QUINOLINATE IMMUNOREACTIVITY IN EXPERIMENTAL RAT-BRAIN TUMORS IS PRESENT IN MACROPHAGES BUT NOT IN ASTROCYTES

Experimental tumors of the central nervous system were investigated wi th antibodies to quinolinate to assess the cellular distribution of th is endogenous neurotoxin. In advanced F98 and RG-2 glioblastomas and E 367 neuroblastomas in the striatum of rats, variable numbers of quinol inate immunoreactive cells were observed in and around the tumors, wit h the majority being present within tumors, rather than brain parenchy ma. The stained cells were morphologically variable, including round, complex, rod-shaped, and sparsely dendritic cells. Neuroblastoma and g lioma cells were unstained, as were neurons, astrocytes, oligodendrocy tes, ependymal cells, endothelial cells, and cells of the choroid plex us and leptomeninges. Glial fibrillary acidic protein immunoreactivity was strongly elevated in astrocytes surrounding the tumors, Dual labe ling immunohistochemistry with antibodies to quinolinate and glial fib rillary acidic protein demonstrated that astrocytes and the cells cont aining quinolinate immunoreactivity were morphologically disparate and preferentially distributed external and internal to the tumors, respe ctively, and no dual labeled cells were observed. Lectin histochemistr y with Griffonia simplicifolia B-4 isolectin and Lycopersicon esculent um lectin demonstrated numerous phagocytic macrophages and reactive mi croglia in and around the tumors whose distribution was similar to tha t of quinolinate immunoreactive cells, albeit much more numerous. Dual labeling studies with antibodies to quinolinate and the lectins demon strated partial codistribution of these markers, with most double-labe led cells having the morphology of phagocytes. The present findings su ggest the possibility that quinolinate may serve a functional role in a select population of inflammatory cell infiltrates during the immune response to brain neoplasms. (C) 1997 Academic Press.