Immunofluorescence techniques for the identification of immune effector cells in rat heart: applications to the study of the myocarditis induced by interleukin-2.

A detailed description is presented of immunohistochemical methods for identification of various types of immune effector cells in rat heart, involving the use of antibodies conjugated with different fluorochromes for the simultaneous demonstration of 2 or 3 different antigens by means of fluorescence microscopy. The initial results of the application of these techniques to the study of the myocarditis induced by interleukin-2 (IL-2) are also presented. Antibodies used included: OX6 antibody (for MHC class II molecules, mainly expressed by dendritic cells): W3/25 and OX8 antibody, for the demonstration of the rat equivalents of CD5 and CD8, respectively: asialo-GM1 ganglioside antibody for the identification of natural killer (NK) cells and lymphokine activated killer (LAK) cells, and ED2 antibody for labeling of macrophages. Fluorochromes used were: fluorescein isothiocyanate (green), tetramethylrhodamine isothiocyanate (red), Texas red sulfonyl chloride (red), and 7-amino-4-methylcoumarin-3-acetic acid (blue). IL-2-induced myocarditis was characterized histologically by infiltration of the myocardium by mononuclear inflammatory cells, microvascular alteration, interstitial edema, and myocyte damage and necrosis. In the initial stages, NK/LAK cells were the predominant type of infiltrating lymphocytes; however, the numbers of these cells decreased sharply in subsequent stages. Macrophages also were initially abundant, and continued to be prevalent throughout the late stages. CD8+ lymphocytes were more numerous than CD4+ lymphocytes. Dendritic-cells showed a diffuse increase in number and also accumulated around foci of myocyte necrosis. Three phenotypes of dendritic cells were recognized, and the possible implications of these findings are discussed. It is hoped that these techniques will prove useful for the immunohistochemical evaluation of various inflammatory diseases of the heart.