| Abstract: | Rat antibodies to native triple helical calf collagen were used to study the structural requirements of helical antigenic determinants revealed in this particular model. Renaturation of random-coiled chains of collagen in the original proportion of two α1-chains and one α2-chain to triple-helical structures is accompanied by complete recovery of antigenic activity. Although physically similar to native collagen, triple-helical structures prepared from individual chains alone were inactive or exhibited a strongly reduced activity. These results were interpreted as to the involvement of parts of the α1 and α2-chains in several dinstinct helical antigenic determinants of collagen. Further studies with collagenase-derived, triple helical fragments of variable length revealed successive loss of antigenic activity upon reduction in size. However, the smallest fragment, having a length of 78 nm, still contained some of the original antigenic determinants. The antibodies to helical antigenic determinants also showed rather limited interspecies cross-reactions as opposed to the very strong cross-reactions found previously between antigenic determinations of sequential nature in random-coiled α-chains. Helix formation of two different types of α-chains essentially masks these cross-reacting structures. |
