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Specific Defenses The Immune System Definitions Innate (nonspecific) Defenses against any pathogen Immunity Specific antibody and lymphocyte response to an antigen Antigen (Ag) A substances that causes the body to produce specific antibodies or sensitized T cells Antibody (Ab) Proteins made in response to an antigen Terminology Serology Study of reactions between antibodies and antigens Antiserum because Generic term for serum it contains Ab Globulins Serum proteins Gamma () globulin Serum fraction containing Ab Serum Proteins Figure 17.2 Immunity Types Acquired immunity Developed during an individual's lifetime Humoral immunity by Involves Ab produced B cells Cell-mediated immunity Involves T cells Acquired Immunity Naturally acquired active immunity Naturally acquired passive immunity Transplacental or via colostrum Artificially acquired active immunity Resulting from infection Injection of Ag (vaccination) Artificially acquired passive immunity Injection of Ab Antigenic Determinants Antibodies recognize and react with antigenic determinants or epitopes. Figure 17.3 Haptens Figure 17.4 Antibody Structure Figure 17.5a-c IgG antibodies Monomer 80% of serum antibodies Fix complement In blood, lymph, intestine Cross placenta Enhance phagocytosis; neutralize toxins & viruses; protects fetus & newborn Half-life = 23 days IgM antibodies Pentamer 5-10% of serum antibodies Fix complement In blood, lymph, on B cells Agglutinates microbes; first Ab produced in response to infection Half-life = 5 days IgE antibodies Monomer 0.002% of serum antibodies On mast cells and basophils, in blood Allergic reactions; lysis of parasitic worms Half-life = 2 days Clonal Selection Figure 17.8 Clonal Selection Bone marrow gives rise to B cells. Mature B cells migrate to lymphoid organs. A mature B cells recognizes epitopes. Self-tolerance Body doesn't make Ab against self Clonal deletion The process of destroying B and T cells that react to self antigens The Results of Ag-Ab Binding Figure 17.9 Antibody titer: Is the amount of Ab in serum Figure 17.10 Monoclonal Antibodies Hybridomas are produced by fusing a cancer cell with an Ab-secreting plasma cells The hybridoma cell culture is immortal and produces monoclonal Abs (Mabs) Immunotoxins: Mabs conjugated with a toxin to target cancer cells Chimeric Mabs: Genetically modified mice that produce Ab with a human constant region Humanized Mabs: Mabs that are mostly human, except for mouse antigen-binding Monoclonal Antibodies Figure 17.11 Immune system cells communicate via cytokines Interleukin-1 Interleukin-2 NK cells Interleukin-12 cells -Interferon Chemokines Stimulates TH cells Activates TH, B, TC, and Differentiation of CD4 Increase activity of macrophages Cause leukocytes to move to an infection Cell-Mediated Immunity Specialized lymphocytes, mostly T cells, respond to intracellular Ags After differentiating in the thymus, T cells migrate to lymphoid tissue T cells differentiate into effector T cells when stimulated by an Ag Some effector T cells become memory cells Pathogens entering the gastrointestinal or respiratory tracts pass through: M (microfold) cells in Peyer's patches which contains Dendritic cells which are antigenpresenting cells and T cells Dendritic cells present antigens Figure 17.12 T Cells Helper T Cells (CD4, TH) TH1 Activate cells related to cell-mediated immunity TH2 Activate B cells to produce eosinophils, IgM, and IgE Cytotoxic T Cells (CD8, TC) Destroy target cells with perforin Helper T Cells Figure 17.13 Cell-mediated Cytotoxicity Figure 17.14 Nonspecific Cells Activated macrophages: Macrophages stimulated by ingesting Ag or by cytokines Natural killer cells: Lymphocytes that destroy virus-infected cells, tumor Figure 17.15 T-independent Antigens Figure 17.16 Antibody-Dependent CellMediated Cytotoxicity Figure 17.18