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Advanced Biology Chapter 22 Nonspecific Body Defenses and Immunity Nonspecific Specific – Innate – Adaptive Intact skin and mucosa Phagocytes Other cells (inflammatory) Specific Defense B Cells and T Cells Functional No System Organs Trillions of Cells Resistance to Disease Nonspecific Specific Keratin provides a barrier – resistant to weak acids/bases and bacterial toxins Acidic – pH 3-5, inhibits bacterial growth; sebum contains chemicals toxic to bacteria Stomach – concentrated HCl and protein digesting enzymes Saliva and lacrimal fluid contains lysozyme which destroys bacteria Sticky mucus traps microorganisms MACROPHAGES Derived from monocytes Free MAC wander all over Kupffer cells -liver Alveolar cells – Lungs Permanent residents WBC that can phagocytize Neutrophils release defensins – kills everything around it, including itself WBC Defend against parasitic worms by surrounding it and discharging enzymes Some bacteria can replicate inside MACs, MACs are stimulated to release other chemicals (Nitric oxide) Police the body Checks markers – releases cytolytic chemicals Prevent Spread of damaging agents Dispose of cell debris Set stage for repair Enhance the body’s nonspecific defenses by attacking microorganisms or hinder their ability to reproduce Classical – Binding of antibodies Alternative – Certain protein factors are initiated Convergence on C3, Splitting it, C3a, C3b. Initiates events that cause lysis, promotes phagocytosis and enhances inflammation Message to tell other cells there is a virus Those cells synthesize “PKR” which interferes with viral replication Pyrogens Pyro – fire Causes liver/spleen to retain zinc/iron Helps speed up metabolic rate of cells Can denature bacterial enzymes Advanced Biology Chapter 22 Specific Body Defenses: Immunity Immune Response Good To mount an immune response is expensive. Lots of energy is required. Being specific, energy is only expended when necessary. Study of Immunity Antigen-Specific Systemic Memory Humoral (Antibodymediated) Cellular (Cell-mediated) Intruders Not self Immunogenicity – stimulate the proliferation of specific lymphocytes and antibody production Reactivity – Ability to react with lymphocytes or antibodies Part of antigen that is immunogenic Binds to it Self-antigen Major Histocompatibility Complex (MHC) Class I MHC – All body cells Class II MHC – Immune Response Cells Antigen (APC) Presenting Cells B Lymphocytes (Humoral) T Lymphocytes (Cell mediated) To be able to recognize a specific antigen Eliminates them Before meeting antigen It is in your genes An antigen only determines which B or T cell will proliferate and attack Engulfs antigen, shows it to a T cell Advanced Biology Chapter 22 Humoral Immune Response Not a game show st 1 Encounter b/w immunocompetent lymphocyte and invading antigen 3 to 6 Days Takes time for B cells to differentiate 2ndry much faster, more prolonged and more effective. 2-3 day response See pg 775 The capacity to produce a powerful 2ndry humoral response When B cells encounter antigens and produce antibodies against them Naturally acquired: During bacterial & viral infections Artificially acquired: Through vaccine Dead or attenuated (living but weakened) pathogens Spare us from most of the symptoms Provide functional antigenic determinates No memory is established Fetus to mother Immunoglobulins IgD – Attaches to B cells, activates B cells IgM – Large, pentamer shape. Antigen receptive, st 1 Ig released during primary response. Fixes and activates complement IgG – Most abundant – 7585%. Crosses placenta, protects against bacteria, viruses and toxins. Fixes complement. IgA – Dimer (2), found in body secretions, helps prevent attachment of pathogens to epithelial cells IgE – Stem region is bound to mast cells and basophils (allergies) Antigen-Antibody complexes Complement Neutralization – blocks specific sites on viruses and bacteria Agglutination – Clumping of cells Precipitation – not rain. Antigen molecules, not cells, are clumped together. See page 780. Advanced Biology Chapter 22 Cell-Mediated Immune Response Microorganisms that slip inside body cells Trying to avoid immune system CD4 = T4, Helper Ts CD8 = T8, Cytotoxic Ts Through processed parts on an APC Provide means for signaling to immune system cells that infectious microorganisms are hiding in body cells Step 1: Antigen Binding T cell antigen receptors, TCRs, bind to an antigen-MHC protein complex Helper Ts bind to MHC II – w/help of APC Cytotoxic Ts bind to MHC I – needs no APC Step 2: Costimulation If bound to right costimulator (protein, chemicals), stimulation (proliferation) occurs. W/O right match, T cell activity is stopped Mediators involved in cellular immunity Lymphokines – released by activated T cells Monokines – secreted by MACs Interleukin 1 & 2 – IL 1 released by MACs tells T cells to liberate IL 2, which encourages T cells to divide more rapidly. Tumor Necrosis Factor (TNF) – enhances nonspecific cell killing Perforin/lymphotoxin are cell toxins that T cells can release. Lethal Hit. Gamma Interferon – enhance killing power of MACs Regulatory cells Interact with B cells Major function is to chemically or directly stimulate proliferation of other T cells and B cells that have already become bound to antigen W/O helper Ts, there is no immune response!! Killer T cells They can directly attack and kill other cells Main target is virus infected cells, also tissue cells that have been infected, parasites, cancer cells, foreign cells introduced by blood transfusions or organ transplants Help stop immune response after antigen has been destroyed Promote reactions allergic