Macrophages in periapical lesions

Macrophages are major constituents of periapical granulomas. They have a ce ntral protective role in both innate immunity and adoptive, antigen-specifi c immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen-activated T-lymphocytes; by bacterial end otoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develo p independently of T-lymphocytes. This observation reveals the major role t hat the activated macrophage may have in the formation of periapical lesion s. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone-resorbing cytokines in the periapical granuloma. Understanding the cen tral role of the activated macrophage in the formation as well as the perpe tuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.