Abstract
The effects of irradiation on major histocompatibility complex (MHC) expression and lymphocytic infiltration in the normal rat brain and the 9L gliosarcoma brain tumor model were examined. Doses of irradiation administered were biologically equivalent to that used in the treatment of patients with malignant gliomas. No significant change in immune parameters was observed following irradiation in the normal rat brain. In the 9L gliosarcoma model irradiation did not suppress MHC expression or lymphocytic infiltration. These findings suggest that prior exposure to therapeutic irradiation need not adversely affect subsequent immunotherapies, and provide a foundation for future studies of immunomodulation in the irradiated brain.