Specificity of the antibody response in inbred mice to bovine type I and type II collagen.

Mouse antibodies to soluble bovine skin (type I) collagen react with determinants which are located in the rigid triple-helical portion of the antigen and become destroyed upon unfolding the molecule. Helical antigenic determinants are dependent on the genuine chain assembly, e.g. alpha[1(I)]2alpha2. Artefactual triplehelical structures of the composition [alpha1(I)]3 or [alpha2]3 or a genetically distinct type II collagen from cartilage showed no or only weak cross-reactivity. Pepsin treatment of type I collagen known to remove short, non-helical sequences at both ends of the molecule had virtually no effect on antigenicity and immunogenic activity. A radioimmunoassay failed to detect antibodies in three congenic resistant mouse strains immunized with denatured type I collagen. These strains had been previously classified as high or low responders to native type I collagen. Agglutination titres vs denatured collagen culd already be demonstrated in nonimmune sera. The agglutinating activity was labile against heating at 56 degrees and could not be increased by immunization. Two out of five inbred strains showed a high response against pepsin-dissolved bovine type II collagen with the chain composition [alpha1(II)]3. Lack of correlation in the responder state to both collagen types indicated control by different immune response genes. Antibodies to type II collagen also reacted against triple-helical antigenic determinants and showed neglible cross-reaction with type I collagen.