![]() The world is full of living organisms too small to be seen with the naked eye. Called microorganisms or microbes, these tiny critters can be found on doorknobs, our skin, car keys, and almost everything around us. They’re in the soil in our backyard, on the food we eat, and in the air. Most are harmless and some are extremely beneficial. Only a few cause disease, but they account for many disorders and contribute to human suffering worldwide. These challenges that are part of our world come from outside the body, but others come from within. Abnormal cells can develop due to inherited factors, environmental pollutants and many other reasons- some of which are unknown to us. Although we still have much to learn about what causes cells to become abnormal, we do know that our bodies dispatch many of them before they can develop into things like cancer. With all the microbes, environmental toxins and other stuff hanging around, why aren’t we constantly ill? …. (crickets)..... For this we can thank our bodies luscious and glorious defense mechanism system, which detects and wards off many of these threats before they have a chance to do us real harm. These mechanisms include physical and chemical barriers that prevent many harmful substances from entering the body (such as skin and stomach acid), nonspecific mechanisms that help the body respond to all kinds of tissue damage and specific defense mechanisms that recognize and kill particular microorganisms and abnormal cells (such as specific immune responses). All these mechanisms work cooperatively and simultaneously to protect us. They involve a wide variety of cells, proteins, chemicals and organs. The lymphatic system (Ta- DA!) plays a crucial role and in this blog post we will look at its function. These mechanisms also involve the immune system, a complex group of cells, proteins, and structures of the lymphatic and circulatory systems. The lymphatic system is closely associated with the cardiovascular system. The lymphatic system performs three important functions:
The lymphatic system helps to maintain blood volume and interstitial fluid volume by returning excess fluid that has been filtered out of the capillaries back to the cardiovascular system. Let’s take a look at how these various systems protect us from disease and injury. The above picture shows the structure of the lymphatic system. The lymphatic system begins as a network of small, blind-ended lymphatic capillaries in the vicinity of the cells and blood capillaries. The fluid in the lymphatic capillaries is lymph, a milky body fluid that contains white blood cells, proteins, fats and the occasional bacterium. The lymph is formed when the interstitial fluid (the fluid which lies in the interstices of all body tissues) is collected through lymph capillaries. Lymphatic capillaries merge to form the lymphatic vessels. Located at intervals along the lymphatic vessels are small organs called lymph nodes. Lymph nodes remove microorganisms, cellular debris, and abnormal cells from the lymph before returning it to the cardiovascular system. There are hundreds of lymph nodes clustered in the areas of the digestive tract, neck, armpits and groin. The lymphatic vessels carry lymph into and out of each node. Valves within these vessels ensure that lymph flows only in one direction. As the fluid flows through a node, the macrophages destroy foreign cells by phagocytosis, and the lymphocytes activate other defense mechanisms. The cleansed lymph fluid flows out of the node and continues on its path to the veins. The immune system is typically divided into two categories - innate and adaptive- although these distinctions are not mutually exclusive. Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood and immune system cells that attack foreign cells in the body. The innate immune response is activated by chemical properties of the antigen. Adaptive immunity refers to antigen-specific immune response. The adaptive immune response is more complex than the innate. The antigen must first be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells that are specifically designed to attack that antigen. Adaptive immunity also includes a “memory” that makes future responses against a specific antigen more efficient. There are two types of adaptive immune responses: humoral immunity, mediated by antibodies produced by B lymphocytes, and cell-mediated immunity, mediated by T lymphocytes. Humoral and cell-mediated immunity are together responsible for coping with foreign bodies like viruses and bacteria that enter a human organism and cause various diseases. In the adaptive immune system, humoral immunity is responsible for viruses and bacteria that have not yet penetrated into the cell. The cells that make humoral immunity possible are known as b-cells, which contain b-lymphocytes. In the adaptive immune system, cell-mediated immunity is responsible for viruses and bacteria that have penetrated into the cell. The cells that make cell-mediated immunity possible are known as t-cells, which mature in the thymus. Overall, humoral immunity is an aspect of immunity that is mediated by macromolecules found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides. Humoral immunity is so named because it involves substances found in the humors or body fluids. The humoral immune response begins with the recognition of antigens by naive B cells. These cells then undergo a process of clonal expansion and differentiation. Through this process, the B cell matures into antibody secreting plasma cells, which secrete antibodies. Antibodies are proteins that bind with and neutralize specific antigens (any substance that mobilizes the immune system and provokes an immune response). B cells release antibodies into the lymph, bloodstream, and tissue fluid, where they circulate throughout the body. Antibody-mediated immunity works best against viruses, bacteria, and foreign molecules that are soluble in blood and lymph. The T-cells responsible for cell-mediated immunity develop from stem cells in bone marrow but mature in the thymus gland. T-cells directly attack foreign cells that carry antigens, or release substances that enhance the immune response. When a T-cell with CD4 receptors encounters an APC displaying an antigen-MHC complex, it differentiates into a helper T-cell. Helper T-cell do not directly kill infected cells, as cytotoxic T-cells do. Instead they help activate cytotoxic T-cells and macrophages to attack infected cells or they stimulate B-cells to secrete antibodies. The role of the helper T-cell is crucial. Without them the entire immune response would be severely impaired or nonexistent because they direct or enhance the activities of so many other cells in the immune system. The regulatory T-cells (formerly known as suppressor T-cells in one of the texts book I’m perusing) are a subpopulation of T-cells which modulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune disease. Finally, cytotoxic T-cells kill abnormal and foreign cells. When a mature T-cell with a CD8 receptors meets an APC that displays an antigen-MHC complex, it is activated to produce a clone of cytotoxic T-cells, also called (MY FAVORITE) killer T-cells or T8s. These are the only T-cells that directly attack and destroy other cells. Once activated, these killers roam through the body. They circulate through blood, lymph, and lymphatic tissues in search of cells that display the antigens they recognize. They migrate to a tumor or site of infection, where they release chemicals that are toxic to abnormal cells. Ugh- so sweet Herbal medicine can help in tending to your inner army...
From strengthening and modulating the immune system with medicinal mushrooms and plants like astragalus, codonopsis, and elder to treating common infections with echinacea and the garden-variety antimicrobials such as oregano, thyme and bee balm, there is SO MUCH in the realm of plant medicine to assist humans in tending our inner army.
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AuthorThe adventures, studies, and musings of a student at the Vermont Center for Integrative Herbalism.
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