The depletion of the CXCR3+/CCR4−/CCR6+ (Th1/Th17) together with the observed increased expression of CCL20, the ligand of CCR6, in lungs explanted from patients with IPAH provide some evidence of the recruitment of specific T helper lymphocytes to IPAH lungs [18]. Here, CCR4 is linked to idiopathic pulmonary arterial hypertension.