Immune cells in periapical granuloma: morphological and immunohistochemical characterization.

Samples of periapical granulomas obtained from 12 patients were examined using light and electron microscopes and monoclonal antibodies. Monocytes/macrophages, lymphocytes, and plasma cells were nearly always the most abundant cell populations. Ultrastructural analysis showed close contacts between macrophages and cells of the lymphoid lineage, with the lymphoid cells frequently demonstrating blastic features. Immunohistochemical staining with the anti-interleukin 2 receptor antibody showed that the concentration of labeled cells was quite low. The vast majority were lymphocytes, though some mast cells were also labeled. Mast cells were chiefly located in perivascular areas and interleukin 2 receptor-positive mast cells were frequently associated with lymphoid cells. mast cells could be part of a negative feedback mechanism in the immune response. By releasing histamine, they would block the immune response and by absorbing interleukin 2 they would remove it as an immune system stimulant.