Monoclonal antibodies that distinguish between human cellular and plasma fibronectin

Two monoclonal antibodies have been developed against human fibronectin expressed by simian virus 40 transformed human mammary epithelial cells. Monoclonal antibody ICRF-FN-3 recognizes a determinant on human cellular but not plasma fibronectin. The antigenic site recognized by FN-3 is lost after limited proteolysis of cellular fibronectin with alpha-chymotrypsin but not trypsin. Monoclonal antibody, ICRF-FN-4, against a determinant on both human plasma and cellular fibronectin reacts with an antigenic site on fibronectin which is not destroyed by trypsin or alpha-chymotrypsin. Although the epitopes recognized by FN-3 and FN-4 are expressed similarly by cells from the human breast they are expressed differently on rat mammary (RAMA) cell lines.