The infiltration of inflammatory cells, such as mast cells, macrophages, dendritic cells and lymphocytes, was identified in the PAH lung, and an array of inflammatory mediators, including TNFα, IL‐1β, IL‐6, IL‐8, IL‐12, MCP‐1 and RANTES, was abnormally elevated in peripheral blood.2 Here, TNF is linked to pulmonary arterial hypertension.