The herb astragalus (Astragalus membranaceus)called huang in traditional Chinese medicine (TCM) has been used in TCM for thousands of years. Historically it has been used for strengthening chi or qi life force so it was typically employed in conditions related to general weaknesses in the body such as fatigue anemia poor appetite cardiovascular disease and other conditions associated with insufficient qi. It has been especially instrumental for kidney health. In modern times astragalus is still used for bolstering the immune system in general often in combination with ginseng and echinacea. 

The various forms of astragalus are native to Northeast Asia and grow extensively in China Korea Tibet and Mongolia. The plant is a perennial and grows to about 18-36 inches tall. It is used in tincture form but the more common application is for the roots to be dried and powdered then taken as a capsule or a tea. The herb's beneficial pharmacological effects may be due to its phytochemical components which include a host of saponins polysaccharides and flavonoids. It also contains twenty trace minerals including chromium cobalt copper selenium and molybdenum plus relatively high concentrations of manganese zinc and rubidium. 

Astragalus extracts have been shown to have immune-modulating properties in vivo and in vitro in animals as well as in humans. Mouse studies have demonstrated the herb's stimulatory influence on immune response cytokines while leaving inflammatory cytokines unaffected. Specific fractions isolated from astragalus increased production of the immune-modulating signaling compounds IL-1I² IL-2 and IL-8 in human blood cells in vitro. Astragalus has been shown to influence the proliferation of mouse spleen cells which may also modulate the immune response. Studies support the triterpene saponins in this herb as being the principal active components that result in increased IL-2 activity with IL-2 being a cytokine produced by activated T cells stimulating for both acquired and innate immune responses such as the release of secondary cytokines IL-1 and IL-6. Exposure to astragalus in mice in vivo increased the influx of macrophages to the treated region and also had a beneficial mitogenic effect on lymphocytes even restoring a reduced mitogenic response in older mice to that of younger mice. If future research supports a similar effect in humans then astragalus could potentially help boost the flagging immune systems of the elderly or other immune-compromised individuals.

Other immune-stimulating effects of astragalus include antiviral activity against myocarditis caused by coxsackie-B virus in mice and humans (via increased natural killer cell activity); in vitro antibacterial activity against Shigella dysenteriae Streptococcus hemolyticus and Staphylococcus aureus; and chronic cervicitis associated with human papillomavirus type-16 Herpes simplex virus type-2 and cytomegalovirus. Astragalus is also effective in raising white blood cell counts in a dose-dependent manner in patients with leukopenia lending more weight to the herb's utility for general immune system support and strengthening the body's natural defenses just the way TCM practitioners have employed it for centuries.

Additionally modern research has identified a mechanism behind the specific application of astragalus for kidney and urinary tract health. Compared to untreated control cells cultured human bladder epithelial cells exposed to a pathogenic strain of E. coli showed significant increases in expression of TLR4 a protein involved in pathogen recognition and innate immune system activation.  Astragalus demonstrated antimicrobial activity in these bladder cells stimulated secretion of IL-6 and IL-8 and influenced expulsion of pathogenic E. coli. Human and mouse bladder cells showed significantly reduced colonization by E. coli with astragalus compared to controls.

Astragalus has been shown to be safe even at high doses. No toxicity or adverse effects have been noted at animal doses equivalent to a human dose of 0.57 g/kg for a body weight of 70 kg. The LD50 in mice has been estimated at more than 1 gm/kg.