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By Marcia Zimmerman

Understanding the science behind five important immune-stimulating herbs and the complex immune system can help you learn how to stay healthy and prevent disease. From ligustrum to licorice, botanical medicines are nature's healers.

One way of keeping your immune system healthy is to support it with herbal remedies, used for hundreds, sometimes thousands of years. Herbal medicines have a long, successful track record for human use, and now scientific research confirms many of the folk medicine traditions. Access to these herbs is as simple as buying them at your natural products store, although you should have a health professional check your condition before starting any herbal regimen.

    Your immune system is the interdependent group of bodily organs and substances that protects the body from invasion by foreign organisms. It comprises mainly the spleen, thymus, lymph nodes, lymphocytes including B- and T-cells, antibodies, and lymphoid tissue such as the gastrointestinal tract and bone marrow.

    Five botanicals—echinacea, astragalus, ligustrum, shiitake mushrooms and licorice—have proven beneficial in assisting the immune system in its task of keeping us healthy. In order to clarify the terms used to describe the action of these botanicals, it's helpful to discuss how white blood cells work within the immune system.

    White blood cells are considered the soldiers of the immune system. They're manufactured in the bone marrow, and mature cells "wiggle" out of blood vessels into spaces within cells throughout the body that are filled with tissue fluid. Here they move freely to protect the tissue. White blood cells include five types—lymphocytes, monocytes, basophils, neutrophils and eosinophils— each of which can be broken down into many forms, giving the immune defense force an array of physical and chemical weapons.

    Some lymphocytes migrate into lymphatic tissue including the thymus and lymph nodes. Here they're transformed into T-cells and B-cells that provide immunity to these organs. T-cells produce hormonelike proteins called cytokines including interferon and tumor necrosis (killing) factor. B-cells turn into plasma cells that produce antibodies such as immunoglobulins that attack harmful antigens, substances such as bacteria that stimulate the immune response. Antibodies "remember" the antigen and hamper further efforts to enter the body. This gives the body future protection against the antigen and is called humoral immunity. Further differentiation of lymphocytes produces natural killer cells that specialize in destruction of foreign cells such as cancer.

    Monocytes swell into larger cells called macrophages once they enter the tissue fluid. Some macrophages attach themselves to tissue, while others roam about. These large, active cells are the first to react when encountering infection or trauma. They send a chemical message to other white blood cells alerting them to advance and attack the invader.

    Basophils migrate into intercellular spaces and form mast cells. These proliferate in the presence of allergens (allergy-producing substances) and release a protein called histamine. Histamine's role is to protect the body; however, if the immune system becomes oversen-sitized to histamine, it can identify it as an enemy and initiate an allergic response.

    Neutrophils, the white blood cells alerted to danger by the macrophages, rove about in search of bacteria and viruses that have entered the body. Once neutrophils have identified the invaders, they destroy them. Eosinophils respond when chemical contaminants enter the body. Their job is to contribute to the inflammation that will remove the toxic threat.

    Now that we've identified the immune system, here's how the five botanicals fit into the picture. This information is not meant to be used as medical advice.

Echinacea

Echinacea is a native American herb that has two species: Echinacea purpurea is the species that grows in the eastern states, and Echinacea angustifolia covers the prairie states.

    Echinacea possesses a wide range of chemical constituents; among them are polysaccharides, phenols and the alkylamine echinacein. The polysaccharides (complex carbohydrates) in echinacea have been shown to bind with hyaluronic acid, a protective agent in cellular membranes and intercellular fluids. By binding with this acid, echinacea polysaccharides resist the action of an enzyme secreted by bacteria and viruses that destroys hyaluronic acid. This enzyme makes holes in cellular membranes to facilitate the entry of bacteria and viruses, with the subsequent destruction of the cell. Hyaluronic acid is also an important component of fibroblasts that heal tissue. By helping to maintain hyaluronic acid, echinacea promotes healing, as has been shown with topical application.

    Echinacea polysaccharides also have anti-inflammatory ability to reduce swelling and repair injured tissue. Additionally, these polysaccharides have shown both macrophage-stimulating activity and vigorous activation of white blood cells in destroying bacteria, viruses and toxins.

