Fibronectin: its relationship to basement membranes. I. Light microscopic studies.

Fibronectin is a large molecular weight glycoprotein which has been shown to be associated with cell surfaces, extracellular fluids, and connective tissues. Its possible relationship with basement membranes remains controversial. To define this relationship, the distribution of this antigen was evaluated by light microscopic immunoperoxidase techniques in kidney, skin, skeletal muscle, gastrointestinal tract and parietal yolk sac carcinoma. In addition, antibodies against basement membrane and interstitial collagen were used as controls of the specificity of this reaction. Any possible cross-reactivity between plasma fibronectin and basement membrane was examined by immunodiffusion, immunoelectrophoresis and ELISA techniques. The results indicate that antibodies to plasma fibronectin do not co-localize with antibodies to basement membrane constituents. Furthermore, by immunodiffusion or ELISA, there was no cross-reactivity between plasma fibronectin and anti-basement membrane antibody, nor between basement membrane and anti-plasma fibronectin antibody. We conclude that fibronectin is probably not part of the basement membranes studied.