Interestingly, the expression of BAFFR, TNFSF4, TNFRSF4, MZB1, CD19, IGHM, and JCHAIN was elevated in the present study, indicating that B cells were activated to produce antibodies, thus in line with the evidence of local immunoglobulin production in PAH (38). Here, IGHM is linked to pulmonary arterial hypertension.