Immunology
Transcript: IMMUNE SYSTEM An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. The proper targets of your immune system are infectious organisms: bacterias, fungus, Parasites and viruses. This set of unique markers on human cells is called the major histocompatibility complex (MHC). There are two classes: MHC Class I proteins, which are on all cells, and MHC Class II proteins, which are only on certain specialized cells. Markers of Non-Self Any non-self substance capable of triggering an immune response is known as an antigen. An antigen can be a whole non-self cell, a bacterium, a virus, an MHC marker protein or even a portion of a protein from a foreign organism. The distinctive markers on antigens that trigger an immune response are called epitopes. When tissues or cells from another individual enter your body carrying such antigenic non-self epitopes, your immune cells react. This explains why transplanted tissues may be rejected as foreign and why antibodies will bind to them. Markers of Self: Major Histocompatibility Complex For example, when the immune system of a patient receiving a kidney transplant detects a non-self "tissue type," the patient's body may rally its own immune cells to attack. Every cell in your body is covered with these MHC self-marker proteins, and--except for identical twins--individuals carry different sets. MHC marker proteins are as distinct as blood types and come in two categories--MHC Class I: humans bear 6 markers out of 200 possible variations; and MHC Class II: humans display 8 out of about 230 possibilities. Organs of the Immune System The organs of your immune system are positioned throughout your body. They are called lymphoid organs because they are home to lymphocytes--the white blood cells that are key operatives of the immune system. Within these organs, the lymphocytes grow, develop, and are deployed. The cells of the adaptive immune system are special types of leukocytes, called lymphocytes. B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow. B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response. Killer T cell are a sub-group of T cells that kill cells that are infected with viruses (and other pathogens), or are otherwise damaged or dysfunctional. As with B cells, each type of T cell recognises a different antigen. Helper T cells regulate both the innate and adaptive immune responses and help determine which types of immune responses the body will make to a particular pathogen. These cells have no cytotoxic activity and do not kill infected cells or clear pathogens directly. They instead control the immune response by directing other cells to perform these tasks. Nutrition and diet The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory, where each pathogen is "remembered" by a signature antigen, should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. Killer T cells yö T cells Adaptive Immune System A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen. This antigen/antibody complex is taken up by the B cell and processed by proteolysis into peptides. Your immune cells recognize major histocompatibility complex proteins(MHC) when they distinguish between self and non-self. An MHC protein serves as a recognizable scaffold that presents pieces (peptides) of a foreign protein (antigenic) to immune cells. An empty "foreign" MHC scaffold itself can act as an antigen when donor organs or cells are introduced into a patient's body. These MHC self-marker scaffolds are also known as a patient's "tissue type" or as human leukocyte antigens (HLA) when a patient's white blood cells are being characterized. The functioning of the immune system, like most systems in the body, is dependent on proper nutrition. It has been long known that severe malnutrition leads to immunodeficiency. Overnutrition is also associated with diseases such as diabetes and obesity, which are known to affect immune function. More moderate malnutrition, as well as certain specific trace mineral and nutrient deficiencies, can also compromise the immune response. Specific foods may also affect the immune system; for example, fresh fruits, vegetables, and foods rich in certain fatty acids may foster a healthy immune system. Likewise, fetal undernourishment can cause a lifelong impairment of the immune system. In traditional medicine, some herbs are believed to stimulate the immune system, such as echinacea, licorice, ginseng, astragalus, sage, garlic, elderberry, and hyssop, as well as honey although further research is needed to understand their mode of action. Cells destined to become immune cells,
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