Epithelioid cell

[1][2][3] Structurally, epithelioid cells (when examined by light microscopy after stained with hematoxylin and eosin), are elongated, with finely granular, pale eosinophilic (pink) cytoplasm, and central, ovoid nuclei (oval or elongate), which are less dense than that of a lymphocyte.

When examined by transmission electron microscopy in epithelioid cells in the field of Golgi lamellar complex are taped not only zonated, but also sleek vesicles with dense center, and also great many (more than 100) large granulas with diameters up to 340 nm and with finegranular matrix more light than in macrophage granulas, sometimes with perigranular halo.

It is exhibited that the dense webs of intermediate filaments, bound with cores, mitochondrions and other organelles, are supervised everywhere in cytoplasm of epithelioid cells.

Granuloma formation is associated with pathogens that have learned to evade the host immune system by various means like resisting phagocytosis and killing within the macrophages.

Granuloma formation is also the feature of many more contemporary conditions, like fungal infections, sarcoidosis and Crohn's disease.

In experiments on rabbits, Alexandre Yersin (1888) and Amédée Borrel (1893) showed that epithelioid cells are formed from blood mononuclear leukocytes.

[12] Later in a study of a similar plan, Jerry S. and Weiss L. (1966), when using cultures of mixed blood leukocytes of chicken (separated from cardiac blood of Rhode Island Red) and electron microscopy, showed that the transformation of monocytes of chicken in epithelioid cells begins in culture on 3–4 days and ends on 5–6 days.

[6] Since all previous researchers have indicated that epithelioid cells are formed from monocytes, and monocytes and macrophages were combined into a single mononuclear phagocyte system, Van Furth et al. (1972), referring to the work of Sutton J. and Weiss L. (1966),[6] formally attributed epithelioid cells to the mononuclear phagocyte system.

At the same time, they came to the very cautious conclusion that "the epithelioid cells occurring in these lesions also arise from monocytes or macrophages.

The present ultrastructural and immunoelectron microscopic study of epithelioid cell granulomas provides further arguments in favor of this hypothesis.

Using mouse inbred lines, as opposed to susceptibility to Mycobacterium tuberculosis, it was shown that the numbers of pre-epithelioid monocytic cells, formed in chronic inflammation, are genetically determined.

Epithelioid cells formed in culture of mouse peritoneal cells, stimulated by inactivated Mycobacterium tuberculosis , in a micro-chamber for lifetime observation; 14 days of cultivating. Numerous secretory granules are visible in the cytoplasm of cells. In the culture medium epithelioid cell granules and apoptotic bodies from macrophage are visible. Dystrophic altered macrophages are colored red. A method of interferential contrast in polarized light.
Epithelioid cells gather around the focus of necrosis, in direct contact with the necrotic masses, forming a kind of boundary zone.
Epithelioid cells (polarized form, nucleus color - green) and macrophages (nucleus color – red) in peritoneal cell culture of mice, stimulated by inactivated Mycobacterium tuberculosis , on the 10th day of cultivation. The pseudo color image was obtained by color coding of different optical densities in a photo of cells, stained by Azure-Eosine. The shape of cells is determined by their cytoskeleton, and the color characterizes their different cytomorphology.
Fragment of the outer edge zone of tuberculosis epithelioid cell granuloma. In the lower part – a layer of epithelioid cells, in which Langhans giant cell begins to form, as a result of the fusion of epithelioid cells. In it, we can notice the division of the cell nucleus of epithelioid cells, from which smaller nucleus are formed. Single pycnotic and apoptotically altered macrophages are found among epithelioid cells. Above the zone of epithelioid cells is a layer of fibroblasts that form a kind of “capsule”. In the upper part – a layer of cells consisting of lymphocytes. The video shows the result of optical scanning (when using Phase-contrast microscopy ) when changing the depth of field .