IMMUNOLOGICAL CHARACTERIZATION OF MEMBRANE-BOUND COLLAGEN IN NORMAL HUMAN FIBROBLASTS - IDENTIFICATION OF A DISTINCT MEMBRANE COLLAGEN

Collagen, the major extracellular matrix protein, is also a membrane protein. Two types of collagen are detected on the normal human fibroblast membrane in culture, type I collagen and a new immunologically and chemically distinct collagen, type M (membrane) collagen. Antibodies [rabbit] to type M collagen elicited complement-mediated cytotoxicity, which could be blocked by pretreatment of the cells with bacterial collagenase or the antibody with type M collagen. Pretreatment of the cells with other proteolytic enzymes or the antibody with type I collagen or type III collagen had no effect on this complement-mediated cytotoxicity. Although type I collagen is the major collagen synthesized by normal human fibroblasts, type M collagen may be the major cell membrane collagen and may be a major cell membrane component. [The relevance of these results to immunopathological connective tissue disease is discussed.].