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Effect of Exercise Intensity on Cell-Mediated Immunity

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Effect of Exercise Intensity on Cell-Mediated Immunity sports Perspective Effect of Exercise Intensity on Cell-Mediated Immunity Katsuhiko Suzuki 1,* and Harumi Hayashida 2 1 Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa 359-1192, Japan 2 Faculty of Culture and Sport Policy, Toin University of Yokohama, 1614 Kurogane-cho, Aoba-ku, Yokohama 225-8503, Japan; [email protected] * Correspondence: [email protected]; Tel.: +81-4-2947-6898 Abstract: Moderate-intensity exercise is considered to enhance immune function and to be useful for preventing acute upper respiratory infections and similar conditions. Many people practice low- intensity short-duration exercise with the expectation of a beneficial effect on immunocompetency. However, it is difficult to affirm the existence of definite evidence of such a benefit. In this article, we discuss the effects of low-intensity short-duration exercise on cell-mediated immunity, and contrast them to the effects of high-intensity and long-duration exercise. Whereas high-intensity exercise induces inflammation and reduces cell-mediated immune system function, low-intensity exercise does not appear to have a large effect on either inflammation or cell-mediated immune function. Low-intensity exercises such as walking and yoga, which are helpful to relieve stress, cannot be considered as harmful to the immune system. Although yoga was shown to impose fewer restrictions on breathing and physical strain, the evidence that yoga enhances cell-mediated immunity remains insufficient. Therefore, further studies are needed to examine the exercise mode that may be most effective for improvement of immune functions. Keywords: exercise; walking; yoga; cellular immune system; cytokines; inflammation 1. Introduction It is well known that exercise promotes cell-mediated immune system function by Citation: Suzuki, K.; Hayashida, H. releasing anti-inflammatory cytokines (IL-4, IL-1ra, IL-5) at the site of injuries [1]. Further, Effect of Exercise Intensity on exercise intensity and duration have been demonstrated to have a great impact on immune Cell-Mediated Immunity. Sports 2021, 9, 8. https://doi.org/10.3390/ system function [2–6]. This beneficial effect of exercise is due to the anti-inflammatory ef- sports9010008 fects of exercise mediated by the downregulation of Toll-like receptors and/or cytokines [6]. Exercise intensity is defined as the amount of energy expended per unit of time due Received: 26 October 2020 to the exercise performed. Moderate-intensity exercise is considered to enhance immune Accepted: 6 January 2021 function and to prevent acute upper respiratory infections and similar conditions [7,8]. Published: 11 January 2021 Excessive amounts of prolonged high-intensity exercise may cause a downregulation of immune function. Low-intensity exercise is good for the beginner or individuals who Publisher’s Note: MDPI stays neu- have chronic health issues. According to a health survey conducted in the USA, 51% of tral with regard to jurisdictional clai- respondents practiced yoga as a low-intensity short-duration exercise, and although 50% ms in published maps and institutio- of respondents claimed a beneficial effect on the immune system as a reason to practice nal affiliations. yoga [9], it is difficult to affirm the existence of definite evidence at this point from recent reviews [9,10]. Some other examples of low-intensity exercise are light walking, stretching or swimming at a slow and steady pace. Low-intensity short-duration exercise may have a beneficial effect on cell-mediated immune system function [3,8]. In this review paper, Copyright: © 2021 by the authors. Li- we discuss the effects of cytokine dynamics that result from low-intensity short-duration censee MDPI, Basel, Switzerland. This article is an open access article exercises on cell-mediated immunity, in contrast to the effects of high-intensity and long- distributed under the terms and con- duration exercise. ditions of the Creative Commons At- 2. Function and Control Mechanism of Cell-Mediated Immunity tribution (CC BY) license (https:// creativecommons.org/licenses/by/ Immunity is a host defense function that aims to prevent abnormal cells such as 4.0/). tumor cells and foreign microorganisms from invading the body, and involves actions Sports 2021, 9, 8. https://doi.org/10.3390/sports9010008 https://www.mdpi.com/journal/sports Sports 2021, 9, x 2 of 7 2. Function and Control Mechanism of Cell-Mediated Immunity Sports 2021, 9, 8 Immunity is a host defense function that aims to prevent abnormal cells such as tu-2 of 7 mor cells and foreign microorganisms from invading the body, and involves actions from several types of immune cells. Cell-mediated immunity refers to the elimination mecha- nisms of tumor cells and intracellular pathogens, including viruses, by the functions of immunefrom severalcells, mainly types comprising of immune cells.T cells, Cell-mediated macrophages immunityand natural refers killer to (NK) the elimination cells. In mechanisms of tumor cells and intracellular pathogens, including