Mechanisms of Formation of Immune System Disorders in Elite Athletes (Case Study of Biathlon)
E.G. Mokeeva, associate professor, Dr.Med.
Lesgaft National State University of Physical Culture, Sport and Health, St. Petersburg
Yu.V. Yakovlev, Honored trainer of Russia
National University of Mineral Resources (Mining University), St. Petersburg
Key words: year macrocycle, elite biathletes, immunological characteristics, mechanisms of formation of immune system disorders.
Introduction. Nowadays, the need for the control over changes in the immunological characteristics of elite athletes is particularly assured, as today's training and competitive loads can have a negative effect on the immunity of athletes, thus increasing the disease incidence and reducing their performance [1, 5, 7]. Numerous studies proved that the control over the immune status of elite athletes in the process of their sports activity is an objective method of evaluation of the resistance status of the body and its level of adaptation to physical loads [4, 6].
The study of the immune system disorders and deadaptation of the body on the whole, caused by extreme training and competitive loads, has been in progress for many years now. However, these findings are systematized insufficiently as by the kinds of sport and the periods of training and competitive activity. There are few works  in which one can find the research data on the immune status of athletes involved in one specific sport throughout a particular training period and, all the more, within the whole macrocycle. Commonly, on the contrary, athletes involved in different sports are examined during the immunological studies collectively, not on a case-by-case basis, throughout different in intensity periods of competitive loads. Such an approach is unacceptable in sport, even more so in elite sport where each kind of sport and each training stage have their peculiar characteristic features.
Today we know that disorders of neuroendocrine regulation, macro- and micronutrient deficiencies, metabolic changes in the body, intoxication from the nidus of chronic infection (if there is one) provoke reduced immunological resistance at strenuous psychophysical loads . However, this problem has not been studied fully, and the details are fragmentary. For example, the response of cytokines to the load remains unclear, as well as a part of apoptosis processes and other important mechanisms of formation of immune system disorders. At the same time if knowing these mechanisms it will facilitate the development of appropriate and more physiological ways to prevent immune system disorders and immunodeficiency in athletes in the periods of strenuous loads.
The purpose of the study was to detect the mechanisms of immune system disorders in elite athletes on the example of biathlon.
Materials and methods. A total of 30 elite biathletes (aged 19-24 years) were examined in different periods of their training and competitive activity within one macrocycle. The athletes had 10 years of sports experience and followed a unified training program. The control group included 14 healthy young males of the same age who were not engaged in elite sports.
The functional activity of phagocytes was estimated with the help of the NTR test, the LC test and by phagocytosis. The phagocyte absorption capacity was assessed by the phagocytic index (PI) and phagocytic count (PC). In order to evaluate the digestive function the index of phagocytosis completeness (IPC) was determined. The level of circulating immune complexes (CIC) was determined using the method of polyethylene glycol precipitation. The immunoglobulins (Ig) of the M, G, and A classes in blood serum were detected by the conventional method of simple radial immunodiffusion. The study of the quantitative composition of the lymphocyte subpopulations was carried out by means of the flow-cytometric method. Cytokines and hormones (adrenocorticotropic hormone (ACTH), cortisol, β-endorphin, metenkephalin) in blood serum were determined using enzyme immunodetection. To rate the macro- and microelements content in the biosubstrates (blood, hair) atomic emission spectrometry and mass spectroscopy with inductively coupled plasma, as well as the microwave digestion system, were applied .
Results and discussion. The results of the research on the functional state of the phagocytic component of the immune system revealed the improvement of the absorbing and digestive capacities of phagocytes (the increase in PC and IPC) in biathletes as compared to healthy people not involved in sports (p≤0,05) within the physiological range.
According to the NTR test, the bactericidal capacity of neutrophils in athletes and individuals not doing sports did not differ and was within the physiological range, which might be evidence of the proper functioning of the oxygen-dependant antimicrobial systems of phagocytes. In turn, the activity of the oxygen-independent systems of bactericidal capacity of phagocytes in biathletes was below the physiological standard and the control group values (p≤0,05) in all the periods of the macrocycle, except for the rehabilitation period characterized by minimum intensity loads.
The levels of the high- and low-molecular CIC were significantly higher in athletes as compared to the control group.
The levels of Ig in all the classes under study were within the physiological range. Their concentration in biathletes in all the periods, except for the rehabilitation one, did not differ from that of the control group, and during the rehabilitation period was significantly higher than in individuals not doing sports.
