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Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 1 Module 2 The Immune System 1. Competency ............................................................................................................ 2 2. Learning Objectives ................................................................................................. 2 3. Introduction.............................................................................................................. 2 4. Immune Defense ..................................................................................................... 2 5. Lymphatic System ................................................................................................... 5 6. Development of the fetal and neonatal immune system ........................................... 6 7. Summary ................................................................................................................. 6 8. Required Reading.................................................................................................... 7 9. References .............................................................................................................. 7 10. Quiz ......................................................................................................................... 7 11. Quiz Answers .......................................................................................................... 9 Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 2 1. Competency Demonstrate a general understanding of the immune system. 2. Learning Objectives By the end of this module you will be able to: Compare and contrast innate and adaptive immunity. Differentiate between passive and active immunity. Describe the lymphatic system. Describe the development of the fetal and infant immune system. 3. Introduction Knowledge of the basic functions of the immune system is useful in order to understand how vaccines work and so you can provide recommendations on their use. 4. Immune Defense 4.1 Overview The body is protected from infectious agents and other harmful substances by a variety of cells and molecules that make up the immune system. Immunity is the ability of the human body to tolerate the presence of material indigenous to the body (self), and to eliminate foreign (non-self) material. The discriminatory ability provides protection from infectious disease, since most agents or associated toxins are identifies as foreign by the immune system. 4.2 Immune Response to an Infection The immune response responds at the site of the infection and at the lymph nodes away from the infection. We can understand the immune response by following the course of an infection. Barriers: Most pathogens are kept outside of the body by protective mechanisms such as tears, stomach acid and cilia Pathogen enters the body: When there is an injury to tissue, bacteria or viruses can enter the tissue and cause an infection “Innate” cells respond Cells, such as macrophages and dendritic cells, in the tissues are specialized in engulfing (phagocytosis) the invader. Dendritic cells get to work Dendritic cells engulf the pathogen, present the antigen on their cell surface and then travel to the lymph node. Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 3 T-Cells and B-Cells “adapt” to presenting antigen In the lymph node the T-Cells are activated by the dendritic cells. The T-Cells activate the B-Cells to make antibodies “Adaptive Immunity” kills invader The T-Cells and antibodies return to the site of infection and help kill the pathogen. 4.3 Immune System To understand how vaccines work, you need to know how the immune system learns to recognize and eliminate micro organisms that cause infectious disease. Use Figure 1 and the following document to learn more about each component of the immune system: Nova Scotia Immunization Manual: http://www.gov.ns.ca/hpp/cdpc/info-for-professionals.asp Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 4 Figure 1: Immune Defense ANTIGENS Infection Physiologic And Chemical Immunization IMMUNE DEFENSE 1 Innate Immunity Cellular/Phagocytosis Active Immunity Passive Immunity Molecular Injected IMMUNE DEFENSE 2 Maternal Adaptive Immunity Cells T cells Cellular (cell mediated) immunity T Cell DEPENDENT Response B cells Humoral immunity T Cell INDEPENDENT Response Antibodies IgM IgG IgA IgE IgD Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 5 5. Lymphatic System The cells of the immune system are transported throughout the body via the lymphatic circulatory system. Lymph bathes the tissues of the body, and the lymphatic vessels collect and move it eventually back into the blood circulation. Lymph nodes are found throughout the lymphatic vessels and provide meeting areas for the immune system cells. The lymphatic system contains the following: Primary Lymphoid Organs: bone marrow, thymus, lymphatic vessels Secondary Lymphoid Organs: lymph nodes, spleen Figure 2 - Lymphatic System Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 6 6. Development of the fetal and neonatal immune system The development of the immune system occurs early in the fetal development. Newborns (even premature infants) can actively distinguish self from non-self. 6.1 Fetal Development Passive Immunity Active Immunity Passage of maternal antibodies - IgG only B-Cells and T-Cells are present by 14 weeks gestational age (GA) Beginning at 8 weeks gestational age (GA) Relatively sterile environment in utero. Enormous unchallenged immune system capacity. Levels of IgG correlate with GA Low until 20 weeks GA By 40 weeks GA, the IgG doubles that of 32 weeks GA 6.2 Neonatal and Infant Immunity Birth Instant challenge Within hours after birth the gastrointestinal tract is heavily colonized Passive Immunity (maternal antibodies) Active Immunity Circulating placental IgG lasts 6 months or longer B-Cell responses are good. Until two (2) years of age the child’s immune system does not respond well to T-Cell independent antigens (i.e., polysaccharides) Secretory IgA in breast milk and colostrum T-Cells: Responds well to T-Cell dependent antigens (i.e., proteins) 7. Summary The immune system is a complex coordination of organs, cells and proteins. Innate and adaptive immunity work together to recognize self from non-self. Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 7 8. Required Reading Nova Scotia Immunization Manual: http:/www.gov.ns.ca/hpp/cdpc/info-for-professionals.asp 9. References Nova Scotia Immunization Manual: http:/www.gov.ns.ca/hpp/cdpc/info-for-professionals.asp 10. Quiz Question #1 What term is best described as "The first line of defence against anything recognized as non-self"? A. Passive Immunity B. Active Immunity C. Adaptive Immunity D. Innate Immunity Question #2 Antibodies from breast milk are an example of which one of the following immunities? A. Passive Immunity B. Active Immunity C. Adaptive Immunity D. Innate Immunity Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 8 Question #3 Which one of the following is a correct statement regarding IgM? A. The most abundant immunoglobulin making up approximately 80% of all antibodies in serum B. The first immunoglobulin made following antigen exposure and is relatively shortlived C. The only immunoglobulin that reaches the thymus gland and under goes differentiation to become T-Cells D. The main secretory immunoglobulin in breast milk, saliva, tears, and respiratory secretions Question #4 At birth, an infant's immune system is only able to recognize and respond to a limited number of organisms at any one time. A. True B. False Immunization Competency Course - v 1.0 Module 2 - Immune System May 2012 Page 9 11. Quiz Answers Question #1 Answer: D Innate Immunity is the first line of defence against anything recognized as non-self. Question #2 Answer: A Antibodies from breast milk is an example of Passive Immunity. Question #3 Answer: B IgM is the first immunoglobulin made following antigen exposure and is relatively shortlived. Question #4 Answer: False Infants are capable of generating both humoral and cellular immune response to pathogens at the time of birth.