Adaptive Immunity Nursing 240
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This 3 page Class Notes was uploaded by Jordan Smith on Tuesday April 5, 2016. The Class Notes belongs to Nursing 240 at Southern Illinois University Edwardsville taught by Dr. Jo Anne Pritchett in Spring 2016. Since its upload, it has received 19 views. For similar materials see Pathophysiology N240 in Nursing and Health Sciences at Southern Illinois University Edwardsville.
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Date Created: 04/05/16
Chapter 6/Module 5 Adaptive Immunity & Third Line of Defense Adaptive (Acquired) Immunity • Known as immune response or immunity • Develops more slowly & is specific compared to the inflammatory response (non specific) & has memory • Two purposes: destroys infectious microorganisms that are resistant to inflammation AND provides longterm effective protection against future exposure to the same microorganism Immune System • Identifies substances that are foreign or “nonself” that are called antigens • Antigens are on infectious agents (viruses, bacteria, fungi, parasites) AND on non infectious substances from the environment such as pollen, foods, & bee venoms OR on drugs, vaccines, transfusions, & transplanted tissues Antigens & Immunogens • Antigen – molecule or molecular fragment (protein or carbohydrate) that can bind with antibodies or antigen receptors on B & T cells • Immunogen – molecule that will induce an immune response • All immunogens are antigens but not all antigens are immunogens. • Example: urushiol is a toxin found in poison ivy & is a very small antigen (hapten) but is not immunogenic due to its small size UNTIL it combines with larger carrier molecules • Antigens that induce an allergic response are also called allergens Products of Adaptive Immune Response • Serum proteins – immunoglobulins (Ig) or antibodies AND a type of blood cell called a lymphocyte • Before birth humans produce large amounts of T lymphocytes produced by the thymus gland & B lymphocytes produced by the bone marrow that can recognize almost any foreign antigen in the environment • Each individual T or B cell specifically recognizes only one particular antigen but the total of lymphocytic specificities may be in the millions • Two arms of immune response – humoral & cellular immunity Humoral Immunity (B Cells) • Antibodies are proteins produced by plasma cells that mature from B lymphocytes in response to an antigen. • Circulate in the blood and bind to antigens on infectious agents. • This process can cause direct inactivation of the microorganism OR activation of a variety of inflammatory mediators that will destroy the pathogen Classes of Immunoglobulins IgG • IgG – most abundant class (85%) of immunoglobulins & account for most of the protective activity against infections • IgG is major class of antibody found in fetal & newborn blood • Four subclasses: IgG1, IgG2, IgG3, IgG4 Classes of Immunoglobulins IgA & IgM • IgA1 – found mostly in the blood; plays critical role in mucosal immunity • IgA2 – found mostly in body secretions (called secretory IgA); tears, saliva, sweat, colostrum, mucus • IgM IgM – largest immunoglobulin & is first antibody produced during the initial or primary response to antigens Classes of Immunoglobulins IgD & IgE • IgD – low concentrations in blood; primary function as an antigen receptor on surface of early B cells • IgE – low concentrations in blood; has very specialized functions as a mediator of many common allergic responses & in defense against parasitic infections. Direct Action of Antibodies • Affect infectious agents or their toxic products by neutralization (inactivating or blocking the binding of antigens to receptors) • By agglutination (clumping insoluble particles that are in suspension) • By precipitation (making a soluble antigen into an insoluble precipitate) Indirect Action of Antibodies • Protective by interaction with or activation of the complement system components of inflammation Cellular/CellMediated Immunity (Tissue) • T cells are a subset of lymphocytes that undergo differentiation during an immune response & develop into several subpopulations of effector T cells that have an “effect” on other cells. • Tcytotoxic (Tc) cells attack & kill targets directly (viruses, cancers) • Others may develop into T cells that stimulate other leukocytes through cell to cell contact or through the secretion of cytokines. CellMediated Immunity Con’t • T lymphocytes – large spectrum of cell types & function that include: • Tcytotoxic (Tc) that attack antigens directly & destroy cells bearing antigens such as viruses • Thelper (Th) that regulates both cellregulated & humoral immune responses • T cells are important in protection against viruses, tumors, & pathogens that are resistant to killing by neutrophils & macrophages Bs & Ts Active & Passive Immunity • Active immunity is produced by an individual either after natural exposure to antigens or after immunization. • Passive immunity does NOT involve the host’s immune response at all, but occurs when preformed antibodies or T cells are transferred from a donor to the recipient. Example: maternal antibodies that cross the placenta to the fetus. Clonal Diversity – First Phase of Immune Response • Fetal production of large population of T & B cells that have the capacity to recognize foreign antigens – generation of clonal diversity • Process mostly occurs in primary lymphoid organs of thymus and bone marrow resulting in differentiation of lymphoid stem cells into B & T lymphocytes that can react against almost any antigen Clonal Selection – Second Phase of Immune Response • Antigens initiate clonal selection – process that involves a complex interaction among cells in secondary lymphoid organs such as the spleen, lymph nodes, adenoids, tonsils, Peyer patches in intestine, and appendix • Most antigens must be processed because they can’t directly react with the immune system cells – they have to be presented to the immune cells & that is done by antigenprocessing cells such as dendritic cells or macrophages Primary Immune Response • After a single exposure to most antigens there is a latent period/lag phase during which antigen processing & B cell differentiation & proliferation occur • After approx. 5 – 7 days IGM antibody is detected in the circulation • The lag time is necessary for the process of clonal selection, initial production of IgM, followed by production IgG against the same antigen • The amount of antibody in a serum sample is called the titer; the higher the titer the higher the circulating antibody Secondary Immune Response • Second (later) challenge by the same antigen results in more rapid production of a larger amount of antibody than the primary response that is the result of memory cells that do not require further differentiation • IgG is predominant • If antigen is in the form of a vaccine (e.g. polio) or through natural infection (e. g. rubella) the level of IgG may remain elevated for years.
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