TNF and pulmonary arterial hypertension: Patients with PAH showed an increase in several serum cytokines such as Interleukin 1β, Interleukin 2, Interleukin 4, Interleukin 5, Interleukin 6, Interleukin 8, Tumor Necrosis Factor α (TNFα), and Interferon (IFN), and these levels had a previously unrecognized impact in patient survival (33).