Cell staining with direct and indirect assay formats

The fundamental concept of immunohistology is the localization of antigens within tissue sections by means of specific antibodies where the antigen-antibody reaction is detected with a histochemical color reaction visible in the light microscope or with fluorochromes by UV light in a fluorescence microscope. The principle of immunohistology is ascribed to A H COONS, the inventor of the immunofluorescent technique (COONS AH et al., 1941; COONS AH et al., 1942; COONS AH and KAPLAN MH, 1950; COONS AH et al., 1951; COONS AH, 1954; COONS AH et al., 1955; COONS AH, 1958). His original intent was the identification of putative foreign antigens in affected tissues in certain diseases, and soon it became evident that this technique would be of great potential for the detection of all types of antigens in cells. Even if the great impact of this technique on laboratories of experimental cell research, tumor and molecular biology was realized from the very beginning, methods of immunofluorescence were used for a long time only by few specialized research laboratories. Some of the reasons were lack of skill in the preparation of reliable reagents and, more importantly, lack of acceptance by the pathologists.