Since each antibody does not act against a variety of

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Since each antibody does not act against a variety of antigens but rather acts only against its specific antigen, it is necessary
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for the immune system to come into contact with the antigen against which the immunization is intended. The recognition of specific molecular portions of each antigen causes the immune system to produce the specific variable portion of the immunoglobulins to attack that antigen. Therefore, to induce active immunization, it is necessary to inoculate the body with small parts of the infectious agent or the entire agent (dead or inactivated). 27. What types of antigenic agents may constitute vaccines? Vaccines can be composed of dead agents of the disease, inactivated agents of the disease, inactivated toxins or fragments of the infectious agent. Examples of some vaccines and their type of antigenic agents are: BCG, inactivated tuberculosis bacilli; the tetanus vaccine, inactivated toxin; the anti-diphtheria, inactivated toxin; antipolio Salk vaccine, dead poliovirus; antipolio Sabin vaccine, attenuated (inactivated) poliovirus. 28. Why doesn't a long lasting vaccine against the common cold yet exist? Viruses that have a high mutation rate, such as the virus that causes the common cold, easily circumvent the action of vaccines against them. After a primary immune response (natural or artificially induced) against the virus, during the next season of infection, new mutant resistant strains appear and the protection obtained by the immune response of the last season is lost. (It can be said that this high mutation rate is a form of “immunization” discovered by these viruses.)
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29. Why are vaccines used in the prevention but not in the treatment of infections? Why can antivenom serums be used in prevention and treatment? Vaccines are not used in the treatment of infections because they depend on the primary immune response, which takes about a week to occur and is not so intense and effective. On the other hand, antivenom serums are inoculated into circulation and are used as an immediate treatment because they are made of a large amount of immunoglobulin (antibodies) which are potent against their respective specific venom. 30. What is a DNA vaccine? A DNA vaccine, or DNA vaccination, is a vaccination technology based on genetic engineering. In DNA vaccination, a recombinant plasmid (vector) containing the gene of a specific antigen that is part of a given pathogenic agent is inserted into the cells of the individual to be immunized. These cells then begin to produce the antigen that triggers the primary immune response and, theoretically, the individual becomes immunized against that antigen. Autoimmunity 31. What is the name given to conditions in which the immune system of an individual is the agent of
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diseases? What are some examples of these conditions? Diseases caused by the action of an individual's own immune system are called autoimmune diseases. Autoimmune diseases appear when the immune system produces antibodies or defense cells that attack cells, tissues and organs of its own body. The attacked cells or tissues are wrongly recognized as antigens by the immune system. Rheumatoid arthritis, lupus, scleroderma, vitiligo, pemphigus, type I diabetes mellitus, Crohn's disease (chronic inflammation of the gut), myasthenia gravis, Graves' disease, Hashimoto's disease, etc., are all examples of autoimmune diseases.
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