MECHANISM FOR ANTIGEN-DETECTION ON DEPLASTICIZED EPOXY SECTIONS

The purpose of this investigation was to explain why deplasticizing of epoxy sections gives higher immunogold labeling than non-deplasticizi ng. The methods used were the following: (1) Comparison of the ratio o f immunogold labeling of deplasticized and non-deplasticized sections with gold particles of different sizes and comparison of this ratio wi th respect to sections of different thickness, (2) the tilt method (Br orson et al., 1994). Human kidney tissue with amyloid A depositions, h uman fibrin, and human pituitary tissue were embedded, sections were d eplasticized on grids, treated with anti-Aa, anti-fibrinogen or anti-A CTH (ACTH=adrenocorticotropic hormone), and reembedded on grids. Indic ations of significant antibody penetration were found only at the peri phery of structures (ACTH-vesicles). This penetration was about 30 mn. The ratios of immunogold labeling of deplasticized and non-deplastici zed sections were approximately 2, 5 and 1 for amyloid, fibrin and ACT H, respectively, and were independent of the gold particle size. No si gnificant differences of gold labeling were found between thicker and thinner deplasticized epoxy sections regardless the gold particle size . No significant differences of gold labeling between deplasticized ep oxy sections and LR-White sections were found on interior areas of ACT H-vesicles or amyloid A plaques. The increased labeling of deplasticiz ed epoxy sections compared to normal epoxy sections seemed to be mainl y a surface phenomenon. The practical significance of this observation is that deplasticizing of epoxy sections may be a better method for l ocalizing antigens at the periphery of structures than the use of othe r resin embedding media. Deplasticizing of epoxy sections may be a met hod of choice in a pathological laboratory to detect antigens in routi nely embedded tissues.