In Part I of this series we reviewed the inflammatory response system, and now turn to the immune system, which is dynamic and has a lot of moving parts, and because it is complex, it may be easier to grasp when its various parts are presented separately.
In Parts II and III we’re going to talk about the mechanics of our body’s defense system. Part IV will wrap up the physiology with a review of the immune system’s close relative, the lymph system.
The point of this series is to lay the groundwork for later topics as diverse as auto-immune and other disorders, nutrition, and health tips, and provide basic terminology if and when you are presented with information about common health topics such as infections and inflammation.
To begin, there are types of immunity: non-specific and specific, and there are different kinds of defensive cells: primarily white blood cells, immunoglobulins, and microphages and macrophages. Immunity is a way to protect against microbial and non-microbial invaders; while we refer frequently to living organisms, trauma from injury or as a result of disease are other primary factors that can rally the immune system into action.
Specific and Non-Specific
In a nutshell, non-specific (innate) immunity is the first line of defense against microbes and can tell the difference between “self” and not-self,” but cannot differentiate further. Specific (acquired/adaptive) defense can differentiateand respond to each foreigner uniquely.
Some of the players work in both innate and acquired immunity, some do not.
Part II: Innate Immunity: Where and How
1) THE SKIN AND MUCOUS MEMBRANES: mechanical and chemical defenses1) Anatomical: the skin and mucous membranes that line the gastrointestinal , reporductive, and respiratory tracts are the mechanical first-line-of-defense.
The tissue of the skin and mucous membranes are made up of densely packed cells and short of injury, prevent penetration of unwanted invaders.
Other mechanical barriers to microbes are tears, saliva, the hairs that line your nose, and the flow of urine.
In conjunctions with mechanical forces, chemical defenses prevent colonization of microbes by a shift in the acid-alkaline balance or through enzymatic action. For example, increased acidity in the stomach and on the skin, the presence of fatty acids in the oil glands of the skin, and the enzyme lysozyme in tears, saliva, and other body fluids.
2) ANTI-MICROBIAL SUBSTANCES: Complement, Factor P, and Interferon
Complement is a group of proteins present in blood serum. It is so named because it complements the immune system by enhancing its ability to recognize, attach and destroy invading microbes. Complement is activated in both non-specific and specific immunity.
Properdin, or Factor P, is another protein in blood serum that works with complement. Properdin triggers the inflammatory responses, enhances phagocytosis (see below), and neutralizes bacterial or viral invaders.
Interferons are proteins that communicate between cells, signaling a call-to-action and tracking locator for other immune cells to come find and fight.
In a nutshell, the body produces cells that envelop and destroy foreign, invading substances, via a two-part mechanism, adherence and ingestion: the cell membrane of the phagocyte attaches to the microbe, traps it, engulfs it, and destroys it. Microphages and macrophages are the key immune cells of the phagocytic system, found all over the body, in the blood, bone marrow, tissue, lymph nodes, and organs (liver, lungs, brain, and spleen).
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