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The Immune System / The Thymus Gland
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Serveral authors have made interesting comments regarding the thymus:
"THYMUS GLAND…Lying beneath the sternum (breastbone) and above the treachea (windpipe) and heart is the two-lobed thymus gland; each lobe is made up of LYMPHATIC tissue. The thymus gland plays a significant part in the establishment of the immune system from the 12th week of gestation until PUBERTY, after which it begins to shrink gradually." (Stoppard, M.D., page 84)
"thymus...a ductless, glandlike body, of undetermined function, situated in the upper thorax near the throat: it is most prominent at puberty, after which it disappears or becomes vestigial: the thymus of an animal, when used as food, is called sweetbread..." (Webster's Dictionary, page 1,906)
"There is still considerable ignorance about exactly how the thymus does its job, but it is now known that it is essential for the proper running of the lymphatic system, and that it has really carried out its major function during the first few years of life." (Weston, M.D., pages 98-99)
"Thymus gland. An imperfectly understood gland, the thymus is believed to produce thymosin, which promotes the development of antibodies, especially T lymphocytes, or T cells. The thymus stops working after puberty." (Time-Life, page 75)
"The thymus is found in the upper part of the chest, where it lies just behind the breastbone. In a young adult it is a few centimeters long and weighs about 15 gm. (one-half ounce). However, this simple statement conceals the most remarkable thing about the thymus, and that is the way that, quite unlike any other organ, it is at its largest at about the time of puberty when it may weigh up to 45 gm (one and one-half ounces). In a baby, the thymus is really very large compared to the rest of the body, and it may extend quite a long way down the chest behind the breastbone. It grows quite quickly until about the age of seven; after this the thymus continues to grow, but much more slowly until puberty. After the age of puberty the thymus starts to shrink in size--a process called involution--until in an elderly person there may be no more thymus tissue present apart from a bit of fat and connective tissue." (Weston, M.D., pages 98-99)
"Hormones secreted by the bilobed thymus stimulate the production of white blood cells" (Thomas, M.D., page 239)
"There seems to be little doubt that in the early years of life the thymus is concerned with programming the way in which the body resists infection, and in particular, it seems that the thymus is responsible for making sure that the system does not turn its activities against the body's own tissues." (Weston, M.D., page 99)
"The thymus, a member of the lymphatic system, is located in the anterior/superior mediastinum (just above and in front of the heart). It is known to play a critical role in the seeding of the lymphatic organs (lymph nodes, diffuse lymphatic tissue, etc.) with potential "T" lymphocytes, which secrete a substance that attacks the protein of certain tumor cells, foreign cells, and micro-organisms (cellular immunity). There is evidence that the thymus produces a hormone (thymosin) that enhances the development of "T" lymphocytes. Activity of the thymus wanes significantly after puberty; it ultimately atrophies to be replaced with fibrous tissue." (Kapit and Elson, Anatomist, page or plate 106)
"Thymus hormones travel through the bloodstream and continue to exert their influence over the departed T cells. Thus, the thymus can be considered to be a true endocrine gland-- carried to another part of the body where it will have its effect. We know that the thymus continues to secrete hormones and to 'train' and export T cells until late in life. After puberty it diminishes in size because it is no longer concerned with growth. Any further shrinkage is due to stress and other factors to be discussed in this book." (Diamond, M.D., page 10)
"In embryonic and early life the thymus gland is vitally concerned with growth, as has been demonstrated by the fact that administration of thymus extract dramatically increases growth rate in laboratory animals. More importantly, it is the 'school and factory' for lymphocytes--the white blood cells responsible Under the influence of thymus hormones, these cells mature, then leave the thymus and settle in the lymph nodes and the spleen, where they give rise to other generations of lymphocytes called T cells (T for thymus-derived). Thymus hormones travel through departed T cells. Thus, the thymus can be considered to be a true endocrine gland--that is, an organ that secretes a hormone into the bloodstream to be carried to another part of the body where it will have its effect." (Diamond, M.D., page 10)
