Autoantibodies against platelet-derived growth factor receptor alpha in patients with systemic lupus erythematosus.

Autoantibody against platelet-derived growth factor receptors (PDGFRs) has been reported in scleroderma (SSc). However, it remains unknown whether anti-PDGFRs antibody exists in collagen vascular diseases other than SSc. To answer the question, we developed an ELISA system and examined sera from patients with SLE (n = 75), SSc (n = 31), RA (n = 25) and control individuals. We also reviewed medical records to clarify clinical features of patients with anti-PDGFRα antibody. To examine the functions of anti-PDGFRα antibody in patients, fibroblasts were cultured and stimulated in the presence of purified IgG from patients, and their cell numbers were counted. Anti-PDGFRα antibody was detected in 29% of patients with SLE and in 21% of patients with SSc. Anti-PDGFRα antibody was found in 36% with active SLE, but in 10% in an inactive phase. Immunosuppressive therapy decreased the titer of the antibody. Patients with anti-PDGFRα antibody frequently developed a rash and hematological abnormalities, particular hemolytic anemia. Moreover, anti-PDGFRα antibody in SLE failed to demonstrate agonistic or antagonistic activities on PDGFR signaling. These findings indicate that nonfunctional anti-PDGFRα autoantibody exists in patients with SLE as well as those with scleroderma, and that the antibody could be a marker of disease activity and may be a marker of a subgroup of SLE.