Xanthogranulomatous cholecystis. Cell composition and a possible pathogenetic role of cell-mediated immunity

Thirty-three cases of xanthogranulomatous cholecystitis (XGC) exhibiting the typical morphologic features were studied by light and electron microscopy and immunohistochemical techniques. Incidence of XGC was 4.2% of the surgically resected gallbladder diseases. Histologically, the granulomatous lesion of XGC principally consisted of accumulations of foam cells and lymphocytes. Variable numbers of multinucleated giant cells, granulocytes and fibroblastic cells were also noted. With respect to the origin of foam cells, it was considered that the vast majority of foam cells were derived from monocytes/macrophages because they were invariably positive for KP1, HAM56, CD11b and CD68. Interspersed among macrophage foam cells, many T lymphocytes were identified. The subtyping of T cells indicated a heterogenous population composed of both CD4+ and CD8+ lymphocytes typically in a ratio of 1:2. Macrophages and T lymphocytes demonstrated a marked expression of HLA-DR antigen. Electron microscopic and immunohistochemical double-staining observation demonstrated intimate apposition of T lymphocytes to macrophages or macrophage foam cells. The results indicate that XGC is a granulomatous disorder characterized by accumulations of macrophage foam cells and T cells. Delayed type hypersensitivity reaction of cell-mediated immunity may be implicated in the pathogenesis of XGC.