"In the fetus and newborn animal, the thymus gland is a large organ lying in the upper mediastinum beneath the sternum. In the very young fetus it is composed primarily of epithelioid cells, but it has a reticular structure that entraps stem cells circulating in the blood. For reasons not understood, these trapped stem cells are then stimulated to proliferate extremely rapidly, and the cells that are formed are the first lymphocytes to appear in the fetus. These lymphocytes migrate into the blood and thence throughout the body, seeding the lymph nodes and other lymphoid tissue. The seeded cells then become either plasmablasts, the progenitors of the plasma cells, or lymphoblasts, the progenitors of the small lymphocytes formed in the lymphoid tissue. Thus, the thymus plays an important role in the original genesis of the entire lymphoid system of the body." (Guyton, M.D., page 122)
"Failure of the Immune System to Develop in the Absence of the Thymus Gland. If the thymus gland is removed early in fetal life, the lymphoid tissue of the entire body fails to become seeded with lymphocytes, and consequently, essentially no immune system develops. Even if the thymus is removed shortly before birth of the baby or within the first few days after birth, the immune system is still greatly impaired. Furthermore, the lymphocytic type of immunity seems to be much more impaired than the humoral type, indicating that plasmablast seeding of the lymphoid tissue occurs earlier than lymphoblast seeding. However, if the thymus gland is removed from an animal a few weeks to a few months after birth, very little harm is done to the immune system, because by that time enough seeding of the lymphoid tissue has occurred for the immune system to function throughout life. One exception to this occurs as follows: If the person is subsequently exposed to some effect, such as a nuclear bomb blast, that destroys most of his immune system, he will have difficulty reseeding his lymphoid tissue without the availability of a thymus gland. Here again, lymphocytic immunity is affected much more severely than is humoral immunity." (Guyton, M.D., page 122)
"Possibility of a Thymic Hormone. Even though the thymus gland is absolutely necessary for the early seeding of lymphoid tissue with lymphoblasts and plasmablasts, once this seeding process has occurred, one might expect that the lymphoblasts and plasmablasts could proliferate within the lymphoid tissue without further intervention from the thymus gland. Yet, even so, removal of the thymus gland still stops or greatly impedes further growth of the lymphoid tissue. If the thymus gland is then re-implanted can get out of the thymus gland, the lymphoid tissue throughout the body immediately resumes its growth. Therefore, it is believed that some hormonal substance released by the thymus gland diffuses throughout the body to activate the growth of the lymphoid tissue. This substance is called simply the thymic hormone. Thus far all attempts to extract from the thymus gland a specific substance that will perform all the functions of the so-called thymic hormone have failed. Nevertheless, there is still reason to believe that such a hormone might exist and that eventually it will be extracted." (Guyton, M.D., page 122)
A person with an underactive thymus gland will be prone to getting sick often. Infection will be common and will often be chronic and
prolonged. Allergies will also be more likely. Other symptoms include swollen glands, depression, extreme sweating, puffiness of the throat. The person will be a likely candidate for cancer.
"Immunodeficiency diseases are well recognized in the human. These diseases range from the selective deficiency of where both the T and B cell systems are lacking. Treatment depends on the determination of the specific immunodeficiency and some positive results have been demonstrated by transplantation of bone marrow and thymus and by the use of the hormone thymosin. Presently we know more about the specific deficiency diseases than we do about effective treatments." (Chaffee, pages 308-309)
"Diet can affect immune system function. Malnutrition, a deficiency of protein or the trace element zinc, or dietary excess may all have a profound effect on the development of disease. A severe deficiency of protein at an early age can slow or stunt growth of the thymus, impairing the normal functioning of T-cells." (Thomas, M.D., page 217)
"Perhaps most provocative and least understood is thecomplex connection between the immune system and the brain. Mental stress, both moderate and severe, can affect the workings of our white blood cells. In one study, it was found that patients hospitalized for severe depression had suppressed or underactive immune systems, making them more vulnerable to infections and disease. Another study showed that the suffering of a widower over the loss of his wife may harm his health: Bereavement seems to prevent lymphocytes from reacting appropriately. Even the much milder strain of taking an exam appears to reduce T-cell activity." (Thomas, M.D., pages 217 and 219)
"Nerve cells and immune cells seem to engage in two-way conversations. Some immune cells have receptors on their membranes for neuropeptides, chemicals produced by the brain. One group of neuropeptides, known as endorphins, may at response to mental stress seem to suppress the activity of T-cells, perhaps robbing us of help in fighting cancer cells. In some cases, the endorphins appear to have the reverse effect: When we are injured, they may boost our immune response by helping to attract
