Endothelial dysfunction markers and immune response indices in cosmonauts' blood after long-duration space flights.

Space flight factors are known to cause a malfunction in the human immune system and lead to damage to blood vessels. The hemostatic function of endothelium during space missions and its interaction with human immunity has not been determined so far. In this work, we investigated the markers of endothelial activation and damage (plasma concentrations of soluble thrombomodulin fraction (sTM), von Willebrand factor (vWF), highly sensitive C-reactive protein (hs-CRP)), as well as the level of D-dimer and compared them to the immunological parameters characterizing the state of human humoral and cellular immunity. The immune status of long-duration ISS crewmembers was assessed by whole-blood testing, and comprehensive postflight immune assessment included the analysis of leukocyte distribution. Flow cytometry was applied to determine the absolute counts and the percentage of lymphocyte subsets: B cells (CD19+), T cells (CD3+, CD3+CD4+, CD3+CD8+), NK cells (CD3-CD16+CD56+, CD11b+CD56+), and activated subsets (CD3+CD25+ and CD3+HLA-DR+). The in vitro basal cytokine production was investigated in whole blood cell culture. The cytokines IFN-gamma, IL-1-beta, IL-4, IL-6, IL-10, IL-18, and TNF-alpha were measured in plasma and the 24-h supernatants by a sensitive enzyme-linked immunosorbent assay. A significant increase in the plasma levels of vWF and hs-CRP and a decrease in the concentration of sTM after spaceflights were detected. Divergent changes in the parameters characterizing the state of the immune system were observed. We propose that the changes revealed may lead to an increase in the procoagulant activity of blood plasma, suppression of protein C activation and thrombin inhibition, as well as to an increase in the adhesive-aggregate potential of platelets, especially in case of changes in the rheological characteristics of blood flow during re-adaptation to ground conditions. We also speculate that the immune system might play an important role in vessel damage during long-duration missions.

The impact of short-term confinement on human innate immunity.

During space missions cosmonauts are exposed to a myriad of distinct stressors such as radiation, overloads, weightlessness, radiation, isolation in artificial environmental conditions, which causes changes in immune system. During space flights it is very difficult to determine the particular factor associated with the observed immunological responses. This makes ground-based experiments examining the effect of each space flight associated factor along of particular value. Determining mechanisms causing alterations in cosmonauts' immunity can lead to potential targets for different countermeasures. In the current article we present the study of the early period of adaptation of human innate immunity of 6 healthy test-subjects, 4 males and 2 females aged 25 through 40, to isolation factors (hypodynamia, psychological stress, artificial environment). We measured multiple parameters characterizing innate immunity status in blood samples at chosen time points before, during and after the mission. In the experiment, highly enhanced cytokine responses were observed upon ex vivo antigen stimulations in comparison to baseline values. For cellular parameters we found multidirectional dynamics with a persistent prevalence of increasing TLRs+ monocytes as well as TLRs expression. Our study provides evidence that even a short-term confinement leads to immune changes in healthy humans that may trigger aberrant immune response.

[TOLL-LIKE RECEPTORS IN COSMONAUT'S PERIPHERAL BLOOD CELLS AFTER LONG-DURATION MISSIONS TO THE INTERNATIONAL SPACE STATION].

Studies of Toll-like receptors (TLR) in 20 cosmonauts-members of long-duration (124-199-day) missions to the International space station evidenced changes in relative and absolute counts of peripheral blood monocytes with TLR2, TLR4 and TLR6 on the surface, expression of TLR2 and TLR6 genes, and genes of molecules involved in the TLR signaling pathway and TLR-related NF-KB-, JNK/p38- and IRF pathways on the day of return to Earth. The observed changes displayed individual variability.

[Status of the osteoclast-activating system in cosmonauts after long-duration missions to the International Space Station].

The results of studying the system of osteoprotegerin/ receptor activator of nuclear factor kappa-B ligand (OPG/RANKL) in 22 cosmonauts after long-duration (124 to 199 days) ISS missions are presented. Immediately on return to 1 g, changes were observed in OPG and RANKL serum levels and the ability to produce unstimulated and stimulated PGA of peripheral blood mononuclear cells in vitro. Individual variability of these changes was noticed. Our findings suggest that the cytokine OPG/RANKL-system is involved in bone remodeling in members of long-duration space missions.

[Immunological aspects of a piloted mission to Mars].

The paper deals with the results of the effects of 520-day isolation and confinement modeling some elements of a mission to Mars on the immune system. Longitudinal analyses revealed that the mechanisms of adaptive response of the human immune system to the conditions of extremely long isolation led to a change of the parameters, characterizing innate and adaptive immunity. Among them the most important are: changes in the signaling PRRs--TLR, manifested in the reduction of the percentage of circulating monocytes and granulocytes expressed on its own surfaces TLR2, TLR4 and TLR6, decreases early NK cell activation potential, increases in the percentage T- and B-lymphocytes, that expressed early activation marker CD69 after adequate stimulation, and in production of cytokines in response to PHA stimulation. The active mobilization of the mechanisms of adaptive immunity, the implementation of the function of the level of immunity to a qualitatively different level, apparently, should be taken as a sign of adaptive adjustment of an organism in response to the complex influence of unfavorable factors, aimed at the preservation of immune homeostasis.

