- Non-specific immunity provides the first line of defense against infection. Non-specific immune responses are directed towards a wide range of pathogens, for example, the epithelium provides a physical barrier to the entry of pathogens in addition to producing other antimicrobial factors. Specific immunity takes some time to develop. It allows for a response directed towards a specific antigen. Innate immunity is nonspecific. It provides the first line of defense against infection. Its components include macrophages and neutrophils; barriers like skin, and antimicrobial substances synthesized by the body. Acquired immunity is highly specific. It involves antigen processing and presentation, which induces the production of antibodies specific to the antigen. Active immunity occurs when an antigen introduced into the body stimulates an immune response, i.e. production of antibodies against the antigen. Passive immunity is when preformed antibodies are introduced into the body. For example, during pregnancy, the mother’s antibodies cross the placenta to the fetus to protect it from infection.
- Once in the lymphatic vessels, lymph flows into lymph nodes. The vessels from the lymph nodes merge to form large lymphatic trunks. Lymphatic trunks are named according to the region of the body they serve. They join to form collecting ducts – the right lymphatic duct and the thoracic duct, which join the subclavian veins. Lymph contains clotting factors, proteins, water-insoluble fats and lymphocytes. As lymph passes through the lymph nodes, potentially harmful materials are filtered and immune responses mounted by macrophages and lymphocytes. The macrophages present the pathogens to T-lymphocytes, which become activated and induce an immune response.
- T-lymphocytes synthesize and secrete cytokines, which enhance the responses of other cells to antigens. They become activated through interaction with an antigen presenting cell displaying a foreign antigen. Memory T-cells ensure a quicker response in case of future exposure to the same antigen. B-cells differentiate into plasma cells that synthesize and produce immunoglobulins. Immunoglobulins are transported in the body to react to specific antigens. In specific immunity, the response to the first exposure to an antigen is slower because it takes some time for macrophages to process and present the antigens to T-cells and activate them to differentiate into memory T-cells. During the second and subsequent exposure to the same antigen, memories T-cells ensure a faster immune response.
- Immune disorders may be due to a defect in one or more of the immune system components. For example, impaired antibody production may result to agammaglobulinemias – deficiency in antibodies in blood. An autoimmune disorder occurs when the body produces autoantibodies that react with the body’s tissues, for example rheumatic diseases. Immune deficiency disorders cause recurrent infections because the body is unable to mount an effective immune response to the infectious agent. They may either be primary (congenital), for example, Wiskott-Aldrich syndrome, or secondary (acquired), for example HIV infection.
- The rise in body temperature above normal range during a disease is fever. It plays an important part in the defense against infection. The rise in temperature has been shown to: increase leukocyte mobility; increase T-cell proliferation; decrease the effects of endotoxins, and enhance phagocytosis by leukocytes. Fever is normally self-limiting and rarely life threatening. However, cases of extreme fever may occur. Hyperpyrexia – body temperature equal to or above 41.5 º C, is a medical emergency associated with infections such as enteroviruses and rubeola. It can cause brain damage.
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Kindt, T. J., Goldsby, R. A., Osborne, B. A., & Kuby, J. (2007). Kuby Immunology. New York: W.H. Freeman.
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