Effect of Ionizing Radiation on the Host Resistance Against Listeria Monocytogenes Infection and the Cytokine Production in Mice

Oh, Yoon Kyeong; Chang, Mee Young; Kang, In Chol; Oh, Jong Suk; Lee, Hyun Chul

Abstract

PURPOSE
To evaluate the qualitative immunologic changes by ionizing radiation, we studied the altered capacities of the macrophages and lymphocytes to produce cytokines in conjunction with resistance to Listeria monocytogenes (LM) infection in mice.
MATERIALS AND METHODS
BALB/c mice and Listeria monocytogenes were used. The mice were infected intraperitoneally with 105LM at 1 day after irradiation (300cGy) and sacrificed at 1, 3, 5 days after infection, and then the numbers of viable LM per spleen in the irradiated and control group were counted. Tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-2 (IL-2), and nitric oxide (NO) were assessed after irradiation.
RESULTS
Under gamma-ray irradiation with a dose range of 100-850cGy, the number of total splenocytes decreased markedly in a dose-dependent manner, while peritoneal macrophages did so slightly. Cultured peritoneal macrophages produced more TNF-alpha in the presence of lipopolysaccharide (LPS) during the 24 hours after in vitro irradiation, but their capacity of TNF-alpha production showed a decreased tendency at 5 days after in vivo total body irradiation. With 100cGy and 300cGy irradiation, cultured peritoneal macrophages produced more NO in the presence of LPS during the 24 hours after in vitro irradiation than without irradiation. Activated splenocytes from irradiated mice (300cGy) exhibited a decreased capacity to produce IL-2 and IFN-gamma with Concavalin-A stimulation at 3 days after irradiation. When BALB/c mice were irradiated to the total body with a dose of 300cGy, they showed enhanced resistance during early innate phase, but a significant inhibition of resistance to LM was found in the late innate and acquired T-cell dependent phases.
CONCLUSION
These results suggest that increased early innate and decreased late innate and acquired immunity to LM infection by ionizing radiation (300cGy) may be related to the biphasic altered capacity of the macrophages to produce TNF-alpha and the decreased capacities of the lymphocytes to produce IL-2 and IFN-gamma in addition to a marked decrease in the total number of cells.