IL6 and pulmonary arterial hypertension: Immune system dysregulation is reported to play a pivotal role in the pathogenesis and progression of PAH due to actively recruiting inflammatory cells and irreversibly remodeling the pulmonary vasculature, followed by overproduction of pro-inflammatory cytokines, including IL-1β, IL-18, IL-6, IL-18, and TNF-α.[4,8] PAH is the result of dysfunctional interaction between the immune system and the pulmonary endothelium.