The influence of anti-fibronectin antibodies on interactions involving extracellular matrix components and cells: a possible pathogenic mechanism.

Antibodies, directed to the 30-kD collagen binding domain (CBD) of fibronectin (Fn), have been previously demonstrated in sera from patients with systemic lupus erythematosus (SLE), and we now investigate the possible pathogenic effects of these antibodies on collagen-Fn and cell-Fn interactions. The binding of type 1 collagen to Fn was demonstrated by ELISA, and could be specifically inhibited by the preincubation of solid-phase immobilized Fn with anti-Fn antibodies from SLE sera. By using indirect immunofluorescent staining, anti-Fn antibody containing SLE sera but not normal human serum (NHS) reduced the deposition of newly synthesized collagen and Fn on living human skin fibroblasts. We also found that sera from SLE patients containing anti-Fn antibodies significantly reduced thyroid cell attachment to Fn immobilized on plastic compared with NHS. These effects were shown to be due to the presence of anti-Fn antibodies in these sera, as SLE sera depleted of anti-Fn antibodies did not reduce the deposition of collagen or Fn on cultured fibroblasts, nor did they inhibit cell attachment.