LITMIR.BIZ

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in making what is often a very difficult diagnosis to establish. That is why this book must start with a treatise on the immune system

      An understanding about the mechanism involved in the etiology of a puzzling illness, and often a chronic one at that, is crucial for any patient to be able to understand, accept and learn to live within its context. And I stress again: in the treatment of these unusual diseases, there is nothing more important than an educated patient working in collaboration with a dedicated physician. It can be a partnership guaranteeing the best possible result.

      IMMUNE SYSTEM

      With that in mind, we will first discuss the immune system, the story of the body’s defenses; how the body confronts enemies trying to do us harm. This short story will provide a better understanding of the amazing way this life and death struggle takes place. It is a coordinated system combining the beauty of organs, cells, and complicated collections of proteins working in a harmonious manner for the good of the whole. There are various lines of defense used to keep us alive in a world where invisible or visible predators attack us minute by minute. Besides the foreign substances that can invade us as mentioned above (bacteria viruses, fungi and parasites), we must also include pollen, cancer cells, and internal body cell changes arising spontaneously; the pollen invading us from the outside, the cancer cells invading us from within, the internal body changes arising spontaneously—now all considered foreign and subject to an all-out assault by the immune system.

      Getting right down to the details of the immune response, let me advise that the principle mechanism of our specific immune response is carried out by two members of the white blood cell team known as T lymphocytes and B lymphocytes. These two types of white blood cells circulate in our blood stream and position themselves in body tissues by the billions. Their job is to:

      •Identify body cells (self) that have changed, thus the lymphocytes do not identify them as belonging to the body, but rather view them as non-self—and attack.

      •Identify invaders of the body that certainly do not belong (non-self)—and attack.

      In other words, lymphocytes differentiate self from non-self—and anything non-self is eliminated (killed). How do they do this?

      All body cells carry distinctive molecules (epitopes) on their surfaces that identify it as self. Our specific immune cells, (lymphocytes), recognizing this self-marker, coexist in a peaceful state known as self-tolerance. Failure to recognize this body self-marker as self, launches a vigorous attack by lymphocytes. What are these immune cells (B cells, T cells)?

      Before we get into this very specific line of defense where B cells and T cells attack specific invaders, understand that there is also a mechanism constituting a first line of defense categorized as nonspecific body defenses because they are not programmed to zero in on specific targets like our lymphocytes do, but rather “kill ‘em all.”

      As this non-specific line of defense is different from the B and T cells, I have placed them in an appendix so as not to disrupt the story of the specific line of defense. The reader has the choice to read it now or save it for after completing the book. (SEE APPENDIX 1

      The red bone marrow is where all blood cells are manufactured including the B cells or B lymphocytes, and T cells or T lymphocytes constituting the specific line of defense. The thymus gland is responsible for putting the final touches on the T cells, producing functioning T cells, or T lymphocytes. Again, these B and T cells are the lymphocytes that are responsible for the specific immune responses.

      The red bone marrow where B cells and T cells are produced is also the site of production for all the other cellular elements of the blood including:

      1.Red blood cells

      2.All the other various types of white blood cells (4) besides the B&T lymphocytes.

      3.Blood platelets—important in blood coagulation.

      Red bone marrow in adults is located in flat bones (sternum) and in the epiphysis (the end of long bones).

      Within the red bone marrow is a stem cell known as a hemocytoblast. Hemo, from the Greek haima (blood), cyto (cells), blast, from the Greek blastos, sprout. This precursor stem cell evolves (sprouts) into two other cells:

      •lymphoid stem cell that forms B & T lymphocytes.

      •myeloid stem cell that forms the red blood cell, the platelets, and four different white blood cells, the basophil, the eosinophil, the neutrophil, and the monocyte.

      These white cells arising from the myeloid stem cell precursors are called leucocytes or white blood cells (from the Greek, leuco white). The latter four are involved in the non-specific system of defense. Again, SEE APPENDIX ONE.

      1.The basophil is the rarest of the white blood cells. Filled with histamine granules, it dilates blood vessels and makes them more permeable. In addition, it is one of the agents responsible for attracting other white blood cells to action.

      2.The eosinophils increase in number and rally to the cause during infection by parasites, and in response to allergens (any substance that can cause an allergy).

      3.The neutrophils are actively involved in phagocytosis (ingesting and digesting bacteria). They have a ravenous appetite for invading bacteria.

      4.The monocytes are the largest of all the white blood cells and they change into macrophages when they migrate into tissues from the blood stream. Macrophages have an appetite for bacteria that can cause long standing chronic infections such as tuberculosis.

      SPECIFIC IMMUNITY

      Let us define immunity again: the body’s ability to defend against specific invaders (viruses, bacteria, toxins, parasites).

      This is a very complex subject, the details of which could probably occupy ten volumes. I am going to discuss it, if for no other reason than to acquaint you with the complexity that has evolved in the last sixty years from very little knowledge of the subject of immunity to the great detail and understanding of today.

      An antigen is a foreign substance that invokes an immune response. The ability of the body to recognize a foreign molecule (antigen) also means that the body can recognize self from non-self and can memorize. This means that the next time the foreign invader returns, the body will be able to launch an immediate and vigorous response because they have prepared themselves in greater volume of numbers to be ready for another onslaught by the same invader.

      Remember that the lymphocyte B cells and T cells both develop from the stem cells in the red bone marrow:

      •T cells form in the bone marrow (pre-T cells), and they migrate to the thymus where they complete their development and become immunocompetent T cells. Immunocompetent means they have the ability to carry out immune responses.

      •B cells complete their development in the bone marrow.

      Both B and T cells then circulate in the blood stream, but not before they have acquired surface proteins (antigen receptors), molecules that are capable of recognizing specific antigens.

      The red bone marrow and thymus gland are primary lymphatic organs because they produce B and T cells. The thymus gland lies behind the sternum and extends upward to the base of the neck. At birth, it weighs about half an ounce (10-15 grams). It grows until puberty when it reaches about 1½ ounces (30-40 grams). After this, it begins to atrophy so that by age forty it is back to birth size and by age seventy it is less than ten grams. Most of the body’s T cells develop before puberty. Some develop throughout life, but to a lessened degree. As we advance in years, the effectiveness of our T cell response decreases making us more susceptible to disease.

      The thymus liberates a hormone known as thymosin, which stimulates the growth of the thymus and the development of the lymphocytes. Once the lymphocytes have matured, they take up station in one of three places: some remain in the thymus and are the source of future T cell lymphocyte needs; some enter the blood circulation; and some lodge in other lymphoid tissue.

      OTHER

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