Immunohistochemical characterization of epithelioid cells

: Focally aggregated epithelioid cells and granulomatous epithelioid cell reactions of different genesis were investigated immunohistochemically by means of PAP method according to Sternberger. We studied the presence of histiocytic markers lysozyme and alpha 1-antichymotrypsin, the content of albumin and of immunoglobulins and the question of immunophagocytosis and the presence of fibronectin. Various forms of activation of epithelioid cells as well as histiocytes and Langhans giant cells were found thereby. In the former, a phagocytosis could never be demonstrated, whereas this was true in histiocytes and giant cells. Fibronectin was not found in epithelioid cells. The findings suggest that epithelioid cells are a specific form of reaction of histiocytic elements. Thus they are a special reaction of MPS in a multiple causal genesis and a morphogenesis according to its own characteristics within a hypersensitivity reaction of a delayed type. Epithelioid cells modulate the immune response and in this way the tissue reaction.