Immunological characterization of the 7-S domain of type IV collagens

Antisera were raised against the long and short form of mouse and human 7-S collagen and against type IV collagens solubilized by acid extraction or limited digestion with pepsin. All the antisera showed strong binding for 7-S collagen in radioimmunoassays demonstrating that the 7-S domain which serves as a cross-linking region of type IV collagen is the most immunogenic portion of the molecule. Cross-reaction studies and analysis of fragments showed a complex antigenic structure including some determinants common to the long and short form of 7-S collagen and others unique for the long form. Purified antibodies against 7-S collagen reacted in indirect immunofluorescence with almost all basement membranes of the body indicating that the 7-S domain is a common structural element of type IV collagens.