In line with these results, Koudstaal et al. demonstrated increased plasma levels of IL-6 and C-X-C motif chemokine ligand (CXCL)-9 and CXCL13 in connective tissue disease-associated (CTD)-PAH patients compared to healthy controls (Koudstaal et al., 2021). Here, CXCL9 is linked to pulmonary arterial hypertension.