Primary pulmonary hypertension, tissue plasminogen activator antibodies, and HLA-DQ7

Antibodies to fibrin-bound tissue plasminogen activator (tPA) have been found in autoimmune diseases with vascular injury, such as systemic lupus erythematosus and scleroderma. The purpose of this study was to determine whether patients with primary pulmonary hypertension (PPH) have an immunogenetically determined response to fibrin-bound tPA. Antibodies to fibrin-bound tPA were determined in three patient groups: 45 adults with PPH, 41 children with PPH, and 40 children with anatomically large congenital pulmonary to systemic communications (PHT+shunt). The frequencies of the HLA class II (DRB1,3,4,5, and -DQB1) alleles in these three patient groups were compared with those of 51 healthy Caucasian control subjects. Fibrin-bound tPA antibodies were found in four of 45 (9%) adults with PPH, four of 41 (10%) children with PPH, and one of 40 (2.5%) children with PHT-shunt. HLA class II typing, which was available for seven of nine Caucasians with fibrin-bound tPA antibodies, revealed that six of seven (86%) patients typed HLA-DQ7 (DQB1*0301) and one typed HLA-DQ6. The 86% frequency of HLA-DQ7 in the antibody positive patients was significant compared with the 29% frequency in the healthy control subjects (p = 0.007, p corrected [pc] = 0.05, OR = 14.4). Of interest, these antibody-positive patients, although lacking antiphospholipid antibodies, shared an amino acid epitope, common to HLA-DQB1*06,07 and 08 subtypes, which was previously reported to be associated with the lupus anticoagulant. In conclusion, antibodies to fibrin-bound tPA and HLA-DQ7, and possibly the same epitope associated with the lupus anticoagulant, defined a small subset of children and adults with PPH.