Comprehensive study of hematopoietic changes in non-irradiated mice kept in contact with irradiated animals

Over the past decades, numerous studies have investigated the quantitative and qualitative patterns of radiobiological effects. The radiation-induced “bystander effect” at the inter-organismal level was represented by experiments obtained on hematopoietic organs and peripheral blood populations of irradiated and non-irradiated mice. It was shown that in non-irradiated mice in contact with irradiated animals (cages with a septum), on the 3-rd day after the beginning of the experiment, a significant decrease in the relative number of lymphocytes (p=0.047) was observed, accompanied by an in-crease in the percentage of eosinophils (p=0.05). The eosinophil index was also significantly in-creased in the “bystander” animals kept in cages without a septum (p=5E-5). On the 14-th day, both versions of the experiment also demonstrated a highly significant increase in the relative number of eosinophils compared to the control (p=4E-3 and p=8E-4 for the cage without septum and with the septum, respectively). At the same time, there was a tendency to an increase in the number of normo-chromatophilic erythrocytes with micronuclei (cages with a septum, p=0.09). In unexposed “by-stander” animals in the remote period (30-th day) from the beginning of the experiment, the eosinophil content continues to increase compared to the unexposed control (cages without septum, p=2E-5). On 60-th day, this group of non-irradiated mice showed a decrease in the absolute number of leuko-cytes, the percentage of lymphocytes, and an increase in the proportion of neutrophils compared to the control group (p=0,06, p=0,038, p=0,02, respectively), and on 90-th day, there was a tendency to an increase in the frequency of monocytes (p=0.05) and a significant decrease in nucleated bone marrow cells (p=0.02). On the 30-th day, the “bystanders” kept with the irradiated mice in septal cages showed a decrease in the percentage of lymphocytes (p=0.01), accompanied by an increase in the number of neutrophils (p=0,04), monocytes (p=0,04) and eosinophils (p=0.08). On 90-th day, a sig-nificant decrease in the proportion of lymphocytes (p=0,01) was revealed in these animals along with an increase in the relative number of eosinophils (p=0.02) and monocytes (p=0.05), as well as a tendency to an increase in the level of normochromatophilic erythrocytes with micronuclei compared to the control group (p=0.06). Thus, the experiment showed systemic disorders of hematopoiesis in non-irradiated mice in contact with irradiated animals, with the prevalence of long-term effects accompanied by a significant change in the percentage of leukocytes of different subpopulations.