Hematological reactions in the inhabitants of the Arctic on a polar night and a polar day

Abstract Purpose The purpose of this study is to identify the features of hematological reactions in the inhabitants of the Arctic territory of the Kola Peninsula on a polar night and a polar day. Methods The study included determining the hemogram, neutrograms, monocytograms, lymphocytograms, and phagocytic activity neutrophil granulocytes, enzyme immunoassay, flow cytometry. Results It was established that during the polar night, there is an increase in the activity of migration of leukocytes from the marginal pool to the circulating pool, an increase in the intensity of phagocytosis by neutrophils, an increase in the concentrations of noradrenaline, cortisol, as well as an increase in hyperergic reactions involving immunoglobulin E and inhibitory processes due to an increase in interleukin‐10. Conclusion A prolonged lack of sunlight causes a decrease in the reserve capacity for regulating homeostasis and forces the body to use proliferative reactions, which is reflected in the increase in stab neutrophils, large lymphocytes in the structure of the lymphocytogram and CD10+ lymphocytes. In winters, the frequency of neutropenia registration also increases to 13% of cases, the deficit of phagocytic activity of neutrophils; lymphopenia is recorded in 20% with T‐helper deficiency (37%). A part of the population probably has a relatively high degree of vulnerability to the action of natural environmental factors and is not able to completely restore the initial levels of the effectiveness of adaptation reactions in the summer. So at the end of the polar day in 8% of adults born in the north, neutropenia is recorded and in 21%—lymphopenia.

end of the polar day in 8% of adults born in the north, neutropenia is recorded and in 21%-lymphopenia.

| INTRODUCTION
Photoperiods are the most stable and independent of human activity rhythms. 1 The intensity of solar radiation and its spectral composition depends on solar activity, the height of the sun above the horizon, the mass of the atmosphere, and the presence of clouds. 2 In the North, the annual total arrival of solar radiation is two times lower than that in the middle zone of the Russian Federation (112.71, respectively, and amounts to 299.59 kJ/cm 2 per year). Its maximum level is reached in July (from 30.58 to 59.92 kJ/cm 2 ) and the minimum falls on December (0.42 kJ/cm 2 ). In the period from October to February, the negative radiation balance is on average 3.35 kJ/cm 2 . During this period, the low standing of the sun and the short duration of its radiance are noted; the largest-in July (334 hours), the smallest-in December and is only 1 hour. The period of absence of the influence of solar radiation is defined as biological darkness. 3 A negative factor affecting the health of the inhabitants of the European North is the shortage of ultraviolet radiation. This territory is assigned to the zone with a significant deficit of the biologically active part of the solar spectrum of ultraviolet radiation. The circumpolar regions belong to the zone of prolonged insufficiency of ultraviolet radiation, which begins in October, and from the middle of November into the polar night, a period of biological darkness sets in. After the end of the polar night, the lack of ultraviolet radiation persists until April. It is known that infrared radiation is one of the most constant environmental factors continuously acting on the human body. The human body continuously absorbs and itself emits infrared rays; this heat transfer can vary significantly depending on the temperature of the human body and the environment. Solar activity has a direct effect on the biological rhythms of all physiological functions. [4][5][6] The influence of a change in photoperiodicity on the state of peripheral blood according to the literature is ambiguous. The most thoroughly studied is the change in the state of the erythron system. [7][8][9][10] There is evidence of an increase in the phagocytic activity of neutrophilic granulocytes in winters among residents of the middle zone of the Russian Federation. 11 Deficiency of solar insolation is associated with a decrease in the activity of various enzyme systems, which causes changes in the mechanisms of regulation of the activity of metabolic processes and tissue respiration. [12][13][14][15] The influence of sunlight on hemodynamics and the cardiovascular system is especially great. [16][17][18][19][20][21] During the polar night, diastolic pressure rises. 