Microbiology

Microbiology Study Guide

©2018 of 132 The next category of antibody is IgA, which is developed and found in the external secretions of the body, like mucosal surfaces of the respiratory, gastrointestinal, and urogenital tracts (tears, saliva, urine, tears, and colostrum). The mother’s milk also contains this category of antibody, which augments the antibodies in the newborn. IgA is responsible for defending infections at the surface of the body. The structure of IgA is comprised of two units of antibodies, which are connected by a J chain at one end and a secretory component at the other. IgD is the fourth antibody category and is one of the receptors. It resides in the serum of the body and exists in very small quantities. IgD even exists at the surface of the immune cells of B-lymphocytes. The fifth and the last formof antibody is IgE, which is a vital substance in dealing with hypersensitivity reactions, like anaphylaxis. They exist in very minute quantities in the serum of the body. These antibodies react with the antigen determinants and then neutralize the antigen; they combat the dissemination of infection in the body. These antibodies react with the structure of bacteria, like surface flagella, pilli, or capsules of bacteria, and activate phagocytosis. Upon reaction with the virus, the antibodies do not allow the virus cells to attach themselves to the host to replicate and infect the host. This reaction sets off the complement system, which accelerates phagocytosis. When reacting with the toxin molecules, antibodies help neutralize toxins and stop the damage to bodily tissues. There are two general pathways for the complement activity: the classical pathway and the alternative pathway. The classical pathway deals with a highly specific immune system. It is initiated when antibodies unite with antigens and stimulate the complement system. The alternative pathway involves the non-specific immune system. It is initiated by tumors, bacterial cell walls, and various microorganisms. It is also called the properdin pathway, named after the protein operating within it. It is a slower, less specific method of eliminating gram-negative bacteria and viruses. Types of Immunity Immunity can be distinguished between innate immunity and acquired immunity. The immunity that is present in the body from the time of birth is known as innate immunity; the immunity that is activated due to the immune system is known as acquired immunity. Innate immunity consists of a number of non-specific factors that become activated at the time of infection and disease. The acquired immunity can further be divided into two categories: active immunity and passive immunity. Active immunity lasts for a long time and is acquired when antibodies are produced by the body. This immunity stimulates the immune system and it generally takes a few hours to become activated. Active immunity can also be divided further into naturally acquired active immunity and artificially acquired active immunity. When the body is exposed to the stint of illness or entry by a microorganism, irrespective of the occurrence of the disease, the immunity that is developed is known as naturally acquired active immunity. This immunity operates at the natural scheme of events, and during this phase, the B- lymphocytes and plasma cells get activated and operate. Achieve Page 62

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