Really old-palaeoimmunology: immunohistochemical analysis of extracellular matrix proteins in historic and pre-historic material.

In this review, we summarize data concerning the respective preservation and deterioration of antigenic determinants of various collagenous and non-collagenous extracellular matrix (ECM) proteins in palaeontologic material of different ages. ECM proteins are the major quantitative constituents of mammalian organisms and were, therefore, selected as important representative proteins for these analyses. The specimens, studied by immunofluorescence and immunohistochemical techniques, included the skin of 500-1500 year-old human mummies from Peru, skin and striated muscle from the 5300-year-old glacier mummy ("Iceman") from Tyrol, Austria, and a 50-million-year-old bat with preserved soft body parts from the fossil excavation site of Messel, Germany. In frozen sections of the former two sources, epitopes recognized by specific antibodies for triple-helical antigenic determinants of different types of collagen resistant against conventional proteases were preserved, while non-helical domains, as well as the non-collagenous ECM proteins, could no longer be demonstrated. The fossil bat, although showing evidence of fibrous, collagen-like structures in conventional histology, revealed no collagenous or non-collagenous ECM proteins by any technique. It later turned out that this was due to the replacement of the original soft parts in these fossils by lawns of bacteria. These studies introduced immunological techniques into palaeontology and opened new approaches for studying physiologically- and pathologically-altered structures in tissues of animals and humans of considerable historical age.