Our results demonstrate that (1) there is a systemic increase in soluble activation markers of different leucocyte subsets, in particular those reflecting monocyte and T-cell activation, in precapillary PH with mainly high levels in APAH (2) the monocyte/macrophage marker sCD163 was independently associated with poor long-term prognosis in the group as a whole (3) the T cell marker sCD25 was associated with poor prognosis in APAH, while sCD163 and the neutrophil marker NGAL were associated with poor prognosis in IPAH and CTEPH. The gene discussed is CD163; the disease is idiopathic pulmonary arterial hypertension.