TNF and pulmonary arterial hypertension: In contrast with inflammatory cytokines TGF-β, MIP-1α, and TNF-α, IL-15 is elevated in animals resistant to SIV-PAH (Fig. 3d, P = 0.01) and is inversely correlated with increased pulmonary pressures at 6 months post-infection (Fig. 3e; left panel, P = 0.0097).