The immunological response of Wistar rats to the intracranially implanted C-6 glioma cell line

The immune response of Wistar rats to the intracranial inoculum of 1 X 10(5) C-6 glioma cells was evaluated. The growth of these cells disrupted the blood-brain barrier by day 9. The rats with the implanted tumor cells died between three to four weeks following injection. No significant cell-mediated cytotoxicity against 51Cr labelled C-6 cells was seen in the short term (4 hours) cytotoxicity assay with spleen cells obtained from glioma-bearing rats at any stage of tumor growth. In the long term (18 hours) cytotoxicity assay, significant activity was detected using whole, adherent and nonadherent spleen cells from glioma-bearing rats at every assessment point during the growth of the tumor, but this cytotoxicity was also seen in normal rat splenocytes. The lack of cell mediated cytotoxicity above normal values was not due to a generalized immunosuppression since splenocytes from glioma bearers were found to have responses to Con A comparable to normal controls. However, normal or glioma-bearer splenocytes showed augmented cytotoxicity in the presence of serum obtained from rats bearing a glioma tumor starting by day 13 of tumor growth and rising in cytotoxic activity until death. This activity was not seen with normal serum. The glioma-bearer serum, though not cytotoxic to the C-6 cells alone, became cytotoxic with the addition of rabbit complement. These data indicate that the growth of intracranially implanted glioma cells in rats elicits primarily a humoral cytotoxic immunity without a significant cell-mediated immunity. This humoral immunity develops after the breakdown of the blood-brain barrier.