There are also increases of various cytokines and growth factors in certain PAH subtypes, such as IL-1α and IL-6 in connective tissue disease associated PAH (35), platelet-derived growth factor in human immune deficiency virus-associated PAH (36), and tumor necrosis factor-α (TNF-α) and IL-6 in congenital heart disease-associated pulmonary hypertension (PH) (37). Here, TNF is linked to pulmonary arterial hypertension.