The MR analysis findings indicated a positive genetic causal link between PAH and 5 immune cells (OR > 1, P < .05), specifically involving CD11b on basophil, CD20-CD38-AC, CD4 Treg AC, FSC-A on T cell, Native DN(CD4-CD8-)%T cell. The gene discussed is CD8A; the disease is pulmonary arterial hypertension.