22,23 When analyzing the phase structure of the cardiac cycle, 12.5% of patients examined during this period revealed myocardial hypodynamia syndrome and 25% showed an elongated isometric contraction phase. 24 During this period, the minute volume of blood decreases, 24,25 the pulse can slow down, 22,[25][26][27][28] and the blood flow velocity decreases. 25 In arterial blood, oxygen saturation does not differ from those in individuals living at the mid-latitude level. 29,30 But the arteriovenous difference in oxygen significantly exceeds the norm, which indicates an increase in oxygen consumption 31 and an increase in carbon dioxide in venous blood. 10,32 In winters, the blood content of residents of the Arctic territories is higher in cortisol. 23,29,[33][34][35] The period of the polar day is characterized by a predominance of the tone of the sympathetic part of the autonomic nervous system, in winters, there is a gradual transition to parasympathetic reactions. 22,33,36 So, photoperiodicity-a change in the level of illumination-determines the chronobiological regulation of the functional activity of various body systems. The daily influence of solar insolation factors or their deficiency, as well as the long-term repetition of such stressful situations, can cause a decrease in the effectiveness of regulatory mechanisms. Peripheral blood reactions to extreme factors appear first and quite objectively warn of possible stresses in regulatory mechanisms. Earlier, we established seasonal fluctuations in hemograms and parameters of the immune background in people born and permanently living in the Arctic in the Nenets Autonomous district and the Arkhangelsk region. It has been established that on a polar night, the frequency of detection of neutropenia, deficiency of phagocytic defence, the content of mature T-lymphocytes and secretory immunoglobulin A (IgA) in the peripheral blood of the examined people increases. 37,38 In previous studies, it was found that people living in the Arctic Kola Peninsula showed signs of inhibition of switching immunoglobulin M (IgM) synthesis to immunoglobulin G, which significantly weakens the protective function of antibodies in tissues. 39 The immune status is characterized by signs of a decrease in the reserve capacity for homeostasis regulation, which is manifested by a decrease in the activity of lymphocyte proliferation against the background of less significant concentrations of natural glycoproteins when compared with residents of the Nenets Autonomous Okrug. 40 This study presents the results of a comparative study of hemograms and immune status in residents of the polar region of the Murmansk region.
The Revda settlement of (67°56′ 13″ middle latitude) and Lovozero village of (68°02′ 00″ middle latitude) Lovozersky district of the Murmansk region of the Russian Federation are located beyond the Arctic Circle in the central part of the Kola Peninsula. It is known that this territory belongs to a very unfavorable zone with intense environmental and climatic conditions affecting people and critical stress of adaptation systems, 41 and according to living conditions-to an extremely uncomfortable zone. 42,43 Biological twilight and polar night, when a negative radiation balance is recorded, last from October to February; polar night lasts 25 days from 10 December to 3 January; the polar day lasts 52 days from 27 May to 17 July.
The problem of human adaptation to a pronounced change in the photoperiod is determined by a change in physiological reactions, including the endocrine and immune systems. But the issue of ensuring adaptation to contrast photoperiodic in extreme situations remains unresolved. In this regard, the aim of the study is to identify the features of hematological reactions in the inhabitants of the Kola Peninsula on a polar night and a polar day.

| MATERIALS AND METHODS
The object of study were the inhabitants of the Arctic territory, aged 21-to 60-years old, living in the Arctic Revda settlement and village Lovozero, Lovozero district, Murmansk region of the Russian Federation. The study includes the results of a survey of 249 healthy people: 131 people were examined during the polar night and 118 people on a polar day.
All studies were conducted with the consent of the volunteers and in accordance with the requirements of the Helsinki Declaration of the World Medical Association. Ethical principles for conducting medical research involving a person as a subject (1964, as amended and supplemented from 2013).
