Macrophage subpopulations in the thymic hyperplasia of patients with myasthenia gravis.

Abstract

Macrophages were studied in sections of the thymus from patients with Myasthenia Gravis, using a panel of monoclonal antibodies against the monocyte/macrophage lineage. In normal areas, CD14 and CD35 were preferentially expressed in the medulla while RM3/1 and 25F9 markers stained essentially cortical macrophages. CD11c-labelled cells were densely located throughout the thymus. The antibody 27E10 recognized clusters of cells located around or in the perivascular areas, that could be migrating monocytes. In the germinal centers, cells were stained with CD14, CD35, CD11c and 25F9 but not with RM3/1 and 27E10 markers. The numbers of CD14- and CD35-positive cells were significantly increased in Myasthenia Gravis thymic hyperplasia compared to control thymus (p < 0.025 and p < 0.01, respectively). This increase was clearly due to the higher number of positive cells in the germinal centers and in the areas surrounding the lymphoid follicles. The potential role of these cells in accessory cell function and antigen presentation could be relevant in terms of intrathymic sensitization and autoantibody production that have been demonstrated in thymic hyperplasia from Myasthenia Gravis patients.