Immunohistochemical demonstration of plasma protein in squamous epithelium of formalin-fixed, paraffin-embedded oral mucosa.

The distribution of immunoglobulins and fibrinogen in normal and inflamed oral mucosa was examined by direct immunofluorescence using enzyme-treated sections of formalin-fixed, paraffin-embedded tissue. Plasma proteins were found inter- and intracellularly in the surface epithelium in most of the normal and all of the inflamed mucosal specimens. This diffusion of plasma proteins into the surface epithelium was shown to contribute to the appearance of edematous epithelial cells and eosinophilic bodies ("keratin pools"). The results clearly demonstrate that oral epithelium is not to be regarded as a covering membrane isolated from the underlying connective tissue. Furthermore, the study confirms that immunohistochemical studies can be performed on enzyme-pretreated sections of routinely fixed and embedded tissue although it is emphasized that the method is not of universal applicability.