EPITHELIOID CELL GRANULOMA

Abstract

Various studies have been carried out on factors affecting the epithelioid cell granuloma formation. From the viewpoint of histogenesis of the epithelioid cell granuloma in tuberculosis, the delayed-type hypersensitivity reaction has been found to play an important role. Recently, muramyldipeptide fraction, a minimal adjuvant-active subunit of bacterial cell walls, was found to produce the epithelioid cell granuloma.
We investigated the capacity of synthetic muramyldipeptide and its derivatives in the epithelioid granuloma formation and also in the adjuvant activities. A close correlation was pointed out between the granuloma formation and the adjuvant activities. Further, when lymphokines were injected together with muramyldipeptide, well-differentiated epithelioid granuloma developed in guinea pigs. Thus, the epithelioid granuloma formation in tuberculosis might be thought to be affected by the summation of non-specific and the specific hypersensitive responses.
In this review, we referred the regulatory mechanism of the epithelioid granuloma formation as well as the morphological and functional characteristics of the granuloma. With regard to the suppres sor cell which might play a role in regulation of the epithelioid granuloma formation, an inhibition to the granuloma formation was found by injecting a specific antigen mixed with muramyldipeptide in guinea pigs in which the specific tolerance had been induced by cyclophosphamide-sensitive suppressor cells.
Though many studies support that the epithelioid cells develop in the granuloma following differ entiation from the activated macrophages, the mechanism of the differentiation still remains enigmatic. Thus, muramyldipeptide is expected to offer the possibility of clarifying the mechanism.