Endothelial cell (EC) apoptosis seems to play an important role in the pathophysiology of
pulmonary arterial hypertension (PAH). We aimed to test the hypothesis that circulating anti-endothelial cell
antibodies (
AECA) of PAH patients induce EC apoptosis.
Immunoglobulin (Ig)G was purified from sera of PAH patients (n = 26), patients with
systemic lupus erythematosus (SLE)
nephritis without PAH (n = 16), patients with
systemic sclerosis (SSc) without PAH (n = 58) and healthy controls (n = 14). Human umbilical vein endothelial cells (HUVECs) were incubated with patient or healthy control
IgG for 24 h. Thereafter, apoptosis was quantified by
annexin A5 binding and hypoploid cell enumeration by flow cytometry. Furthermore, real-time cell electronic sensing (RT-CES™) technology was used to monitor the effects of purified
IgG from patient and healthy control
IgG on HUVECs. As demonstrated previously,
IgG of
AECA-positive SLE
nephritis patients (n = 7) induced a higher percentage of apoptosis of HUVECs compared to
IgG of
AECA-negative SLE
nephritis patients and healthy controls. Furthermore,
IgG of
AECA-positive SLE
nephritis patients induced a marked decrease in cell index as assessed by RT-CES™ technology.
IgG of
AECA-positive PAH patients (n = 12) and SSc patients (n = 13) did not alter the percentage of HUVEC apoptosis or cell index compared to
IgG of
AECA-negative PAH and SSc patients and healthy controls.
AECA-positive PAH patients, in contrast to SLE
nephritis patients, do not have circulating
IgG AECA that enhances apoptosis of HUVECs in vitro. Further studies should focus on other mechanisms by which
AECA may enhance EC apoptosis in PAH, such as antibody-dependent cell-mediated cytotoxicity.