Conversely, PAH displayed a negative association with the count of CD33+ HLA DR+ CD14dim immune cells (β: -0.04, IVW p: 0.027) that was related to cerebral white matter volume change rate (β: -45.24, IVW p: 0.022) with a significant mediation effect (1.74, confidence interval: 0.01 to 4.39). Here, CD33 is linked to pulmonary arterial hypertension.