IL15 and pulmonary arterial hypertension: The defect in IL-15 signaling exacerbates PAH and contributes to RV remodeling, including capillary reduction and hypertrophy in hypoxia-PH and MCT-induced PAH (MCT-PAH) rats.55 The role of IL-6/STAT3 signaling in promoting PAH through stimulation of PASMC proliferation has been established in patients, animal models, and cellular studies.