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Tissue slices (500 to 1000 microns thick) of archival formalin-fixed, paraffin-embedded breast tissue were immunostained by a cytokeratin antibody (MNF116) using a streptavidin-biotin complex procedure. The technique requires prolonged exposure of tissue slices to the reagents. Use of the detergent Triton X-100 facilitated penetration of high molecular weight reagents through the tissue slices. Fifty of 58 slices 500 microns thick (86%) showed good to excellent immunostaining, and 13 of 20 slices 1000 microns thick (65%) showed similar staining. Omission of the primary antibody eliminated any immunostaining. Comparison with corresponding Haematoxylin staining of the thick slices (the conventional procedure for such breast tissue slices) showed that thick-slice cytokeratin immunostaining markedly improved visualization of the epithelial structure in normal lobules and invasive carcinomas. Although the immunohistochemical technique takes 33 days for completion, the quality of the epithelial images outweighs this disadvantage.

Tissue slices (500 to 1000 microns thick) of archival formalin-fixed, paraffin-embedded breast tissue were immunostained by a cytokeratin antibody (MNF116) using a streptavidin-biotin complex procedure. The technique requires prolonged exposure of tissue slices to the reagents. Use of the detergent Triton X-100 facilitated penetration of high molecular weight reagents through the tissue slices. Fifty of 58 slices 500 microns thick (86%) showed good to excellent immunostaining, and 13 of 20 slices 1000 microns thick (65%) showed similar staining. Omission of the primary antibody eliminated any immunostaining. Comparison with corresponding Haematoxylin staining of the thick slices (the conventional procedure for such breast tissue slices) showed that thick-slice cytokeratin immunostaining markedly improved visualization of the epithelial structure in normal lobules and invasive carcinomas. Although the immunohistochemical technique takes 33 days for completion, the quality of the epithelial images outweighs this disadvantage.

A panel of peroxidase-conjugated lectins was used to stain frozen sections of human foetal, neonatal, infant and adult aortae. Two main distinctive staining patterns were observed at the light microscope level, depending on the lectin employed. Lectins from Concanavalin A, Triticum vulgaris, Arachis hypogaea and Glycine max resulted in staining of the surfaces of aortic elastic lamellae and the interlamellar areas. With lectins from Dolichos biflorus and Bandeiraea simplicifolia staining was seen predominantly in the interlamellar areas. The findings indicate the presence of several different glycoconjugates at various sites within the aorta. In addition, there were alterations in the lectin binding affinities of the aortae that were dependent upon age. The findings are interpreted as indicating sequential changes in the composition of glycoprotein or proteoglycan moieties in the development of the human aorta.

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.

Congo Red is an acid-base indicator dye. In free solution the colour and absorption characteristics of Congo Red depend not only on the pH but are also governed by the nature of the solvent environment. In tissue sections stained by Congo Red, alteration of the pH and the use of non-aqueous solvents can effect differential colouring of the tissue components. Stained sections of unmodified and chemically substituted celluloses show that differential red or blue coloration reflects the acidic or basic character of the substrate. In stained tissue sections, secondary protein structure and porosity of the substrate may also influence their colour. The effect of non-aqueous solvents is probably to modify the ionization state of the dye- substrate complex, thus altering the colour of the Congo Red. Such solvents may also change the aggregation or solvation states of the dye, with consequent modification in the colour of tissue components.