Submikroskopische und enzymhistochemische Beitr�ge zur formalen Genese des Epitheloidzellgranuloms

Granulomatous pulmonary reactions after instillation of Mycobacterium gordonae. Light and electron microscopic investigations on the rat model

Pathogenicity of Mycobacterium gordonae in humans has so far been reported in the literature in the form of case reports only. Systematic experimental investigations have not been published. For this reason, the pathogenicity of two Mycobacterium gordonae strains isolated from human ivestigation material were tested in animal experiments. Measured amounts of in some cases live and in some cases heat-killed M. gordonae were instilled into the right lower lobe of the lung of anesthetized Wistar rats by means of a polyvinyl catheter. The tissue changes were investigated at graduated time intervals between 1 h and 24 weeks by light and electron microscopy. Small granulomas consisting of leukocytes and macrophages develop in the lung tissue 3 days after the instillation. Under the electron microscope, intracellular mycobacteria can be demonstrated. These do not proliferate. After 2 weeks, sarcoid granulomas have formed from epitheloid and giant cells. Casefying necroses are absent. Electron microscopically, it can be shown that the mycobacteria are broken down intracellularly in phagolysosomes, so that sarcoid granulomas free of bacteria are left behind.

Characterization of cells involved in the formation of granuloma. An ultrastructural study on macrophages, epitheloid cells, and giant cells in experimental tubulo-interstitial nephritis

In experimental tubulo-interstitial (anti-basement membrane) nephritis of the rat, granulomatous inflammation develops around immunologically altered tubular basement membranes. The present light- and electron microscopic studies indicate that in the course of the granulomatous reaction, tissue monocytes evolve from blood monocytes and pursue two independent pathways of differentation. On the one hand they may differentiate into macrophages ("distant from tubules") or, alternatively, into epitheloid cells ("adjacent to tubules"). The latter, through cell fusion, develop into multinucleated giant cells of the Langhans' type. The cytoplasmic components of the epitheloid cells and the multinucleated giant cells should be interpreted as an activation of cellular biosynthesis. Its products, upon being secreted at the immunodefective basement membrane, will obviously serve immune defense mechanisms.

An electron microscopic study of central nervous system sarcoidosis

Although the fine structure of extraneural sarcoidosis is well documented, ultrastructural study of central nervous system (CNS) sarcoidosis has been limited. Electron microscopic (EM) examination of 3 biopsy cases of CNS sarcoid revealed a mixed cellular population of lymphocytes, epitheloid cells, and multinucleated giant cells. The epitheloid and multinucleated giant cells shared common ultrastructural features of nuclei and cytoplasm. In addition, they displayed similar specializations of the cell surface, including subplasmalemmal linear densities (SLD) and villous projections. These findings recapitulate those described in extraneural sarcoidosis and other granulomatous disorders. This supports the contention that the macrophages or epitheloid cells present in CNS lesions are derived from the same mononuclear phagocytic system as their systemic counterparts.

Giant cell stromal reaction in squamous cell carcinomata. Electronmicroscopic and ultrahistochemical observations on the genesis and functional activity of multinucleated giant cells in bleomycin-induced tumor regression

Ten cases of oral squamous cell carcinoma, treated by bleomycin, were studied by electron microscopy with particular regard to the stromal reaction. The genesis and phagocytic function of multinucleated giant cells of foreign body type were observed. These cells phagocytize devitalized, keratinized tumor cells in particular. Their genesis from monocytic macrophages and endocytosis of large keratinized tumor cells are described in detail. Both phenomena are connected and the mode of formation of the cells results in functional specialization. The initial stages of intracellular digestion do not seem to take place within membrane limited vacuoles but in specialized cytoplasmatic areas which are formed around the ingested material. These contain high concentrations of hydrolases, sealed off from the rest of the cell by a clear zone of organell-free cytoplasm. This unique form of phagocytosis and digestion ("gigantophagocytosis*) is only possible in these highly specialized giant cells and explains their biological significance. It is likely that secondary lysosomes are formed in subsequent stages of digestion. The difference between our results and the experimental observations of other authors are discussed.