profile of B-cells needs to be further investigated. Herein, we summarize recent advances in the understanding of the implications of B-cells in the field of AAV and propose new fields of investigation for a better understanding of B lymphocytes in the pathogenesis of AAV.