title: Enhanced lymphocyte-mediated killing of tumour cells after tumour irradiation in vivo.
abstract: The effect of local X-irradiation of a syngeneic carcinoma of fibrosarcoma growing in the leg of W/Fu rats on the ability of host spleen lymphocytes to kill syngeneic and allogeneic tumour cells in vitro was examined. Lymphocytotoxicity was found to be enhanced one day after local X-irradiation (4000 R) when compared with unirradiated tumour-bearing rats (p = 0.05 to 0.01). This enhancing effect of local irradiation was not observed when the lymphocytes were tested 1 week or later after X-irradiation, nor when normal legs of non-tumour bearing rats were irradiated. Mechanisms which might possibly explain these results are a reduction in release of tumour-specific antigen which can act as an inhibitor of cell-mediated cytotoxicity, or depletion of suppressor cells in the lymphocyte population. These findings may be relavant to clinical studies of cellular immunity in patients undergoing radiotherapy of malignant tumours.
mesh_terms: D000818:Animals; D003602:Cytotoxicity, Immunologic / Q000528:radiation effects*; D005354:Fibrosarcoma / Q000276:immunology / Q000532:radiotherapy; D005796:Genes; D008214:Lymphocytes / Q000276:immunology*; D008325:Mammary Neoplasms, Experimental / Q000276:immunology / Q000532:radiotherapy; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000276:immunology / Q000532:radiotherapy*; D051381:Rats; D014965:X-Rays