Immunocytochemical demonstration of IgG in human brain tumors (author's transl)

Abstract

In the past several years a number of immunological studies of human brain tumors suggesting evidence of the existence of certain brain tumor-specific antigens have been extensively performed. However, there is other evidence that suppressive factors not only exist in the sera of patients with malignant brain tumors but also bind to lymphoid cells and that they can specifically modify the cell-mediated immune mechanisms to the tumors of the central nervous system. Therefore, humoral immunity seems to be playing an important role in the cell-mediated immune responses against brain tumors especially in relation to both antibody dependent cell-mediated cytotoxicity (ADCC) and blocking factor(s). In the present study, 23 human brain tumors (9 glioblastomas, 5 astrocytomas, 1 ependymoma, 1 medulloblastoma, 5 ineningiomas and 2 metastatic cancers) obtained at craniotomy have been examined to determine the presence or absence of immunoglobulin G (IgG) and immunoglobulin M (IgM) in the tumor tissue by the direct immunoperoxidase method using enzyme-labeled antigen binding Fab' fragments. Of 23 human brain tumors examined, 3 glioblastomas, I ependymoma, 1 medulloblastoma, 5 meningiomas and 1 metastatic cancer displayed unequivocally positive immunocytochemical reaction for IgG in the tumor tissue. The intensity of staining differed among the tumor cells and IgG was mainly localized on the surface of the tumor cells by immunoelectron microscopy. On the other hand, IgM was not observed in any tumor tissues except for the positive staining limited within the capillary lumen of the tumors. In the meningiomas, the positive staining for IgG was more prominent around the capillaries, psammoma bodies and in the whorl formation, suggesting possible contribution of humoral immune reaction in the mechanisms of whorl or psammoma body formation. Although it is not clear as to whether or not IgG distributed on the surface of tumor cells acts to suppress or accelerate cellular immunity and complement-dependent cytolysis of tumor cells in vivo, our present immunocytochemical findings suggest tumor-specific antibodies among IgG “coating” on the cells of certain human brain tumors.