Eight preparations of soluble amyloid and degraded amyloid (DAM) were compared immunologically. Unlike amyloid fibrils, six of eight preparations of DAM proved to be relatively strong immunogens. Antisera to DAM reacted weakly or not at all with normal human serum or extracts of normal tissues, but were specifically reactive with amyloid fibrils or DAM.
Comparative studies of DAM'S from eight different subjects showed some degree of cross-reactivity among them, yet demonstrated that they were not identical. Similar conclusions were obtained by quantitative precipitin and complement fixation analyses.
Comparison of the amyloid fibrils with the homologous DAM by complement fixation and absorption studies demonstrated the existence in DAM of antigenic determinants that were lacking or inaccessible in the native fibrils.
A search for amyloid precursors and antibodies to amyloid in the sera of 12 patients proved unsuccessful.