For the study, peripheral venous blood was taken from the ulnar vein in the morning on an empty stomach. The number of cells of the leukogram, monocytogram, lymphocytogram, and neutrogram were counted in blood smears stained by the Romanovsky-Giemsa method; monocytogram was determined by the method of Grigorova (1956), lymphocytogram-according to the method of Kassirsky (1970), neutrogram-according to the method of Todorov (1968). The phagocytic activity of neutrophils was studied using the test kit from Reacomplex (Chita, Russia). Isolation of mononuclear cells from peripheral blood was performed according to the method of Boymn (1976), phenotyping of lymphocytes in an indirect immunoperoxidase reaction using monoclonal antibodies (MedBioSpektr; Sorbent, Moscow, Russia), and flow cytometry using an Epics XL apparatus from Beckman Coulter with Immunotech a Beckman Coulter Company reagents (France).
In blood serum by the solid-phase method, enzymelinked immunosorbent assay on an automatic enzymelinked immunosorbent analyzer Evolis (Bio-Rad, Germany) with the appropriate reagents determined the content of cytokine interleukin-10 (IL-10; Seramnum Diagnostica, Germany), noradrenaline (IBL, Germany), and cortisol (DBC, Canada). The concentration of circulating immune complexes (CIK) was determined by the standard precipitation method using 3.5%, 4.0%, and 7.5% PEG-6000 in blood serum. The reaction was evaluated on Evolis.
Statistical processing of the obtained data was carried out using the Statistica 10.0 software package (StatSoft) with a determination of average values and presented as the arithmetic mean ± error of the mean (M ± m), the significance of differences was evaluated using Student's t test. The results of nonparametric processing methods are presented as the median (Me) and interquartile range in the form of 25 and 75 percentiles. The statistical significance of the differences was determined using the nonparametric Mann-Whitney test. The critical level of significance (P) in the study was taken equal to .05.
People were examined on 3 to 5 December and 18 to 20 June, that is, during periods of maximum severity of the polar night and the greatest duration of the polar day. Neutrophilic leukocytosis was detected with a neutrophilic granulocyte count more than 5.5 × 10 9 cells/L, a neutrophilic granulocyte count deficit (neutropenia) less than 2.0 × 10 9 cells/L, lymphocytosis more than 3.0 × 10 9 cells/L, lymphopenia less than 1.5 × 10 9 cells/L and monocytosis-0.6 or more × 10 9 cells/L.

| RESULTS AND DISCUSSION
During the polar night, the frequency of registration of increased concentrations of circulating neutrophilic granulocytes is higher (22.90% ± 0.36% and 2.63% ± 0.42% of the subjects, respectively, Figure 1). This neutrophilic BALASHOVA ET AL.
| 417 leukocytosis is accompanied by a "left shift" of 60.00% ± 2.57% with an increase in the concentration of stab neutrophilic granulocytes (from 0.43 ± 0.12 to 0.70 ± 0.13 × 10 9 cells/L; P = .028). Activation of the proliferation of neutrophilic granulocytes is accompanied by an increase in their apoptosis activity with an increase in the composition of cells with five or more nuclear segments (0.03 ± 0.01 and 0.29 ± 0.07 × 10 9 cells/L, respectively; P = .003).
Along with an increase in the concentration of circulating neutrophilic granulocytes in winters, neutropenia was detected in 12.98% ± 0.27% of the examined individuals; during the polar day, neutropenia is set at 7.89% ± 0.73%. In cases of neutropenia, a deficit of phagocytic activity of these cells was recorded; the frequency of registration of a deficit of phagocytic protection in winter was noticeably higher than in summer (45.05% ± 0.51% and 36.84% ± 1.40%, respectively).
In winters, the rate of monocytosis is higher than in summers (45.04% ± 0.51% and 21.05% ± 1.20%, respectively). The increase in the concentration of circulating monocytes is mainly provided by the redistribution from the marginal to the circulating pool due to mature monocytes (0.59 ± 0.08 and 0.18 ± 0.02 × 10 9 cells/L, respectively; P < .001) without signs of proliferative activity according to the analysis of monocytograms. One of the most important functions of monocytes in the phagocytosis of immune complexes circulating in the bloodstream by receptor endocytosis. 44 But despite the increase in the blood monocyte content in the winter, the frequency of registration of elevated concentrations of CIK is much higher than on a polar day: CIK IgA 60.26% ± 0.59%, CIK IgA 75.64% ± 0.66%; on a polar day, 27.03% ± 1.36% and 48.65% ± 1.83%, respectively. Even in the average results, the concentrations of CIK in the blood during the polar night were significantly higher (CIK IgA and IgM: 4.48 ± 0.29 and 5.41 ± 0.31 g/L vs 2.56 ± 0.30 and 3.59 ± 0.45 g/L; P < .001).
