IMMUNE-REACTION INDUCED BY X-RAYS AND PIONS AND ITS STIMULATION BY SCHIZOPHYLLAN (SPG)

Female C57BL/6 mice aged 6-8 weeks with transplanted Lewis lung cancer cells were used to investigate the anti-tumour effects and immune rea ctions in tumour tissue induced by X-ray and pion irradiation and thei r modification by schizophyllan (SPG). The effect of SPG on the rate o f lung metastasis and the survival time of the mice was also studied u sing the same tumour system. These studies showed that in this tumour system the 'practical' relative biological effectiveness (RBE) of pion s was 1.33 in the dose ranges used (3 Gy x 4 = P3; 6 Gy x 4 = P6). SPG increased the suppression of tumour growth associated with moderate d oses of radiation: X-rays (4 Gy x 4 = X4) or P3. SPG also decreased th e number of lung metastases and prolonged the life span of the mice, t hese effects being independent of radiation. The addition of SPG to ra diation increased both the macrophage infiltration and T-lymphocyte in filtration in the local tumour and the lung nodules. There did not app ear to be any major differential effect of SPG on the pion-treated mic e compared with those treated with X-rays.