The effects of preliminary proteolysis on the immunohistochemical and dye staining properties of elastic fibres.

Antibodies to alpha-elastin peptides, amyloid P component, lysozyme and plasma protease inhibitors have been used in an immunoperoxidase method to stain elastic fibres in frozen sections of human breast tissues. A loss of immunoreactivity seen in formalin-fixed, paraffin-embedded sections was reversed by a preliminary proteolysis. Differences in the tinctorial dye and immunohistochemical staining patterns following proteolysis by a variety of enzymes suggests a selective unmasking or removal of elastic fibre components and thus the presence of separate binding sites for individual antibodies and tinctorial dyes. Antibody blocking experiments and double immunoenzymatic labelling support the existence of several different epitopes within elastic fibres.