Immunohistochemical study of the spleen in chronic immune thrombocytopenic purpura. With special reference to hyperplastic follicles and foamy macrophages.

Abstract

To better understand immunologic and pathophysiologic changes in the spleen in chronic immune thrombocytopenic purpura. We performed immunohistochemical studies on 12 spleens of patients with immune thrombocytopenic purpura. Four spleens had prominent hyperplastic secondary follicles in the white pulp and trapping of platelet antigen (GPIIb/IIIa) in the germinal center. Four other spleens had hyperplastic follicles and foamy macrophages but no platelet antigen trapping in the germinal centers. Another four spleens had predominantly foamy macrophages but no hyperplastic follicles. Foamy macrophages were found mainly in the marginal zone; abundant platelet antigen (CD41) was present in their cytoplasm. Hyperplastic follicles in the white pulp or foamy macrophages in the marginal zone (or both) are major pathologic features in most spleens in immune thrombocytopenic purpura. The presence of platelet antigen (CD41) in the germinal centers and foamy macrophages may reflect the sites of immune reaction and platelet destruction in immune thrombocytopenic purpura.