Traditionally, herbal medicine has played a significant role in managing immune health. Modern medicine has limited applications in supporting the immune system to help enhance a person’s immune response. Fortunately, herbal medicine can pick up the slack, so to speak, and through various mechanisms elicit an immune response.
Herbal medicine can affect the immune system in a variety of ways including antioxidant activity; cytokine production; modulation of the activation and inhibition of T cells; stimulation of antibodies; and antimicrobial actions.
Here, we explore a couple of ways herbal medicine can support the immune system through a variety of actions.
A natural compound derived from Curcuma longa (turmeric), curcumin has promising applications as an antioxidant, antiviral, antibacterial, antifungal, anti-inflammatory and hepatoprotective. There has been much interest in its action as an immunomodulatory agent due to its interaction with a variety of immune cells including macrophages, dendritic cells (DC), B cells and T cells.
Mounting evidence suggests curcumin can inhibit the inflammatory response in immune cells and interacts with a variety of cellular and molecular targets, including transcription factors, various inflammatory mediators, cytokines, chemokines, CRP, ESR, PG-E2, immune complexes, surface markers of cells, and cell adhesion molecules.[2,3]
The suppression of inflammatory cascades in immune cells leads to the inhibition of the activation, maturation, and cytokine production of macrophages and DCs, important to innate immunity. It also results in the inhibition of activation, proliferation, maturation, and cytokine production of T cell subsets such as helper cells TH1, TH2 and TH17.
A herb popularly and traditionally used for its immune supportive properties across a wide array of illnesses and symptoms, andrographis has been studied for its anti-inflammatory, immunostimulatory and antibacterial properties, to name a few. Often referred to as ‘Indian echinacea’ due to being likened to its western herbal medicine counterpart, this herb is most commonly used as an immunostimulant.
Although studies have been mostly limited to cell and animal varieties, research suggests that andrographis works as an immunostimulant via stimulation of antigen-specific and non-antigen specific immune responses, particularly via its active constituent andrographolide.. Ethanol extract of fresh andrographis plant and purified diterpenes-andrographolide and neoandrographolide has been found to stimulate antibodies in animal studies. Furthermore, a human study found that methanol extracted andrographis increased peripheral blood lymphocyte production. It was thought that the immunostimulatory effects were mainly focussed in the dichloromethane fraction – specifically the diterpenes-andrographolide, 14-deoxyandrographolide and 14-deoxy-11, 12-didehydroandrographolide isolated from the dichloromethane fraction.
A staple in any herbalist’s kit, echinacea is well known for its immunomodulatory activity. It has been researched for a multitude of actions – antiviral, antibacterial, antioxidant, lymphatic and anti-inflammatory, to name a few.[6,4]
The effect of echinacea on monocytes, macrophages, natural killer (NK) cells, DCs, and T cells has been studied extensively.[4,6-8] Another novel approach in the way echinacea exerts its immunomodulatory action is through its polysaccharide content, specifically fructans or inulin-type fructans (ITFs). These are already well known as prebiotics, eliciting a positive response on the immune system via the gastrointestinal tract. In other plant compounds, fructans have shown direct immunomodulatory and antiviral effects. Much of the antiviral properties were shown to work via the enhancement of nitric oxide (NO) –a viral replication inhibitor. This has been demonstrated in commonly used herbs and foods, including garlic, onion, burdock and chicory.[6,9,10]
Often put to use as an immunomodulatory herbal medicine, astragalus is well placed for a number of different immune-related concerns. Traditionally used for the past 2000 years in Chinese medicine for promoting vitality, energy and Qi strength, it has become a popular feature in restorative and immune tonics.
Although limited studies have revealed the efficacy of astragalus, a 2016 study into the ability of astragalus to enhance host defence revealed the therapeutic properties of polysaccharides – considered one of the active constituents of astragalus. The polysaccharide component has demonstrated immunopotentiating properties in animal studies, including immunomodulatory effects in the treatment and prevention of bacterial and viral infections. The antiviral properties of astragalus are believed to be due to the one of the active contiuents, polysaccharides, indirectly modulating proinflammatory cytokines, resulting in stimulation of leukocytes and platelets that make up part of the ‘first response’ of the immune system.
Whilst there is an array of herbal medicines to support the immune system – many with a range of differing actions – it’s important to also recognise the synergistic action of herbs and how a combination formula can often bring about the best response.
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- Kahkhaie KR, Mirhosseini A, Aliabadi A. et al. Curcumin: a modulator of inflammatory signaling pathways in the immune system. Inflammopharmacol 2019;27:885–900. [Abstract]
- Abdollahi E, Momtazi AA, Johnston TP, et al. Therapeutic effects of curcumin in inflammatory and immune‐mediated diseases: A nature‐made jack‐of‐all‐ trades?. J Cell Physiol 2018;233:830– 848. [Abstract]
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- Okhuarobo A, Folodun JE, Erharuyi O, et al. Harnessing the medicinal properties of Andrographis paniculata for diseases and beyond: a review of its phytochemistry and pharmacology. Asian Pac J Trop Dis 2014;4(3):213-222. [Full Text]
- Dobrange E, Peshev D, Loedolff B, et al. Fructans as immunomodulatory and antiviral agents: the case of echinacea. Biomolecules 2019;9(10):615. [Full Text]
- Goldrosen MH, Straus SE. Complementary and alternative medicine: assessing the evidence for immunological benefits. Nature Reviews. Immunology 2004;4(11):912-21. [Abstract]
- Bone K. A clinical guide to blending liquid herbs. St Louis: Churchill Livingstone, 2003.
- Koo HN, Hong SH, Seo HG, et al. Inulin stimulates NO synthesis via activation of PKC-alpha and protein tyrosine kinase, resulting in the activation of NF-kappa B by IFN-gamma-primed RAW 264.7 cells. J. Nut. Biochem 2003;14:598–605. [Abstract]
- Chandrashekar PM, Prashanth KVH, Venkatesh YP. Isolation, structural elucidation and immunomodulatory activity of fructans from aged garlic extract. Phytochemistry 2011;72:255–264. [Abstract]
- Denzler K, Moore J, Harrington H, et al. Characterization of the physiological response following in vivo administration of Astragalus membranaceus. Evidence-Based Complementary and Alternative Medicine 2016. [Full Text]