Decreased phagocytic capacity of rat peritoneal macrophages following photon abdominal irradiation

Photon irradiation of the abdomen may be accompanied by complications due to a decrease in the immune defense of the recipient. Since peritoneal macrophages are an important component of the immune system, we examined the phagocytic activity and oxygen superoxide anion generation by peritoneal macrophages from rats 2 and 4 weeks after abdominal irradiation with 6 MV photons applying a single dose of 2 Gy. Two and 4 weeks after irradiation, peritoneal macrophages were harvested and their capacity to engulf latex particles and to produce oxygen superoxide anions was determined. Non-irradiated rats, treated identically otherwise, served as controls. Two weeks after irradiation the phagocytic capacity and oxygen superoxide anion generation decreased by 61 and 70%, respectively, compared with controls. This tendency persisted after 4 weeks post irradiation, the decrease in both functions being 50 and 74%, respectively. It is suggested that the altered function of peritoneal macrophages following irradiation may further compromise the immune defense in patients receiving abdominal radiotherapy.