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We studied the response of the pineal gland and organs of the immune system to melatonin treatment in Wistar rats kept under conditions of abnormal illumination regimen. The animals were kept under natural light regimen or continuous illumination for 14 days and then received daily injections of melatonin (once a day in the evening) for 7 days. Administration of melatonin to rats kept at natural light cycle was followed by a decrease in percent ratio of CD4+8+ splenocytes and CD4-8+ thymocytes. In 24-h light with the following melatonin injections were accompanied by an increase in percent rate and absolute amount of CD4+8+ cells in the spleen, and a decrease in percent rate of CD11b/c and CD4-8+ splenocytes. In the thymus amount of CD4-8+ cells increased, and absolute number of CD4+25+ cells reduced. Melatonin significantly decreased lipofuscin concentration in the pineal gland during continuous light. Direction and intensity of effects of melatonin on parameters of cell immunity and state of the pineal gland were different under normal and continuous light conditions. It should be taken into account during using of this hormone for correction of immune and endocrine impairments developing during change in light/dark rhythm.

We studied the influence of abnormal illumination regimen on cell composition of the central and peripheral organs of the immune system in ISIAH rats and control WAG rats. In ISIAH rats, 24-h illumination for 14 days led to more pronounced inhibition of cell proliferation and differentiation in the thymus and more pronounced decrease in splenocyte proliferation and T and B cell counts in the spleen in comparison with WAG rats; however, the level of antigen-presenting cells in the spleen of ISIAH increased. We concluded that ISIAH rats are more sensitive to abnormal illumination regimen than WAG rats. Twenty-four-hour illumination was associated with impairments of central differentiation of T cells and activation of systemic inflammation followed by impairment of differentiation regulation, which can aggravate metabolic dysfunctions in these animals.

The aim of this study is to investigate the influence of experimental desynchronosis on the immune system and estimate benzo[a]pyrene (BP) influence on the immune reactivity of mice under the condition of desyncronosis (DS) in comparison with intact organisms. Mice (CBA X C57BL)F1 were kept under constant light during two weeks and natural alternation of darkness and light (control group). Animals of the two groups received benzo[a]pyrene solution in olive oil. The existence of diurnal variation of cell populations of lymphoid organs and blood, humoral immune response to SRBC were revealed. Changes of diurnal dynamics of these parameters and decrease of humoral immune response to SRBC have been observed in animals kept under constant light in comparison with animals kept under standard light conditions. It is likely to indicate the development of internal DS. BP influenced the cellular composition and immune response of intact and DS animals in a different way. So, the changes of light regime lead to development of the internal DS of immune system that influenced its functional capacity and sensitivity to damaging effect of chemical ecological factor.

One of the key synchronizers of mammalian circadian rhythm is the hormone melatonin (MT) produced by the pineal gland. MT is characterized by a wide spectrum of biological activity including its immunopotentiating effect. At the same time, the results of studies dedicated to the effects and mechanisms of melatonin immunoactivity seem to be contradictory. Studies conducted by the authors of this article show that diurnal variations in MT content in blood and saliva of healthy humans demonstrate significant individual fluctuations connected with the seasonal factor. The character of MT relations with the immune system varies depending on the phase of the circadian cycle. Patients with immunopathological condition (bronchial asthma--BA) demonstrate a reduced number of correlations between MT level and immunological parameters. After treatment, the positive dynamics of immunological and clinical parameters in BA patients is associated with an increased number of correlations between the immunological status parameters and MT level in blood, which may indicate an increase in its immunoregulatory role. Administration of melatonin and amitriptyline, the inductor of its synthesis, in animals kept under continuous light helped to recover normal circadian rhythmicity in the cell content of lymphoid organs. Solving problems associated with the immunomodulating and synchronizing role of MT could give researchers an insight into the details of neuroendocrine and immune interrelations and help to develop new methods for the prevention and correction of immune status disturbances in diseases and desynchronoses (stresses, jet lags, shift and night work, etc.).

Levels of the major regulatory subpopulations of lymphocytes in the thymus and spleen and blood lymphocyte dehydrogenase levels were measured in male mice with aggressive and submissive patterns of behavior formed over 10 or 20 aggressive confrontations leading to repeated experience of victory or defeat. The results showed that repeated experience of social confrontation non-specifically increased the proportion of segmented neutrophils and lactate dehydrogenase activity in both participants in aggressive encounters, and decreased the numbers of CD4+ and CD8+ T-lymphocytes in the spleen. Succinate dehydrogenase specifically decreased in the lymphocytes of aggressive mice and increased in the lymphocytes of submissive mice. The proportion of CD4+ T-lymphocytes in victims' thymuses also decreased. Changes in metabolic measures and percentage ratios of lymphocyte contents were dynamic and depended on the duration of confrontational interactions.

The biological rhythmological programme of the immune system is a constituent of the body's common biological rhythmological programme. Its pattern seems to be genetically determined and reflects the functional status of the system. The chronobiological mechanisms responsible for the regulation of immune functions lie in the presence of certain phasic interrelations between the biological rhythms of the synthesis and production of regulatory agents on the one hand, and those of the receptor system and metabolic potential of immunocompetent cells on the other. The facts given in the paper may be a basis for a chronobiological approach to better understanding the mechanisms of the physiology and pathology of the immune system. The medical significance of study of the structural and temporal pattern of the immune system consists in the development of new techniques for diagnosis, prognosis, therapy, and assessment of risk factors in immunopathological conditions.

The effects of LPS from E. coli on DNA-binding activities of PPARα and PPARγ in the liver and immune system parameters of were studied in hypertensive ISIAH rats and normotensive WAG rats. In ISIAH rats characterized by low basal level of PPARα, PPARγ, and HDL, the response of the peripheral immune system compartment to LPS was more pronounced and was not associated with decrease in DNA-binding activities of PPARα observed in WAG. Proinfl ammatory stimulus did not induce proliferative changes in the thymus of ISIAH rats, which can refl ect impaired relationships between the central and peripheral organs of the immune system. The character of regulatory interactions between PPARα and immune cells can differ in various rat strains and depend on initial PPARα activity, HDL level, specifi c features of immune status, resistance to stress, and hormonal and metabolic background. [ABSTRACT FROM AUTHOR]