Immunohistochemical analysis of murine CD95/Fas/Apo-1 receptor and its ultrastructural distribution in the thymus

CD95/Fas/Apo-1 is a cell surface receptor that, upon contact with its ligand, induces cells to die by apoptosis. In view of the importance of Fas receptor (FasR) in immunologic tolerance, an immunohistochemical analysis of FasR expression was performed in the lymphoid and certain parenchymal tissues of normal and mutant MRL/lpr mice using a rabbit polyclonal anti-Fas receptor antibody. FasR was expressed by immunoperoxidase (IP) in the cortex and at the corticomedullary junction of the thymus of normal mice. By immunoelectron microscopy FasR was detected on the cell membrane of normal thymocytes. In MRL/lpr mice, FasR protein expression could not be clearly detected. FasR protein expression was not detected in the heart, liver or ovary by IP, presumably reflecting the low number of receptors in these tissues.