Identification of a collagen-like antigen different from C1Q component of complement in serum

The problem of the proportions of hydroxyproline proteins in serum linked to collagen and to the C1Q component of complement was examined. The C1Q component from human and bovine serum, and acid soluble calf skin collagen were purified. Antibodies to soluble collagen were prepared. With these antibodies we found by immunoelectrophoresis that in serum two distinct antigens exist: one reacts with antiserum to C1Q and the other reacts with antiserum to collagen. The collagen-like antigen may be precipitated by sodium chloride 4.3 mol/1.