Effects of ionizing radiation and cyclophosphamide on hematopoietic and immune functions in mice

Objective: To compare the injury and recovery effects of ionizing radiation and chemotherapy on hematopoietic and immunologic functions in mice and provide the experimental evidence for clinical treatment of acute radiation syndrome (ARS). Methods: Mice were divided into radiation groups exposed to 2, 4, 6 and 8 Gy of ⁶⁰Co γ-rays and chemotherapy groups administered with cyclophosphamide (CTX) at dosages of 100, 150, 200 and 250 mg/kg. Blood routine examination was performed in all groups. According to the pilot result of blood routine examination, 2 Gy group and 200 mg/kg group were selected to analyze the immunocytes subsets (T cells, B cells, NK cells and Tregs). Results: In each group, the number of white blood cells (WBC) in peripheral blood decreased and dropped to a minimum level at 4 d. The chemotherapy and 2 Gy group quickly rebounded to restore at 10-12 d, but 4 Gy group recovered more slowly. There was no significantly different between 2 Gy group with 200 mg/kg chemotherapy group and there was significantly different between other doses of radiation groups with chemotherapy groups (t = 2.531, 2.343, 2.074, P < 0.05). The numbers of CD8+ T cells were decreased significantly in irradiated group than chemotherapy group(F = 5.026, P < 0.05). The number of regulator T cells (Tregs) were higher obviously increased in irradiated group, and decreased in chemotherapy group, the difference was statistically significant (F = 4.848, P < 0.05). But the number of CD4+ T cells, B cells and NK cells were no significant differences between radiation group and chemotherapy group. Conclusions: The recovery of immunocytes in ionizing radiation group was slower than that in chemotherapy group. Chemotherapy had less effect of immune suppression and damage compared with ionizing radiation. Delay of immunologic reconstitution is the main cause of ARS death to get effective therapy result, the application of hematopoietic stimulating factor may be necessary. (authors)