IL4 and pulmonary arterial hypertension: The athymic rat model treated with the SU5416 (VEGF receptor 2 inhibitor used in some animal models to induce pulmonary hypertension) also showed elevated levels of IL-4 in lung tissue extracts, which may enhance the number of mast cells, B cells, and macrophages in perivascular infiltrates, despite the deficiency of T-celIs194.