Blum LK, et al. - This investigation was pursued to assess the levels of activated B cells (plasmablasts) in idiopathic pulmonary arterial hypertension (IPAH). Additionally, researchers intended to characterize recombinant antibodies derived from these plasmablasts. An ongoing adaptive autoimmune response, involving IgA plasmablasts that produce anti-endothelial cell autoantibodies in IPAH, was apparent. Triggered by these antibodies, endothelial cell production of cytokines and adhesion molecules resulted, which may contribute to disease pathogenesis. In this work, a role for mucosally-driven autoimmunity and autoimmune injury in the pathogenesis of IPAH was suggested.