Quite often, lymphopenia was recorded at practically the same level both in winters and summers (19.85% ± 0.34% and 21.05% ± 1.20%); the detection rate of lymphocytosis during the polar night was 1.5 times higher (29.01% ± 0.41% and 18.42% ± 1.12%; Figure 2). There is reason to believe that lymphocytosis on a polar night is ensured by lymphoproliferation, since the content of large lymphocytes in the lymphocytogram is much higher even in average results (0.33 ± 0.04 vs 0.14 ± 0.02 × 10 9 cells/L; P < .001). Signs of increased proliferative activity of lymphocytes with an increase in the content of CD10+ phenotype in the peripheral blood, potentially capable of proliferation, were detected in winters at 35.92% ± 0.46% and 37.50% ± 1.60% in summers. During the polar night, an increase in the content of CD8+ cytotoxic phenotypes was recorded at 37.50% ± 0.47%; in cases of lymphocytosis, increased concentrations of CD8+ were found at 84.38% ± 3.52%. Against the background of increased activity of cell-mediated cytotoxicity, a very high level of deficiency of T-helper cells was established in winter and summer periods (37.50% ± 0.47% and 37.04% ± 1.59%).
So, during the polar night, the content of neutrophilic leukocytes (22.90% ± 0.36%), monocytes (45.04% ± 0.51%), and lymphocytes (29.01% ± 0.41%) circulating in venous blood is higher. The increase in white blood cell count is due to the activation of proliferative processes of the corresponding cell sprouts.
An increase in the content of neutrophilic granulocytes is not accompanied by an increase in % of active phagocytes, the intensity of phagocytosis in terms of the F I G U R E 1 Neutrophilic leukocytosis. Peripheral venous blood. Coloring according to Romanovsky-Giemsa. ×1000. 1, 2, 3, 4: neutrophilic white blood cells, 5: monocyte F I G U R E 2 Lymphocytosis. Peripheral venous blood. Coloring according to Romanovsky-Giemsa. ×1000 phagocytic number increases (5.51 ± 0.11 vs 3.92 ± 0.14 units/cell; P < .001). In winters, the frequency of neutropenia registration also increases (from 7.89% ± 0.73% to 12.98% ± 0.27%) and the deficit of phagocytic activity of neutrophils from 36.84% ± 1.40% to 45.05% ± 0.51% in these cases. It is known that neutrophilic granulocytes, making up the bulk of circulating leukocytes, not only phagocytize, are antigen-reactive cells, perform antibodydependent cytolysis of affected, transformed and old cells, and are sources of a huge number of primary and secondary mediators of inflammatory reactions and all known cytokines. [45][46][47][48] Deficiency of the content of these cells creates serious problems in the regulation and provision of almost all adaptive reactions.
Along with lymphocytosis during the polar night, the incidence of lymphopenia increases. Given the role of lymphocytes in the implementation of immune responses, the high prevalence of T-helper deficiency, reaching 30% to 37%, we can say with alarm about the risk of the formation of secondary environmentally dependent immunodeficiency in a person living in the Arctic. It is possible that a certain contribution to this is made by factors associated with a lack of sunlight. In the North, from October to February, the sun is low and its duration is short; the highest is in July (334 hours), the lowest is in December and is only 1 hour. The period of absence of the influence of solar radiation is defined as biological darkness. 3 Adverse climatic factors include the lack of total solar radiation. The total radiation in the North in September is two times, and in October, five times less than in the middle zone of the Russian Federation, and in the next four months (November-February), there is practically no natural radiation of the sun in the north. A negative factor affecting the health of the inhabitants of the European North is the shortage of ultraviolet radiation.
