Table 1.
Summary of the effects of various micronutrients on different aspects of immunity.
| Micronutrient | Role in barrier function | Role in cellular aspects of innate immunity | Role in T-cell mediated immunity | Role in B-cell mediated immunity |
|---|---|---|---|---|
| Vitamin A | Promotes differentiation of epithelial tissue; promotes gut homing of B- and T cells; promotes intestinal immunoglobulin A+ cells; promotes epithelial integrity | Regulates number and function of NK cells; supports phagocytic and oxidative burst activity of macrophages | Regulates development and differentiation of Th1 and Th2 cells; promotes conversion of naive T cells to regulatory T cells; regulates IL-2, IFN-γ and TNF production | Supports function of B cells; required for immunoglobulin A production |
| Vitamin B6 | Promotes gut homing of T cells | Supports NK-cell activity | Promotes T-cell differentiation, proliferation and function, especially Th1 cells; regulates (promotes) IL-2 production | Supports antibody production |
| Vitamin B9 (Folate) | Survival factor for regulatory T cells in the small intestine | Supports NK-cell activity | Promotes proliferation of T cells and the Th1-cell response | Supports antibody production |
| Vitamin B12 | Important co-factor for gut microbiota | Supports NK-cell activity | Promotes T-cell differentiation, proliferation and function, especially cytotoxic T cells; controls ratio of T-helper to cytotoxic T cells | Required for antibody production |
| Vitamin C | Promotes collagen synthesis; promotes keratinocyte differentiation; protects against oxidative damage; promotes wound healing; promotes complement | Supports function of neutrophils, monocytes and macrophages including phagocytosis; supports NK-cell activity | Promotes production, differentiation and proliferation of T cells especially cytotoxic T cells; regulates IFN-γ production | Promotes antibody production |
| Vitamin D | Promotes production of antimicrobial proteins (cathelicidin, β-defensin); promotes gut tight junctions (via E-cadherin, connexion 43); promotes homing of T cells to the skin | Promotes differentiation of monocytes to macrophages; promotes macrophage phagocytosis and oxidative burst | Promotes antigen processing but can inhibit antigen presentation; can inhibit T-cell proliferation, Th1-cell function and cytotoxic T-cell function; Promotes the development of regulatory T cells; inhibits differentiation and maturation of dendritic cells; regulates IFN-γ production | Can decrease antibody production |
| Vitamin E | Protects against oxidative damage | Supports NK-cell activity | Promotes interaction between dendritic cells and T cells; promotes T-cell proliferation and function, especially Th1 cells; regulates (promotes) IL-2 production | Supports antibody production |
| Zinc | Maintains integrity of the skin and mucosal membranes; promotes complement activity | Supports monocyte and macrophage phagocytosis; supports NK-cell activity | Promotes Th1-cell response; Promotes proliferation of cytotoxic T cells; promotes development of regulatory T cells; regulates (promotes) IL-2 and IFN-γ production; reduces development of Th9 and Th17 cells | Supports antibody production particularly immunoglobulin G |
| Copper | Promotes neutrophil, monocyte and macrophage phagocytosis; supports NK-cell activity | Regulates differentiation and proliferation of T cells; regulates (promotes) IL-2 production | ||
| Iron | Essential for growth and differentiation of epithelial tissue | Promotes bacterial killing by neutrophils; regulates balance of M1 and M2 macrophages; supports NK-cell activity | Regulates differentiation and proliferation of T cells; regulates IFN-γ production | |
| Selenium | Supports NK-cell activity | Regulates differentiation and proliferation of T cells; regulates (promotes) IFN-γ production | Supports antibody production |
IFN Interferon, IL interleukin, NK natural killer, Th T-helper, TNF tumour necrosis factor.