"Until the 1950s little was understood about the thymus, although there had been clues to its function for many years. As far back as 1902, Foulerton, a London physician, was using thymus extract in the treatment of cancer. However, the standard teaching was that the thymus gland had no function at all in the adult, a delusion fostered by the fact that during autopsy the thymus was usually found to be quite small and atrophied." (Diamond, M.D., page 8)
"Probably the most acceptable theory of cancer is that formulated by Sir MacFarlane Burnet, (F.M.Burnet, Immunology, Aging, and Cancer...San Francisco: W.H. Freeman and Company, 1976), the Australian Nobel Prize winner. Of the billions of new cells produced in the body each day, some will be abnormal. One of the functions of the T cells is to recognize these abnormal cells and destroy them. However, if the T cells are not activated by the thymus hormone, the abnormal cells may 'take' and develop into clinical cancer. Hence the critical role of the thymus gland throughout adult life in the prevention of cancer." (Diamond, M.D., page 11)
"Now we begin to understand why cancer increases with age It has been shown that the antibody response of old mice is only about 5 percent that of young mice. Old mice cannot reject cancer cells injected into them. However, if old mice are given thymus hormone at the same time, cancer does not develop. In all mammalian species there is a falling off in thymus activity with advancing years, and a corresponding increase in the rate of cancer. The more we can stimulate thymus activity throughout life, the greater will be our ability to ward off cancer." (Diamond, M.D., pages 11-13)
"The thymus gland, then, prepares the T cell to do its work--to distinguish self from not self, friend from foe, and to destroy foreign cells. This role, called immunological surveillance, is directly concerned with resistance to infections and cancer." (Diamond, M.D., page 10)
"Above, a T cell,, a thymus-derived lymphocyte, attacks a cancer cell...large sphere...which it identifies by the antigen molecules protruding from its surface. Below, the cancer These micrographs were made by Andrejs Liepins of the Sloan-Kettering Institute for Cancer Research." (Diamond, M.D., page 13, Figures 1 and 2)
"In a human being or an animal in which the thymus gland has been removed or destroyed, there is a loss in effectiveness of the immune mechanisms of the body that guard against infection and cancerous growth. For example, if a young rat that has had its thymus removed is injected with cancer cells, the cancer will take over and the rat will die. However, if the thymus gland is intact, the tumor will be recognized as a hostile invader and will be rejected. There is now considerable evidence that enhancement of the immune response by administering thymus extract can overcome some forms of clinical cancer. A search of the literature shows, as I stated above, that thymus extract was used clinically for the treatment of cancer as long ago as 1902." (Diamond, M.D., pages 9-10)
"B-cells make up one class of lymphocytes. The second class, known as T-cells, mature in the thymus (T stands for thymus). One subgroup of these T-cells, known as killer T-cells, attack and destroy certain cancer cells...cells infected by viral agents, and the cells of transplanted tissue." (Thomas, M.D., pages 186 and 196)
"T cells also attack cancer cells, slowing tumor growth." (Clayman, M.D., page 127)
"Those who suffer the disease (AIDS) become the victims of life-threatening pneumonia, other serious infections, and a rare skin cancer called Kaposi's sarcoma." (Thomas page 196)
"Acquired immune deficiency syndrome, commonly referred to as AIDS, is a disease that destroys the body's immune system. It does this by attacking helper T cells, which play an essential role in fighting illness. With the immune system disabled, an AIDS patient will usually die from an illness, called a secondary disease, that the body could have fought off successfully if its immune system were intact. AIDS was first identified in the 1980s, and scientists still do not understand many things about how the disease works." (Time-Life, page 136)
"In people with AIDS (acquired immunodeficiency syndrome), the normal ratio of helper to suppressor T-cells is disturbed. The AIDS virus attacks helper T-cells preventing them from carrying out one of their regular duties-to activate the immune system when a threat arises. This breakdown in normal communication between immune cells leaves the body virtually undefended. Those who suffer the disease become the victims of life-threatening pneumonia, other serious infections, and a rare skin cancer called Kaposi's sarcoma." (Thomas, M.D., page 196)
"When healthy, the immune system can fight off most of the viruses, bacteria, and other pathogens that invade the body. When the AIDS virus infects the body, the helper T cells are destroyed, resulting in a weakening of the immune system...As the immune system breaks down, the body becomes increasingly susceptible to secondary diseases, such as pneumonia, that it is too weak to fight off. These are the diseases that usually kill AIDS patients." (Time-Life, page 137)
