Baseline CD4 cell count between 200 and 499 cells per μL (HR 1·20 [1·01–1·42], p=0·035) or lower than 200 cells per μL (HR 1·32 [1·01–1·74], p=0·044) were significantly associated with incident pulmonary hypertension, but CD4 counts of 500 cells per μL or more were not (HR 1·12 (0·95–1·33), p=0·17; table 2). Here, CD4 is linked to pulmonary arterial hypertension.