Elevated levels of chemokines such as Regulated upon Activation, Normal T Cell Expressed and Presumably Secreted (Dorfmüller et al., 2002), fractalkine (CX3CL1) (Perros, Dorfmüller, Souza, Durand‐Gasselin, Godot, et al., 2007), CC chemokine ligand 2 (CCL2) (Sanchez et al., 2007), and CXCL10 (Ross et al., 2012) are also found in patients with PAH. Here, CX3CL1 is linked to pulmonary arterial hypertension.