Autoimmunity Is a Significant Feature of Idiopathic Pulmonary Arterial Hypertension

Background: Autoimmunity may play a role in idiopathic pulmonary arterial hypertension (IPAH). It is not clear if this is causative, or as a bystander of disease and if it carries any prognostic or treatment significance. Methods: Comprehensive immune phenotyping was performed in IPAH patients, utilising patient samples from the UK National cohort study of Idiopathic and Heritable PAH. Standardised flow cytometric analysis of peripheral blood mononuclear cell types was assessed in IPAH patients and healthy controls. Serum autoantibody biomarkers were assayed using a Protoplex™ autoimmune panel in 473 type I PAH patients and 946 matched controls. Finally, a GST-fusion human proteomic screen was undertaken to identify novel circulating autoantibodies in PAH, and 350 PAH sera samples ELISA assayed for a putative antibody to BMPR2. Findings: Flow cytometric immune profiling demonstrates IPAH is associated with a signature consistent with altered humoral immune response. Increased autoantibody positivity was detected in PAH and patient subgroups associated with worse haemodynamic parameters but better overall survival. We identify a small subset of PAH patients who demonstrate immunoglobulin reactivity to the extracellular domain of the TGFbeta superfamily receptor, BMPR2, a protein which is strongly associated with hereditary causes of the disease. Interpretation: This evidence strongly suggests a proportion of patients with IPAH have an autoimmune component to the disease and that the BMPR2 pathway may be a target. Future trials targeting inflammation need to consider biomarker stratification. Funding Information: NIHR BRC, The Dinosaur Trust, MRC (MC_UU_00002/4) and the Wellcome Trust [WT107881]. Declarations of Interest: Gerry Coghlan reports grants and personal fees for conference attendance from Johnson & Johnson, personal fees for lectures from GlaxoSmithKline, Bayer and MSD, outside the submitted work. Paul Corris reports grants and personal fees for lectures and consultations from Actelion and Bayer, and personal fees for lectures and consultations from MSD, outside the submitted work. Luke Howard reports grants, personal fees for lectures, steering committee and advisory board work, and non-financial support for meeting attendance from Actelion, personal fees for lectures and advisory board work from Bayer and MSD, personal fees for advisory board work from GSK, outside the submitted work. Martin Johnson reports grants and personal fees for meeting attendance, lectures, and advisory board work from Actelion and MSD, outside the submitted work. David Kiely reports grants, personal fees, and other support from Actelion, Bayer and GSK, and personal fees and other support from MSD, outside the submitted work. Allan Lawrie reports grants from British Heart Foundation and Medical Research Council, grants, personal fees, and travel support from Actelion Pharmaceuticals Ltd, grants and personal fees from GlaxoSmithKline, outside the submitted work. James Lordan has received modest honoraria from Actelion and modest support to attend conference from Merck Sharp & Dohme, outside the submitted work. Joanna Pepke Zaba received fees for research grant, support to travel to meetings and honoraria from Actelion, Bayer, GlaxoSmithKline and Merck Sharp & Dohme, outside the submitted work. S.John Wort has received modest honoraria from GlaxoSmithKline, Actelion and Bayer and has received significant research grants from Actelion and Bayer, outside the submitted work. Nicholas Morrell reports personal fees from GSK and Johnson & Johnson/Actelion, outside the submitted work. Mark Toshner reports personal fees from GSK, grants and personal fees from J&J/Actelion, grants from Merck and Bayer, outside the submitted work. All other authors have nothing to disclose Ethics Approval Statement: Ethical approval was obtained, and informed written consent was given. For collection and processing of samples for autoantibody analysis, including controls ethical approval was obtained (An integrated approach to dissect the determinants, risk factors and pathways of ageing in the immune system 15/EE/0327, IRAS # 188383 and Genetics and epidemiology of aging-associated conditions in the Sardinian population, ProgeNIA PROT 2171/CE).