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Interstrain differences in behavior and parameters of the immune system of CBA and C57BL/6 mice with round the clock coverage (KO) were investigated. Open field, light/dark, acoustic startle response, forced swimming, elevated plus-maze, passive avoidance were used for measuring emotional behavior and memory. The number of lymphocyte subpopulations CD3+, CD4+8-, CD4-8+, CD4+8+, CD19+, CD3+hi spleen and thymus, the ratio of cells in different phases of the cell cycle was determined by flow cytometry. C57BL/6J mice strictly increased anxiety in response to the KO compared to CBA mice. Moreover, KO-treated C57BL/6J mice impaired the passive avoidance learning. We found that KO evoked significant changes in the cellular composition of the thymus and decrease of thymocytes proliferation in C57BL/6J mice. In opposite KO-treated CBA mice showed change of splenic cellular structure with increased % CD19+ cells and the proliferation of splenocytes. Our study demonstrated genotype-dependent reactions of the nervous and immune systems in response chronic constant light.

In this work the correlation analysis was applied to detect the integrated response of the pineal gland (PG) and immunocompetent organs of male Wistar rats in response to administration of melatonin (MT) in light regime disturbances. Animals were kept for 14 days under natural or continuous light (CL). Then for 7 days they received the injections of either 0.9% solution of sodium chloride or MT, after which the rats were decapitated and the mass of their body, PG, thymus and spleen was determined. The lymphocyte subpopulations of the thymus and spleen were studied by flow cytometry. The amount of lipofuscin in PG was assessed by the intensity of autofluorescence in organ frozen sections in 560-600 nm wavelength range. It was found that under the influence of MT, the number of intraorgan correlations in the immune system increased, regardless of the light regime. In animals on CL treated with MT, the number of interorgan connections was reduced, while negative correlations appeared between PG lipofuscin content and cellular composition of the spleen. The synchronizing and adaptogenic effects of MT were most pronounced under conditions of CL.

The study of the immune system of mice of CBA (n=7) and C57BL/6 (n=7) strains was performed during a 12-hour photoperiod (12:12) and round-the-clock illumination (RI) in December and March. The numbers of CD3+, CD4+8-, CD4-8-, CD4+8+, CD19+, CD3+hi lymphocyte subpopulations in the thymus and spleen, as well as the proliferative activity of thymocytes and splenocytes were measured by flow cytometry. It was found that the most pronounced. interstrain differences in the cellular composition of the thymus were observed in March, while those in the cellular composition of the spleen were detected in December. Overall, in C57BL/6 mice as compared with CBA mice, the number and proliferative activity of the cells of lymphoid organs was increased. In December, the influence of RI on the cellular composition of the thymus was more pronounced in C57BL/6 mice, while the effect on cellular composition of the spleen was greater in CBA nice. In March, after exposure to RI, a number of CD3+, CD19+ and CD4+8-splenocytes was increased in CBA mice, while it was decreased in C57BL/6 mice. In C57BL/6 mice, after exposure to RI, the proliferative activity of thymocytes decreased in winter and increased in spring . Interstrain and seasonal differences in the cellular composition of lymphoid organs in CBA and C57BL/6 mice, with a photoperiod of 12:12 and RI should be taken into account in experimental work with aninials of different genotypes in different seasons of the year.