Cellular immunity in rats with primary brain tumors: inhibition of macrophage migration by soluble extracts of avian sarcoma virus-induced tumors.

Rats bearing primary tumors of the brain induced by avian sarcoma virus (ASV) were studied with the migration-inhibition factor (MIF) assay for the presence of cell-mediated immunity to tumor-associated antigens. Astrocytomas and sarcomas of the brain were induced in 34 neonatal F344 rats by the intracerebral inoculation of Bratislava-77 ASV. At weekly intervals from 4 to 9 weeks after the inoculation with virus, peritoneal exudate cells (PEC) from rats bearing brain tumors were tested an an MIF assay against soluble and KCl-treated extracts of a syngeneic, ASV-induced sarcoma. Incubation of the PEC with a soluble extract of syngeneic liver or with a KCl extract of a syngeneic, chemically induced tumor served as controls. Of 14 rats tested against the soluble tumor extract, 6 (43%) had statistically significant inhibition of migration (P less than or equal to 0.05). Of 23 animals tested against the KCl extract, 16 (70%) had significant inhibition. Immunity to the KCl extract was significant in most rats at each period. Ten rats were tested against a KCl extract of a hamster ASV-induced tumor; 7 gad significant inhibition of migration. None of 3 tested against a soluble extract of a syngeneic, chemically induced tumor had significant inhibition. Rats bearing ASV-induced brain tumors displayed cell-mediated immunity to tumor-associated antigen or antigens of ASV-induced tumors, which could be solubilized.