We observed that the CD45RA- memory CD4+ T cell fractions of CTEPH patients were less capable of producing TNFα, IFNγ, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 compared with HCs, but intracellular IL-6, IL-10 and IL-17 did not differ between patients and HCs (Figure 4B). Here, IL4 is linked to chronic thromboembolic pulmonary hypertension.