The changes in the cellular component of the immune system in athletes under study as compared to the control group (p≤0,05) were expressed by the increase of the overall number of T-lymphocytes (CD3+) and their subpopulations - helpers/inducers (CD3+CD4+) and cytotoxic ones (CD3+CD8+), where the mean values of CD3+CD8+ exceeded the physiological standard in all the periods. Moreover, biathletes displayed an increase in the number of the activated T- and B- lymphocytes - CD3+CD25+, CD3+HLADR+, CD3+CD95+ and CD19+CD95+ in all the periods of training and competitive activity, except for CD3+CD95+ during the rehabilitation period. The levels of CD3+CD25+, CD3+CD95+ and CD19+CD95+ (except for the rehabilitation period) in athletes exceeded the physiological standard. The total number of B-lymphocytes, T-killers and true natural killer cells in biathletes did not differ from the values registered in healthy people not doing sports.
The study of the levels of cytokines in biathletes indicated the increase in the concentration of pro-inflammatory tumor necrosis factor a, interleukin 1b and anti-inflammatory interleukin 4 and interleukin 10. The values of interferon a, interferon γ and interleukin 6 did not fall outside the physiological range. By the levels of all cytokines athletes significantly differed from healthy people not involved in sports, there was registered a reducing concentration with regard to interferon a, and a rising one - with regard to the rest.
The levels of ACTH and cortisol, β-endorphin and metenkephalin in athletes significantly differed upwards as compared to non-athletes from the control group in all the training and competitive periods, except for the rehabilitation period.
The study of the macro- and microelement statuses of biathletes showed: the rise of the lead content in hair (4,5±1,1), which significantly exceeded the physiological standard, and the content of this element in blood, which almost edged the upper lower level of the physiological standard (0,018±0,001). These data are indicative of the chronic lead intoxication in biathletes resulting from their close contact with rifles. Athletes also displayed reduced levels of phosphorus, copper and manganese in blood, the rest macro- and microelements were within the physiological range. Phosphorus malnutrition may be indicative of the poor protein intake or its excessive consumption. Low blood levels of copper and manganese, probably, reflect the intensification of the functioning of antioxidant system enzymes of superoxide dismutase in terms of adaptation of lipid peroxidation in the period of strenuous training and competitive activity.
In addition, the indices of the immune status of elite biathletes were examined 1-2 hours after the one-time strenuous competitive load (50-km race).
The results of the research on the functional status of the phagocytic component of the immune system revealed the deterioration of the phagocyte absorption and digestive capacities in biathletes after the race as compared both to healthy people from the control group not engaged in sports, and to the similar indices displayed by these athletes in the season. According to the NTR and LC tests, the indices of the bactericidal capacity of neutrophils were lower than those of the control group and biathletes in the season.
The levels of the high- and low-molecular CIC were significantly higher in biathletes after the race as compared to the control group and had a tendency to the increase compared with the levels of the high- and low-molecular CIC in biathletes in the season.
The results of the research on the cellular component of the immune system in biathletes after the race showed significant reduction of CD19+ and the increase in CD19+95+ in comparison with the control group and the season values registered in the same athletes. Moreover, there was observed a tendency to the increase in CD3+CD4+ and CD3+95+ in individuals not doing sports, as well as in biathletes in the season. The rest indices of the cellular component of the immune system under study – CD3+, CD3+CD8+, CD3+CD25+, CD3+HLADR+, CD95+, CD3+16+56+, CD3-16+56+, CD3-8+ had close values with similar indices in biathletes during training and competitive loads of the macrocycle.
Conclusion. The complex dynamic study of the immune status of elite biathletes has revealed changes in the athletes' immunological characteristics during training and competitive activities within a macrocycle, and their nature and severity depending on the period of training. In the period of the most strenuous psychophysical loads of the year macrocycle immune dysfunctions are formed in biathletes, and they are expressed by the decrease in the bactericidal capacity of phagocytes, the increase in the level of the low-molecular CIC, the rise of cytotoxic T-lymphocytes and activated T- and B-lymphocytes - CD3+25+, CD3+95+, CD19+95+, that can be considered as incipient signs of general deadaptation of athletes' bodies. One-time strenuous competitive load in terms of training and competitive macrocycle results in the intensification of immune disorders and apoptosis processes in biathletes.
Basing on the analysis of the research findings in the sphere of sports immunology (according to the literature data) as well as our studies, the main mechanisms of formation of immune system disorders in elite athletes were determined. They are:
- neuroendocrine and cytokine regulation disorders, proved by our research on the excessive activation of stress-releasing pituitary-adrenocortical axis (ACTH, cortisol), and the increase in the number of pro-inflammatory cytokines (TNF-a, IL-1b). In addition, a response compensatory increase in the functioning of stress-limiting system of opioid peptide (β-endorphin, metenkephalin) and increase in the number of anti-inflammatory cytokines (IL-4, IL-10);
- intensification of apoptosis processes, which are emphasized by the significant rise of the cells on which CD 95 (CD95+, CD3+95+, CD19+95+) are expressed;
- lack of immuno-significant macro- and micronutrients, and as a result deterioration of the energy and plastic provision of the immune system and the body on the whole .
In addition, the characteristic immunosuppressive factor in biathletes appears to be the chronic lead intoxication.
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