McKenna's Pharmacology for Nursing, 2e

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P A R T 3  Drugs acting on the immune system

mild response from the immune system and somehow tricks the T cells into allowing it to survive. Viral invasion of cells Viruses are genetic parasites that can survive only by invading a host cell that provides the nourishment nec­ essary for viral replication. Invasion of a cell alters the cell membrane and the antigenic presentation of the cell (the MHC). This change can activate cellular immunity, or it can be so subtle that the immune system’s response to the cell is mild or absent. In some cases, the response activates a cellular immune reaction to normal cells similar to the one that was invaded. This is one theory for the development of autoimmune disease. Autoimmune disease Autoimmune disease occurs when the body responds to specific self-antigens to produce antibodies or cell- mediated immune responses against its own cells. The cause of autoimmune disease is not known, but theories speculate that (1) it could be a result of response to a cell that was invaded by a virus, leading to antibody pro­ duction to similar cells; (2) production of autoantibodies is a normal process that goes on all the time, but in a state of immunosuppression the suppressor T cells do not suppress autoantibody production; or (3) there is a genetic predisposition to develop autoantibodies. Transplant rejection With the growing field of organ transplantation, more is being learned about the reaction to foreign cells that are introduced into the body. Typically, self-transplantation, or autotransplantation, results in no immune response. All other transplants produce an immune reaction. Therefore, matching a donor’s HLA markers as closely as possible to those of the recipient for histocompatibil­ ity is essential. The more closely the foreign cells can be matched, the less aggressive the immune reaction to the donated tissue will be. CHAPTER SUMMARY ■■ The body has several defence mechanisms in place to protect it from injury or foreign invasion: the skin, mucous membranes, normal flora, gastric acid, and the inflammatory and immune responses. ■■ The inflammatory response is a general response to any cell injury and involves activation of Hageman factor to stimulate the kinin system and release of histamine from injured cells to generate local inflammatory responses. ■■ The clinical presentation of an inflammatory reaction is heat (calour), redness (rubor), swelling (tumour) and pain (dolour).

■■ The inflammatory response is a non-specific reaction to any cellular injury and involves the activation of various chemicals and neutrophil activity. The immune response is specific to an antigen or protein that has entered the body and involves B cells, antibodies and T cells. ■■ Several types of T cells exist: effector or cytotoxic T cells, helper T cells and suppressor T cells. Effector or cytotoxic T cells immediately destroy foreign cells. Helper T cells stimulate the immune and inflammatory reactions. Suppressor T cells dampen the immune and inflammatory responses to conserve energy and prevent cellular damage. ■■ B cells are programmed to recognise specific proteins or foreign antigens. Once in contact with that protein, the B cell produces antibodies (immunoglobulins) that react directly with the protein. ■■ Reaction of an antibody with the specific receptor site on the protein activates the complement cascade of proteins and lyses the associated protein or precipitates an aggressive inflammatory reaction around it. ■■ Other chemicals are involved in communication among parts of the immune system and in local response to invasion. Any of these chemicals has the potential to alter the immune response. ■■ The T cells, B cells and inflammatory reaction work together to protect the body from invasion, limit the response to that invasion and return the body to a state of homeostasis. ■■ Problems that occur within the immune system include the development of neoplasms, viral invasions of cells that trigger immune responses, autoimmune diseases and rejection of transplanted organs. Knowing your strengths and weaknesses helps you to study more effectively. Take a PrepU Practice Quiz to find out how you measure up! ONLINE RESOURCES An extensive range of additional resources to enhance teaching and learning and to facilitate understanding of this chapter may be found online at the text’s accompanying website, located on thePoint at http://thepoint.lww.com. These include Watch and Learn videos, Concepts in Action animations, journal articles, review questions, case studies, discussion topics and quizzes. Abbas, A., Lichtman, A. H. & Pillai, S. (2014). Basic Immunology: Functions and Disorders of the Immune System (4th edn). Philadelphia: Elsevier Saunders. Barrett, K. E. & Ganong, W. F. (2012). Ganong’s Review of Medical Physiology (24th edn). New York: McGraw-Hill. Doan, T. (2013). Lippincott’s Illustrated Reviews: Immunology (2nd edn). Philadelphia: Lippincott Williams & Wilkins. Hall, J. (2011). Guyton and Hall Textbook of Medical Physiology (12th edn). Philadelphia: Saunders. BIBLIOGRAPHY