Evaluation of the level of gamma radiation dose on some immune system parameters against cancer

Abstract

The positive impact of exposure to low-dose gamma irradiation (LDR) on tumor regression and immune response has recently been emphasized. The present study aimed to investigate the T-helper 1 / T-helper 2 (Th1/ Th2) cytokine balance, serum protein changes in male BALB/c Ehrlich Ascites Carcinoma (EAC) bearing mice exposed to two low doses(0.4Gy or 0.8Gy) of gamma irradiation. Seventy two male BALB/C mice were divided into six groups. Group1: normal control; Group2&3:mice were exposed to γ-irradiation at 0.4 and 0.8 Gray, respectively two times weekly for 3 weeks; Group4 (malignant control):mice were injected subcutaneously with 2×10⁶ Ehrlich Ascites Carcinoma (EAC) cells/mouse; Group5&6: mice were injected by EAC cells and exposed to γ-irradiation at 0.4 and 0.8 Gray, respectively two times weekly for 3 weeks, eight days after tumor transplantation. Data from the present study reported that two low-doses of γ- irradiation significantly increase the levels of serum IL2, IL6 and TNFα and a decrease the serum IL10 level in comparison to malignant control mice. The IL2 /IL-10,IL-6/IL-10 and TNFα/IL-10 (Th1/Th2 balance), were significantly increased in all tested groups when compared with control (P<0.05). Exposure to 0.8 Gy dose, however, induced significant elevation in all ratios in comparison to exposure to 0.4 Gy dose. This was associated with significant reduced tumor growth in mice implanted with Ehrlich Ascites Carcinoma, which was more pronounced in mice exposed to 0.8 Gy than mice exposed to 0.4 Gy dose. In conclusion, the present study suggests a possible immunomodulatory role of LDR as it was associated with Th1 cytokine polarization response, and 0.8 Gy have more positive effect than 0.4 Gy. It also reinforces the beneficial effect of accumulated dose of total body irradiation (0.4Gy or 0.8Gy) in the regression of implanted Ehrlich Ascites Carcinomain BALB/c mice.