Critical role of IL-21 and T follicular helper cells in hypertension and vascular dysfunction

T and B cells have been implicated in hypertension, but the mechanisms by which they produce a coordinated response is unknown. T follicular helper (Tfh) cells that produce IL-21 promote germinal center (GC) B cell responses, leading to Ig production. Here we investigate the role of IL-21 and Tfh cells in hypertension. In response to angiotensin II–induced (Ang II–induced) hypertension, T cell IL-21 production was increased, and Il21 –/– mice developed blunted hypertension, attenuated vascular end-organ damage, and decreased IL-17A and IFN-γ production. Tfh-like cells and GC B cells accumulated in the aorta, and plasma IgG1 was increased in hypertensive WT but not Il21 –/– mice. Furthermore, Tfh cell–deficient mice developed blunted hypertension and vascular hypertrophy in response to Ang II infusion. Importantly, IL-21 neutralization reduced BP and reversed endothelial dysfunction and vascular inflammation. Moreover, recombinant IL-21 impaired endothelium-dependent relaxation ex vivo and decreased NO production from cultured endothelial cells. Finally, we show in humans that peripheral blood T cell production of IL-21 correlated with systolic BP and IL-17A production. These data suggest that IL-21 may be a novel therapeutic target for the treatment of hypertension and its micro- and macrovascular complications. IL-21 is elevated in hypertensive mice and humans, and plays a critical role in hypertension and vascular dysfunction.