To determine the protective effect of Tβ4 in the MCT-treated PAH mouse model, we evaluated the gene expression and protein level of BMPR2, Notch3 and ICAM1 in the lung tissue of WT, Tβ4, WT+MCT and MCT+ Tβ4 groups by real-time PCR and Western blot analysis. The gene discussed is ICAM1; the disease is pulmonary arterial hypertension.