    The phenols in echinacea (chlorogenic and chicoric acids) are designated echinacosides (the healing constituents in echinacea). These show antibiotic- and immune-stimulating activity.

    Another active ingredient, echinacein, is responsible for the familiar tongue "tingle" of high-quality, fresh echinacea root or its extract. Echinacein inhibits growth of bacteria and fungus and stimulates the system that helps kill bacteria and viruses.

    Echinacea is a powerful immune activator, and it's generally used for a course of treatment and then discontinued. Its healing power is enhanced by use in combination with other immune-activating botanicals.

Astragalus

Astragalus membranaceous is one of the most important tonic herbs in the world. Its use can be traced back at least 2,000 years in China. In Chinese medicine, astragalus is considered a chi super tonic, which means it increases our ability to function fully and adapt to our surroundings. As such, astragalus is generally believed to modulate the activity of the immune system. These effects have been studied by modern researchers and are attributed to two classes of chemical compounds found in astragalus—polysaccharides and saponins.

    Astragalosides (the healing constituents of astragalus) have multiple effects on the bone marrow, spleen and humoral immunity. In bone marrow, astragalosides have demonstrated increased activity of the white blood cells. This is one reason why astragalus has been used with immunosuppressing agents such as chemotherapy and radiation. Chinese medical doctors use a number of herbs including astragalus and ligustrum to increase defense function in patients receiving chemotherapeutic drugs.

    Astragalosides increase the number and activity of phagocytes (cells that digest substances such as bacteria) in blood and tissue fluid and enhance the transformation of lymphocytes into T-cells. As we've seen, these effects begin in the bone marrow, then continue throughout the body. The astragalosides increase the release of antibodies and improve adherence of enzymes to the surface of macrophage cells so they become more sensitive and aggressive. Astragalosides are effective in increasing cytokine activity, which inhibits viral activity.

    The primary action of the saponin astramembrannin is antioxidant protection. This agent protects the liver from the damaging effects of toxins.

Ligustrum

Ligustrum lucidum, considered a major tonic herb in Chinese medicine, is often used in conjunction with astragalus in immune-restorative therapy. In this combination, these two herbs have been found to increase the bone marrow production of lymphocytes as well as their conversion to T-cells. Ligustrum and astragalus together can also raise immunoglobulins, lending strength to disease resistance.

    Tumor growth inhibition has also been attributed to ligustrum. The active constituents found in ligustrum are fatty acids including oleic acid, linoleic acid, oleanolic acid and ursolic acid, and sugars including glucose, fructose and alpha mannitol.

Shiitake Mushrooms

Shiitake mushrooms, Lentinus edodes, contain polysaccharides called lentinan that stimulate macrophages and natural killer cells to act more quickly and aggressively. Lentinan stimulates the thymus gland to convert lymphocytes into T-cells including T-helper cells. This in turn increases the effectiveness of macrophages. Lentinan also activates the enzymes in the blood that neutralize toxins, increases the chemical messages between white blood cells, stimulates phagocytosis (ingestion of bacteria) and splits bacterial membranes so they can easily be destroyed.

Licorice

Licorice, Glycyrrhiza glabra, complements the action of almost any herb. It helps direct the chief herbal actions and reduce side effects. Glycyrrhiza and its various species contain many active components including glycyrrhizin, glycyrrhetinic acid, phenols and saponins. Glycyrrhizin has shown ability to inhibit viral replication. Glycyrrhetinic acid and glycyrretic acid have demonstrated ability to slow viral growth and reduce inflammation. Several phenolic compounds in licorice have shown other viral-inhibiting activities as well as ability to reduce oxidative damage from xanthine oxidase enzyme.

    Licorice saponins increase the number of antibodies produced by plasma cells. They also activate the production of interferon by lymphocytes and reduce tumor growth by slowing cellular reproduction. Saponins are also responsible for the antiulcer activity of licorice.

Marcia Zimmerman, M.Ed, C.N., is a writer and lecturer on the biochemical role of supplements. For more information on herbal remedies, visit Delicious! Magazine at http://www.newhope.com on New Hope Group's World Wide Web home page.

Reprinted with permission from the October 1995 issue of Delicious! Magazine, a publication of New Hope Communications, Boulder, CO.