"The HIV consists of genetic material surrounded by a coating of proteins and lipids. Unlike most viruses, the AIDS virus contains no DNA, only RNA. Such viruses are called retroviruses. As the HIV invades helper T cells, it uses an enzyme called reverse transcriptase to convert its RNA into DNA. The new DNA then instructs the T cell to duplicate the virus...Once invaded, the helper T cell dies through a process that is not understood." (Time-Life, pages 136-137)
"Upon entering the body, the AIDS virus attaches itself to a helper T cell and then injects its RNA and reverse transcriptase into the T cell...With the help of the reverse transcriptase, the cell then produces viral DNA, using the RNA as a blueprint...The newly produced viral DNA forms a ring and proceeds to penetrate the nucleus of the helper T cell...Once inside the T cell's nucleus, the viral DNA becomes an inextricable component of the immune cell's genetic material...Following instructions from the DNA, the T cell produces AIDS RNA, reverse transcriptase, and the ingredients of the virus' coat...The viral ingredients that are produced by the invading DNA assemble themselves to become new AIDS viruses...Each new virus leaves the helper T cell in search of a new host cell, further weakening the immune system...Once invaded, the helper T cell dies through a process that is not yet understood." (Time-Life, pages 136-137)
"MYASTHENIA GRAVIS...This autoimmune disorder is marked by severe muscle weakness and fatigue. This is caused by antibodies that gradually reduce the number of receptors in the fibers that stimulate muscle contractions. A thymus disorder may trigger the disease; the gland is removed and immunosuppressant drugs are often part of the treatment...Muscles affected...Early symptoms include double vision and drooping eyelids as facial muscles become weaker. Throat muscles are affected, so chewing and swallowing can become difficult. The disease may eventually spread to the muscles of the arms and legs." (Clayman, M.D., page 57)
"A recent case described in a medical journal is that of a young boy who was admitted to the hospital in coma from a severe viral pneumonia. He was unconscious, with a high temperature, and was on forced respiration, being unable to breathe unassisted. Everything was done to resuscitate him, but it was quite obvious that he was going to die. The equivalent of a T-cell count was performed; approximately one fifth the normal level was found. He was then given an injection of thymus extract, and within twenty-four hours the entire process had reversed itself. His temperature was down, he was breathing unassisted, and he was conscious. This is the kind of dramatic recovery we are going to see more and more as accurate testing of thymus function and administration of thymus extract, when indicated, become routine in medical practice, as I am sure it will in the next five or ten years. As one of the most eminent workers in the field has said, "The second golden age of 'thymology' is just beginning." (Diamond, pages 10-11)
When the AIDS virus infects the body, the helper T cells are destroyed, resulting in a weakening of the immune system. As the immune system breaks down, the body becomes increasingly susceptible to secondary diseases, such as pneumonia, that it is too weak to fight off. These are the diseases that usually kill AIDS patients." (Time-Life, page 137)
"Those who suffer the disease (AIDS) become the victims of life-threatening pneumonia, other serious infections, and a rare skin cancer called Kaposi's sarcoma." (Thomas, M.D., page 196)
"In a human being or an animal in which the thymus gland has been removed or destroyed, there is a loss in effectiveness of the immune mechanisms of the body that guard against infection and cancerous growth." (Diamond, M.D., page 9)
"The thymus gland, then, prepares the T cell to do its work--to distinguish self from not self, friend from foe, and to destroy foreign cells. This role, called immunological surveillance, is directly concerned with resistance to infections and cancer." (Diamond, M.D., page 10)
"The viruses that cause infections are smaller than bacteria and can pass through the smallest cellular filters of the body. When viruses enter the body, they live on the body's cell enzymes. Viral infections are characterized by fever, headaches, muscular aching, and chills. The common cold is a viral infection, as are some forms of croup, mononucleosis, influenza, polio, tonsillitis, infectious hepatitis, encephalitis, measles, some bladder infections, and asthma. Drugs relieve only the symptoms—they do not kill the virus. Antibiotics are not effective against viral infections; they kill bacteria but not the virus. When a viral infection gets out of hand and bacterial complications set in, antibiotics help. The body's defense system reaction against these infections is the same for all viral infections, no matter what organ is affected....NUTRIENTS...SUPPLEMENT...Important...Raw thymus...SUGGESTED DOSAGE...As directed on label...COMMENTS...Important in immune function, stimulating the thymus gland." (Balch, M.D., page 309)
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