Effects of intensified training and taper on immune function

Although resting immune function is not very different in athletes compared with non-athletes periods of intensified training (overreaching) in already well trained athletes can result in a depression of immunity in the resting state. Illness-prone athletes appear to have an altered cytokine response to antigen stimulation and exercise. Having low levels of salivary IgA secretion also makes athletes more susceptible to upper respiratory tract infections. Overtraining is associated with recurrent infections and immunodepression is common, but immune functions do not seem to be reliable markers of impending overtraining. There are several possible causes of the diminution of immune function associated with periods of heavy training. One mechanism may simply be the cumulative effects of repeated bouts of intense exercise (with or without tissue damage) with the consequent elevation of stress hormones, particularly glucocorticoids such as cortisol, causing temporary inhibition of TH-1 cytokines with a relative dampening of the cell-mediated response. When exercise is repeated frequently there may not be sufficient time for the immune system to recover fully. Tapering has been described as a gradual reduction in the training load which allows the recovery of physiological capacities that were impaired by previous intensive training and permits further training-induced adaptations to occur accompanied by competition performance enhancements. The majority of the studies that have examined the recovery of immunoendocrine responses during 1-3 week tapers in trained athletes have mainly reported enhanced performance, often accompanied by increased anabolic activity, reduced physiological stress and restoration of mucosal immunity and immune function.

Quando se compara a função imune, em repouso, de atletas e não atletas, não se verificam grandes diferenças. Porém, períodos de treinamento intensificado ("overreaching") em atletas bem treinados podem induzir supressão da imunidade no estado de repouso. Os atletas com maior propensão para contrair doenças parecem apresentar uma resposta alterada de citocinas, tanto quando estas são estimuladas por antígenos, quanto em resposta ao exercício propriamente dito. Baixos níveis de secreção de IgA salivar também contribuem para tornar os atletas mais susceptíveis à infecções do trato respiratório superior. A síndrome do "overtraining" é associada a infecções recorrentes e a imunossupressão é comum; no entanto, marcadores da função imune não parecem ser suficientemente sensíveis ao "overtraining" eminente. Existem várias possíveis causas para a diminuição da função imune associadas com períodos de treinamento severo. Um possível mecanismo pode ser simplesmente, o efeito acumulativo de atividades e sessões repetidas de exercício intenso (com ou sem dano tecidual), com a consequente elevação dos hormônios de estresse, particularmente os glicocorticóides como o cortisol, causando assim, uma inibição temporária das citocinas de TH-1, com uma relativa atenuação da resposta imune celular. Quando o exercício é repetido frequentemente, pode não haver tempo suficiente para uma total recuperação do sistema imunológico. O "Tapering" tem sido descrito como uma gradual redução na carga de treinamento a qual permite a recuperação das capacidades fisiológicas, que por sua vez, foram afetadas pelo treinamento intensivo anterior, permitindo assim, que adaptações adicionais decorrentes do treinamento ocorram, acompanhadas pelo incremento do desempenho competitivo. A maioria dos estudos que investigaram a recuperação das respostas imuno-endócrinas em atletas durante uma a três semanas de "taper" tem registrado aumento do desempenho, frequentemente...

Effect of continuous darkness on immune response [in vivo assay]

Reports denote that changes in day length enhance or suppress components of immune function in several mammalian species. The aim of the present experimental study is directed to test the hypothesis dealing with the effect of photoperiods on some immune limbs responsiveness. Twenty six male and female BALB/C mice, 5-7 weeks old, 14-18gm weight divided into two groups, test groups [n=8 mice for each sex] and control groups [n =5 for each sex]. Test groups were kept in a dark room for a month, while control groups were kept in a room where the photoperiod was day light: darkness 12:12hr. All studied groups immunized with 0.2ml [10% sheep red blood cells] on day 4 and 8 of the last 12 days of the experiment. The weights of all animals were measured at the beginning and the end of the experiment. Arthus reaction, delayed type hypersensitivity and serum antibody titer were assessed on day 11 and 12 of program. Significant increase [P<0.005] in body weight, index level of Arthus reaction, delayed type hypersensitivity and serum antibody titer in the test groups in comparison with the control groups were found. Data are consistent with the hypothesis that immune parameters are enhanced in short photoperiods or continuous darkness

[Allostimulatory efficiency of splenic dendritic cells from pregnant and non pregnant mice]

Mammalian reproduction looks like an immunological paradox, because fetal alloantigens encoded by father genes should induce cell mediated immune responses leading to fetal loss. Maternal immune system, in addition to local modulation, undergoes systemic modulations during pregnancy. Dendritic cells [DCs], as professional antigen presenting cells, play a key role in initiation and control of immune response and it seems that functional changes in these cells during pregnancy may contribute to the systemic immune tolerance. To address this issue, in this study we isolated and purified DCs from pregnant mice and evaluated their stimulatory potential to induce proliferative response of allogenic T cells in unidirectional mixed leukocyte reaction [MLR]. Following collagenase digestion of splenic tissue, using density gradient centrifugation [13% Nycodenz] and adherence properties of DCs to the bottom of tissue culture dish, 7x10[5] DCs were isolated from each spleen with more than 95 percent purity. Allogenic T cells were isolated by nylon wool column, using their non-adhesive character to nylon wool. After radiation, isolated dendritic cells from pregnant and non-pregnant Balb/c mice were used in mixed leukocyte culture with C57BL/6 mice T lymphocytes. T lymphocyte proliferation was measured after 72 hours by [3]H- thymidine incorporation. 7x 10[5] dendritic cells with the purity of >95% were isolated from each spleen. Also the yield of T- lymphocyte form Inguinal and Brachial lymph nodes was about 3-5x10[5] with the purity of%85-90. The results showed that there is no statistical difference between stimulatory potential of DCs form pregnant [cpm=33000] and non- pregnant [cpm=35000] mice in induction of allogenic T-Cell proliferation. These findings can result from low concentration of immune suppressor factors in circulatory system of pregnant mice or due to separation of dendritic cells from pregnancy microenvironment and their maturity in vitro in the absence of the immune suppressor factors