Reactions with a change in the concentration of circulating leukocytes are provided primarily by changes in hemodynamics. It is known that a dynamic equilibrium is established between circulating and parietal cells, which is constantly shifting toward an increase or decrease in both its components. 49 Migration and perfusion of cells are provided by a significant slowdown in blood flow in the capillary network of the bloodstream. In this case, it becomes possible for the cell to adhere to the capillary wall with its subsequent exit beyond the vascular bed. [50][51][52] Changing the ratio of circulating and parietal pools are the main signal for a hemodynamic reaction. The microvasculature is a system of transport blood flow, its functional state varies depending on the state of the tissues provided by the blood in this section of the blood flow. [53][54][55][56][57][58][59][60] The functional state of the microvasculature is ensured by numerous regulatory mechanisms: endothelial origin with the secretion of nitric oxide and vasoconstrictor endothelin-1, neurogenic sympathetic activity. 61 Hemodynamic reactions are provided by catecholamines and prolonged by cortisol. [62][63][64] Indeed, during the polar night, in individuals with a deficiency of neutrophilic granulocyte and lymphocyte counts, an increased content of noradrenalin (10.92% ± 0.25% and 0.85% ± 0.08%) and cortisol (20.00% ± 0.34% and 9.53 ± 0.26%), respectively. Violation of the ratio of catecholamines and cortisol causes imperfection of regulatory mechanisms and is characteristic of a state of readiness for stress, a state of allostasis. The immunosuppressive properties of cortisol are widely known. 65 There is also a tendency to increase the content of this hormone in the inhabitants of the northern territories. 23,29,33,34 A relatively constant increase in the content of cortisol causes the formation of an immunodeficiency state. Among persons with deficiency of T-helpers, the frequency of recording high concentrations of cortisol in the blood is markedly higher (85.71% ± 3.57%). It is known that the content of IL-10 is associated with immunosuppression and increases in chronic pathology. [66][67][68][69] Activation of IL-10 production can be initiated by an increase in blood catecholamines by suppressing the functional activity of T-helpers and their production of pro-inflammatory cytokines such as interferon-γ, tumor necrosis factor-α, and IL-12. 70 In such immunosuppression conditions, it is justified to activate an alternative class of immunoglobulin E (IgE), which enhances the effectiveness of immune defence by involving the powerful cytolytic potential of eosinophils and basophils. Indeed, with a low level of light mode, the immune response in Arctic residents is accompanied by increased concentrations of IgE (25.57% ± 0.38% and 16.36% ± 0.34%) and IL-10 in the blood (10.23% ± 0.24% and 2.04% ± 0.12%).

| CONCLUSION
It seems that only those who have a certain adaptive reserve can fully adapt to the sharply changed polar night and polar day. The increased need for leukocytes in tissues in conditions of deficiency of sunlight can be compensated by an increase in the metabolic activity of leukocytes (increased activity of leukocyte migration from the marginal pool, the intensity of phagocytosis by neutrophils), a change in the hemodynamics of the microvasculature by catecholamines and the release of cells from the depot. Long-term exposure to the factor leads to a reduction in the reserve capacity for regulating homeostasis and forces the body to use proliferative reactions.
A part of the population probably has a relatively high degree of vulnerability to the action of natural environmental factors and is not able to completely restore the initial levels of the effectiveness of adaptation reactions in the summer. So at the end of the polar day in 8% of adults born in the north, neutropenia is recorded and in 21%-lymphopenia.
Hyperergic reactions involving IgE and inhibitory processes due to IL-10 are, in our opinion, the criteria for an unfavorable state of adaptive mechanisms. Elevated concentrations of IgE during the polar night are found in 26% in individuals who have no history of allergy; in summer, the frequency of their registration decreases to 16%. IL-10 inhibition was detected in December at 10%, and in summer at 2%.