IL4 and pulmonary arterial hypertension: Similarly, in pulmonary arterial hypertension (PAH) as well as SARS-CoV, both arms of the inflammatory system (namely IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12 and TNF-α) have been shown to be upregulated [108,109,110], suggesting a common systemic pathway of activation in welding syndrome, ARDS, PAH and SARS-CoV infections.