The Structural Organization of Thymus and Cellular Composition of Blood under Experimental Exposure to Cold

The immune system is a unique defence mechanism.Due to the well-coordinated work of the entire functional immune system, the body can resist numerous amounts of negative factors.Cold exposure is one of the factors that negatively impact the body.The effect of experimental cold stress on the morphofunctional state of the thymus and the cellular composition of the blood of rats, depending on the time of their exposure, was studied.The effect of cold exposure was studied by placing animals in individual cages in the "Vestfrost" refrigerator (Denmark) at a temperature of 10±2 °С for 1 hour at the same time of the day for 7, 14, 21, and 30 days.Analysis of the research results showed that on the first and late days of the experiment, there is a redistribution of the volume and cellular composition of various structural and functional zones, indicating a decrease in the functional activity of the thymus, an increase in the death of lymphocytes in the process similar to apoptosis, a decrease in mitotic activity and the accumulation of macrophages.At the same time, on the 14th day of the experiment, the development of compensatory-adaptive changes in the thymus in response to cold exposure, manifested in the form of activation of cell division in the cortex and the cortical-medullary zone, is noted.The results of a study of the cellular composition of blood showed that as a result of exposure to cold, a specific immune response is stimulated, as indicated by an increase in the number of lymphocytes in the blood.A decrease in the number of leukocytes indicates suppression of nonspecific cellular immunity in experimental animals.