Tropocollagen preparations from carp, buffalo fish, rats, calves, sheep, and humans have been studied by electron microscopy and serologic methods. Tropocollagens from each species appeared identical by electron microscopy but they were readily distinguished (except between sheep and calves) by C'-fixation tests with rabbit antisera against the various tropocollagens. Tests with calf tropocollagen antiserum showed no distinction between tropocollagen isolated from different tissues nor between individuals of the same or different strains.
The major immunogenic sites in native tropocollagen are the telopeptides, and these are present on both α1- and α2-chains. The C'-fixing activity was lost with heat denaturation of the tropocollagen, but could be recovered in a concentration-dependent process on cooling.
The fact that pure and enzyme-treated collagen can provoke serologic reaction implies that collagenous sutures and prostheses used in surgery may lead to sensitization and rejection, a fact which may merit clinical concern.