viruses, by the functions the broader sense, the defense mechanisms mediated by other immune cells such as neu- of immune cells, mainly comprising T cells, macrophages and natural killer (NK) cells. trophils can be included in the definition of cell-mediated immunity, since multiple im- In the broader sense, the defense mechanisms mediated by other immune cells such as mune cells exert similar effects owing to the shared bioactive substances (cytokines) that neutrophils can be included in the definition of cell-mediated immunity, since multiple control these immune cells. immune cells exert similar effects owing to the shared bioactive substances (cytokines) that Helper T (Th) cells, which play a central role in cell-mediated immunity, are induced control these immune cells. to differentiate into type 1 helper T (Th1) cells by interleukin (IL)-12, which then activates Helper T (Th) cells, which play a central role in cell-mediated immunity, are induced cytotoxic T (Tc) cells, macrophages and NK cells via immunomodulatory cytokines such to differentiate into type 1 helper T (Th1) cells by interleukin (IL)-12, which then activates as IL-2 and interferon-gamma (IFN-γ) [11]. In contrast, type 2 helper T (Th2) cells are in- cytotoxic T (Tc) cells, macrophages and NK cells via immunomodulatory cytokines such duced to differentiate by the anti-inflammatory cytokine IL-4 and produce IL-10 with as IL-2 and interferon-gamma (IFN-γ)[11]. In contrast, type 2 helper T (Th2) cells are strong immunosuppressive effects. This, in turn, suppresses cell-mediated immunity Th1 induced to differentiate by the anti-inflammatory cytokine IL-4 and produce IL-10 with strong cells,immunosuppressive which includes those effects. which This, result in in turn, immune suppresses suppression cell-mediated or the elimination immunity Th1of un- cells, necessarywhich includes immune those and whichinflammatory result in immuneresponses suppression after removal or the of eliminationforeign bodies of unnecessary (Figure 1). immune and inflammatory responses after removal of foreign bodies (Figure1). FigureFigure 1. Th1/Th2 1. Th1/Th2 cytokine cytokine balance balance and immune and immune respon responses.ses. Modified Modified from Suzuki, from Suzuki, K., Exercise K., Exercise Immunol.Immunol. Rev. Rev. 8: 6–48, 8: 6–48, 2002 2002 [11]. [11 ]. IL-12IL-12 is also is also known known as a as NK a NK cell-activating cell-activating factor, factor, which which has has two two subunits, subunits, p35 p35 and and p40;p40; p35 p35 exists exists as a asp70 a dimer p70 dimer and activates and activates both NK both cells NK and cells Th1 and cells Th1 [11,12]. cells [The11,12 IL-12]. The p40IL-12 subunit p40 has subunit 200-fold has lower 200-fold activity lower compared activity compared to that of p70 to that and of is p70considered and is considered to have an toinhibitory have an effect inhibitory to IL-12 effect p70 to [13]. IL-12 IL-12 p70 [p4013]. has IL-12 a similar p40 has structure a similar to structure that of pro-in- to that of flammatorypro-inflammatory cytokines cytokines such as IL-6 such to as induce IL-6 to inflammation induce inflammation [12–14]. Therefore, [12–14]. Therefore, cell-medi- cell- atedmediated immunity immunity is regulated is regulated by a complex by a complex mechanism mechanism in connection in connection to inflammation to inflammation (Fig- ure(Figure 1). 1). 3. Effects3. Effects of High-Intensity of High-Intensity and and Long Long Duration Duration Exercise Exercise on onImmune Immune Variables Variables ReportsReports demonstrate demonstrate the the effects effects of of relatively relatively high-intensity high-intensity exercise exercise and long-durationlong-dura- tionactivities, activities, such such as as marathonmarathon running, on on immune immune function function [15,16]. [15,16 ].They They state state that that im- im- munemune function, function, which which includes includes cell-mediated cell-mediated immunity, immunity, is suppressed is suppressed for a forfew a hours few hours to a fewto adays few after days such after high-intensity such high-intensity exercise exercise and leads and to leadsincreased to increased susceptibility susceptibility to infec- to tionsinfections [15–19]. [Cell-mediated15–19]. Cell-mediated immunity immunity is evaluated is evaluated in vivo byin a vivodelayed-onsetby a delayed-onset hypersen- hy- sitivitypersensitivity reaction after reaction vaccination, after vaccination, in which one in study which demonstrated one study demonstrated decreased hypersen- decreased sitivityhypersensitivity after exhaustive after endu exhaustiverance exercise endurance [17]. exerciseAlthough [17 moderate-intensity]. Although moderate-intensity exercise is exercise is generally considered to activate immune functions given a temporary elevation generally considered to activate immune functions given a temporary elevation in NK cell in NK cell activity, which then returns to the pre-exercise state after the exercise, NK cell activity, which then returns to the pre-exercise state after the exercise, NK cell activity is activity is suppressed for several hours after high-intensity exercise [20].
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