[Immune system in Russian cosmonauts after orbital space flights].

The article is an overview of the results of studies of the immune systems of cosmonauts. The use of a system approach to the evaluation of the various components of the immune system made it possible to identify a number of characteristics of adaptive change, including the quantitative and functional changes of the innate and adaptive immunity. Among them the most important are: changes in in the system of Toll like receptors (TLRs) manifested as a decrease in the content of circulating monocytes and granulocytes expressing TLR2, TLR4, and TLR6, and LPS-induced cytokine production; inhibition of the functional potential of natural killer (NK)- and T-cells. The article discusses possible factors and mechanisms of the identified changes.

[Dynamics of blood concentration of neurospecific proteins and risk of neuropathy development in the conditions of 105-day confinement].

Six male volunteers (aged 25 to 40 years) were subjects in all-round psychophysiological, hormonal and immunological studies before, in and after 105-day isolation and confinement. Blood was drawn and the 16-factorial Cattell personality inventory was filled out every 30 days. Concentrations of blood hormones, neurospecific proteins and cytokines point to a close interrelation between antibody titers to myelin-associated glycoprotein and changes in the parameters of metabolism and reproduction-related hormones, as well as cytokines and individual psychophysiology (extra-introversion, dominance, intropunitiveness, social contact selectivity, etc.), and suggest a minimum risk of demyelinizing neuropathy due to exposure to the conditions of isolation and confinement.

[Congenital human immunity during 5-day dry immersion].

The system of congenital immunity was studied in 12 essentially healthy males 18 to 26 years of age subjected to 5-day dry immersion without use of countermeasures. Peripheral blood was analyzed for monocytes, granulocytes and lymphocytes expressing the TLR2+, TLR4+, TLR6+, CD11b+, CD14+, CD16+, CD18+, CD24+, CD36+, CD54+, CD56+ and CD206+ receptors. Expression of early activation marker CD69 on lymphocytes-natural killers was studied in unstimulated and interleukin-2 activated mononuclear cell cultures. The negative shifts in the congenital immunity system in some volunteers at the end of immersion and during recovery can be considered as warnings about depletion of the system reserve and increase of the risk of infectious diseases such as caused by normal microflora which typically does not provoke pathological reactions of the host.

[Analysis of the relationships between the psychophysiological status and system of adaptive immunity in the conditions of 5-day dry immersion].

Relationships of the T- and B-components of adaptive immunity and the psychophysiological status were studied in 14 volunteers for the experiment with 5-d dry immersion (DI) w/o countermeasures. Comparison of frequency of deviations in immunity parameters of psychologically different subjects demonstrated the highest frequency in non-anxious and extravert individuals on day-5 in DI. These differences in immune reactions as a function of psychological type and temperament point to existence of a neuroimmune typology and, therefore, the necessity of concurrent immunologic and psychological investigations in order to develop separate measures of rehabilitation from and prevention of stress in people with polar psychological status.

[Indicators of innate and adaptive immunity of cosmonauts after long-term space flight to international space station].

Results of innate and adaptive immunity indicators research at 12 cosmonauts who took part in long (128-215 days) expeditions to the International space station (ISS) are presented. It is shown that a space flight can lead to deflection of deviations in human immune system. These shifts occurred in decrease of phagocytes, NK, T-lymphocytes functional activity and also in abilities of immunocompetent cells to synthesize cytokines. Significant individual changes are noted in reaction of immune system to the long term space flight conditions specifying on individual predisposition to development of immune reactance infringements in the conditions of varying gravitational influences.

[Immune system parameters of healthy humans in a chamber experiment with hyperbaric oxygen-nitrogen-argon air].

The investigation into the immune effects of 9-d exposure to elevated pressures of normoxic and hypoxic O2-N-Ar atmosphere showed changes in a number of indices of genetic and adaptive immunity in normal humans. Dynamics and depth of the functional shifts under the influence of the experimental factors appear to be connected with genetically coded mechanisms of immunoreactivity. Monitoring of immune homeostasis is basic to the prevention of immune adaptation failure.

[Human immunity system status during 7-day dry immersion].

Subpopulations of lymphocytes, activation potential of T-, B- and NK-cells as well as cytokines production by immunocompetent cells in peripheral blood were studied in five volunteers for 7-day dry immersion without use of countermeasures. Results of the investigation revealed several negative shifts in the immunity and cytokines systems instigated by the experimental conditions. The considerable variability of the immune reactions to immersion suggests individual predisposition to immunological breaks in a changed gravity environment.

[The activation processes of the immune system during low intensity exercise without relaxation].

