IL6 and pulmonary arterial hypertension: Numerous studies have documented increased levels of IL-6 in PAH patients (Humbert et al., 1995; Selimovic et al., 2009; Soon et al., 2010; Duncan et al., 2012; Cracowski et al., 2014; Heresi et al., 2014; Matura et al., 2015; Al-Naamani et al., 2016; Prins et al., 2017).