Immunohistochemical demonstration of immunoglobulins and albumin in human brain tumors.

Routinely processed biopsy material, including 56 gliomas of varying malignancy, 10 meningiomas, 10 brain metastases and 12 brain abscesses, was examined for the presence and distribution of IgG, IgA, IgM, IgD and albumin using the unlabeled antibody peroxidase-antiperoxidase technique. In all specimens the deposition of stained immunoglobulins (Ig) was strictly associated with that of albumin even on cell surfaces. Thus there was no evidence for specific membrane binding or cytotoxicity. The interstitial proteins demonstrated are most likely derived from the plasma by blood-brain barrier breakdown which occurs in nearly all tumors and abscesses. Obvious intracellular staining for Ig and albumin was seen in glioma cells and astrocytes only. This is suggested to be due to active protein uptake as a specific feature of astrocyte differentiation which decreases with malignancy and is lost in glioblastomas. Evidence for local Ig production was found in 8 out of 10 metastases with striking IgG- and IgA-positive plasma cells within lymphocytic infiltrations and in one meningioma showing conspicuous plasma cells components. No glioma contained Ig-bearing plasma cells, though round cell infiltrations were present in 64% of the unselected cases. The significance of these findings regarding the immunological situation in brain tumors is briefly discussed.