The activation processes of T-, B- and NK-cells were studied during 8-week low intensity strength training without relaxation. After the long-term training, no changes occurred in the peripheral blood contents of the main subpopulations of immunocompetent cells (CD3+, CD4+, CD8+, CD19+ and CD16+/CD56+ lymphocytes) and serum levels of immunoglobulin A, M, and G. At the same time, training was accompanied by positive activation of the immunocompetent cells which was evident from increased percentage of CD3+, CD19+ and /CD56+ cells expressing CD69 after activation (PHA, PW and II.2, respectively). The final period of the training course was also associated with a decrease in the level of lymphocyte apoptosis and increase of proliferative responses of lymphocytes.

[Immunoglobulin e and allergen-specific IgE antibodies in cosmonauts before and after long-duration missions on the International Space Station].

Immunoglobulins (IgG, IgA, IgM, IgE), specific IgE-antibodies, and interleukin-4 (IL-4) were investigated in blood serum of nine cosmonauts before and after 128- to 195-day ISS missions. It was shown that long-duration space flight does not change significantly the content of serum immunoglobulins, allergen-specific IgE-antibodies or IL-4. Analysis for probable ratios of the total IgE and IL-4 contents in the pre- and post-flight periods did not reveal any linear correlation of these parameters.

[Modification of a method for determining the cytotoxic activity of lymphocytes--natural killers in space experiments].

A space modification of a method for determining the cytotoxic activity of natural killers (NK) uses cultures of human lymphocytes and re-inoculated suspension of tumorous myeloblasts K-562. The 3H-uridine labeled target-cells fixated in 0.1 % formalin solution proved to be best suited to the conditions prohibiting regular recharge of cultural medium and utilization of radioactive agents. The following practical conclusions were made from the space-flown experiment: pre-launch procedures (lymphocyte isolation and delivery to the launch site) and time period till dock must not be longer than 5 days (1) and during transportation to the orbiting vehicle cell cultures must be kept at 18-20 degrees C (2). The modified method can be employed to study various aspects of cell interaction such as the NK ability to destroy target-cells in suspension cultured exposed in microgravity.

[Outcome of the long-term isolation on the development of allergic reactions in humans]. / Vliianie dlitel'noi izoliatsii na formirovanie allergicheskikh reaktsii u cheloveka.

Studied were consequences of long-term isolation in airtight environment for development of the type-I (IgE-antibodies production) and type-IV (involvement of sensibilized T-lymphocytes) allergic reactions in humans. No significant changes in total IgE, specific IgE-antibodies for domestic, epidermal, fungal, grass pollen and food-borne allergens or serum IL-4 level were found in the period of the 240-d isolation with the microclimate and atmospheric parameters within their normal variations, and on completion of the experiment. Yet, after 3 mos. in isolation all subjects exhibited inhibited leukocyte migration in the presence of tuberculin. These findings bear witness to an activation of sensibilized lymphocytes known as effectors of delayed hypersensitivity.

Cell interactions in microgravity: cytotoxic effects of natural killer cells in vitro.

To study cell-to-cell interactions in microgravity we examined the functional activity of natural killer cells on board of the ISS. NK cells are the effector cells with direct cytotoxic activity to oncogenic, virus-infected cells and cells with modified differentiation. Ground-based experiments have shown that the examination of target cell lysis after incubation with NK cells is a simple and informative model for studying the influence of microgravity. NK cytotoxicity was measured as the value of non-degradeted labeled myeloblasts (K-562) after 24 hrs exposure with human lymphocytes in suspension. A special device was developed for space flight experiments. Human cultured lymphocytes and labeled K-562 cells were loaded into special syringes and delivered to the Russian segment of the ISS. Cosmonauts prepared co-cultured suspensions during the first day of microgravity, exposed them at 37 degrees C for 24 hrs and then separated H3-labeled cells on special filters. The results of ISS-8 mission showed that human NK cells in vitro remain lysis activity toward target cells in microgravity. The basal level of NK cytotoxicity was low and we did not found significant differences between "control" and "flight" values. Interferon production during the interaction between immune and target cells (ratio 10:1) in microgravity did not differ compared with ground-based control experiments. Ground exposure of the same lymphocyte samples with K-562 cells to 24 hrs clinorotation also did not lead to significant differences. These experiments paved the way for understanding the cell interaction mechanisms in space flight and the obtained results suggest that microgravity does not disrupt the interaction of NK cells with tumor cells.

[Immunologic reactivity and status of the intestinal viral flora of humans in pressurized chambers]. / Immunologicheskaia reaktivnosti' i sostoianie kishechnoi virusnoi flory chekoveka pri obitanii v germetichno zamknutykh pomeshcheniiakh.

Immunity status and intestinal viral flora were studied in 5 experiments with long-term exposure of 26 male subjects in pressurized chamber. In two experiments with congenital microclimate and gaseous environment cellular and humoral indices of immunity did not deviate from the physiological norm. None of 14 subjects in these experiments was identified as a virus-carrier. In three experiments with hard environmental conditions (elevated concentrations of ammonia and carbon dioxide) viruses were isolated from 8 out of 12 subjects. Activation of viral flora mainly occurred on a background of impaired immunologic reactivity. In two experiments carriage of virus was asymptomatic; in the third experiment with the rise of ammonia up to 7 mg/m3 two subjects developed clinic signs that could have been engendered by enteric viruses, the Coxsackie B strain specifically.