Human tissue fibronectin: expression of different isotypes in the adult and fetal tissues.

The isotype of fibronectin present in human adult and fetal lung tissues was studied by limited proteolysis by cathepsin D followed by immunoblot analysis with domain-specific antibodies. The results indicate that the fibronectin in the adult lung tissue is predominantly the plasma-type whereas the fibronectin in the fetal lung tissue is more related to the cellular-type than to the plasma-type. Thus, it appears that the fibronectin isotype in tissue switches from the cellular-type to the plasma-type during ontogenesis.