Studying the impact of nutritional immunology underlying the modulation of immune responses by nutritional compounds – a review

Abstract

Nutritional immunology perception is a condition in which an altered supply of nutrients modifies immune response, and it has become linked intimately with endeavors to improve the clinical patients who often require an exogenous supply of nutrients. Scientists have revealed narrative mechanisms by which naturally occurring compounds such as abscisic acid, conjugated linoleic acid, n-3 poly-unsaturated fatty acids and vitamins A, D and E modulate immune responses. Beyond providing indispensable nutrients, diet can dynamically influence the immune system. Over 65% of the immune cells in the body are positioned in the gut, technically making the gut the "largest immune organ." The immune receptors of the innate immune system positioned in the gut are the primary targets of strategies for immunomodulation via diet. There are several areas that need to be addressed; the most important is to raise the awareness of the people for balanced uptake of nutrients.

A Review of Micronutrients and the Immune System–Working in Harmony to Reduce the Risk of Infection

“…Iron Involved in regulation of cytokine production and action [3]; required for generation of pathogen-killing ROS by neutrophils during oxidative burst [7] Copper Accumulates at sites of inflammation [7,35]; part of copper/zinc-superoxide dismutase, a key enzyme in defense against ROS [8]; free-radical scavenger [58]; changes in copper homeostasis a crucial component of respiratory burst [8]; important for IL-2 production and response [7,35]; maintains intracellular antioxidant balance, suggesting important role in inflammatory response [8] Selenium Essential for function of selenoproteins that act as redox regulators and cellular antioxidants, potentially counteracting ROS produced during oxidative stress [2] Magnesium Can help to protect DNA against oxidative damage [37]; high concentrations reduce superoxide anion production [59] Differentiation, proliferation and normal functioning of T cells Vitamin A Involved in development and differentiation of Th1 and Th2 cells [60]; enhances TGF-β-dependent conversion of naïve T cells into regulatory T cells [8]; plays a role in acquisition of mucosal-homing properties by T and B cells [8] Vitamin D Homing of T cells to the skin [61]; calcitriol inhibits T-cell proliferation [7]; inhibitory effects mainly in adaptive immunity (e.g., Th1-cell activity) [7]; stimulatory effects in innate immunity [7]; inhibits the effector functions of T helper cells and cytotoxic T cells [27,62], but promotes the production of Tregs [27,62,63]; inhibitory effect on the differentiation and maturation of the antigen-presenting DCs, and helps program DCs for tolerance [27,[64][65][66] Vitamin C Roles in production, differentiation, and proliferation of T cells, particularly cytotoxic T cells [3,21] Vitamin E Enhances lymphocyte proliferation and T-cell-mediated functions [3]; optimizes and enhances Th1 response [3] Vitamin B6 Involved in lymphocyt...…”

“…Vitamin A Development and differentiation of Th 1 and Th2 cells [8]; maintains normal antibody-mediated Th2 response by suppressing IL-12, TNF-α, and IFN-γ production of Th1 cells [7] Vitamin D Calcitriol suppresses antibody production by B cells [7] Vitamin C Promotes proliferation of lymphocytes, resulting in increased generation of antibodies [21] Vitamin E Suppresses Th2 response [3] Vitamin B6 Required in endogenous synthesis and metabolism of amino acids, the building blocks of antibodies [7]; inhibits Th2 cytokine-mediated activity [8] Vitamin B12 Important for antibody production and metabolism, via folate mechanism [7, 8,35]; required for optimal clonal expansion [8] Folate Important for antibody production and metabolism [7,8,35] Zinc Involved in antibody production, particularly IgG [69,70] Selenium Helps to maintain antibody levels [35] Magnesium Cofactor in antibody synthesis, role in antibody-dependent cytolysis and IgM lymphocyte binding [38] Responses to antigen Vitamin A Normal functioning of B cells, necessary for generation of antibody responses to antigen [7]; required for B cell-mediated IgA antibody responses to bacterial polysaccharide antigens [8] Vitamin D Promotes antigen processing [8]; role in the down-regulation of MHC-II [35] Vitamin E Helps to form effective immune synapses between and Th cells [27]; increases proportion of antigen-experienced memory T cells [71] Folate Important for sufficient antibody response to antigens [35] Zinc Involved in antibody response [8]; important in maintaining immune tolerance (i.e., the ability to recognize "self" from "non-self") [27] Figure 2. Micronutrients have key roles at every stage of the immune response [2,[7][8][9].…”

“…In animal models, vitamin E intervention reverses these changes by inhibiting PGE(2) production by macrophages, thus indirectly protecting T-cell function [27,29]. Selenium is essential for the function of selenoproteins, which act as redox regulators and cellular antioxidants and are thus important for the function of leukocytes and NK cells [35]. It also helps (via glutathione peroxidase) to protect against oxidative stress by removing excess and potentially damaging free radicals [8].…”

“…The development and differentiation of Th1 and Th2 cells is dependent on vitamin A, which supports the Th2 anti-inflammatory response by suppressing IL-12, TNF-α, and IFNγ production of Th1 lymphocytes [3,8]. In contrast, vitamin E is known to suppress the Th2 response [3,35]. Vitamin E, as well as vitamin B6, folate, and zinc, maintain the Th1-mediated immune response, while vitamin D inhibits Th1-cell activity [8,94,95].…”

“…Vitamin D is an immunosuppressive hormone [62]; calcitriol inhibits the proliferation and differentiation of T and B cells [7,27], but production of calcitriol by DCs "programs" T-cell homing to the epidermis, which is essential for long-term immune surveillance and maintenance of the barrier integrity [61,96]. In contrast, vitamins C and B12 facilitate the production of T cells, particularly cytotoxic T cells [24,35]. Zinc is also essential for the development, differentiation, and activation of T lymphocytes [8,49], while iron, copper, and selenium are important in their differentiation and proliferation [2,7,35].…”