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Chapter 13 Body Defense Mechanisms Suggested Lecture Presentation Susan Capasso, Ed.D., CGC St. Vincent’s College Copyright © 2009 Pearson Education, Inc. Body Defense Mechanisms The body’s defense system targets pathogens and cancerous cells The body has three lines of defense The immune system distinguishes self from nonself The immune system mounts antibodymediated responses and cell-mediated responses Copyright © 2009 Pearson Education, Inc. Body Defense Mechanisms The cell-mediated immune response and the antibody-mediated immune response have the same steps Immunity can be active or passive Monoclonal antibodies are used in research, clinical diagnosis, and disease treatment The immune system can cause problems Copyright © 2009 Pearson Education, Inc. The Body’s Defense System The body’s defense mechanisms target pathogens and cancerous cells Copyright © 2009 Pearson Education, Inc. The Body Has 3 Lines of Defense The body has three lines of defense Nonspecific 1. Physical and chemical surface barriers 2. Internal cellular and chemical defense Specific 3. Immune response Copyright © 2009 Pearson Education, Inc. The Body Has 3 Lines of Defense Nonspecific defenses First line of defense: Nonspecific physical and chemical surface barriers Second line of defense: Nonspecific internal cellular and chemical defense If pathogen penetrates barriers Copyright © 2009 Pearson Education, Inc. Specific defenses Third line of defense: Immune response If pathogen survives nonspecific internal defenses Figure 13.1 Nonspecific Surface Barriers Physical and chemical barriers The skin Nearly impenetrable Waterproof Resistant to most toxins and enzymes of invading organisms Sweat and oil glands Produce chemicals that slow or prevent the growth of bacteria Copyright © 2009 Pearson Education, Inc. Nonspecific Surface Barriers Physical and chemical barriers (continued) Mucus of the respiratory and digestive tracts Sticky and traps many microbes The lining of the stomach Produces hydrochloric acid and digesting enzymes that destroy pathogens Copyright © 2009 Pearson Education, Inc. Nonspecific Surface Barriers Physical and chemical barriers (continued) Urine Slows bacterial growth with acidity Washes microbes from urethra Saliva and tears Contain lysozyme, an enzyme that kills bacteria Copyright © 2009 Pearson Education, Inc. Nonspecific Surface Barriers Copyright © 2009 Pearson Education, Inc. Figure 13.2 (1 of 2) Nonspecific Surface Barriers Copyright © 2009 Pearson Education, Inc. Figure 13.2 (2 of 2) Nonspecific Internal Defenses The second line of defense Defensive cells Defensive proteins Inflammation Fever Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Table 13.1 Nonspecific Internal Defenses PLAY Animation—The Inflammatory Response Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Defensive cells include neutrophils and macrophages They engulf pathogens, damaged tissue, or dead cells by the process of phagocytosis Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.3 Nonspecific Internal Defenses Eosinophils Attack pathogens that are too large for phagocytosis, such as parasitic worms Get close to the parasites and discharge destructive enzymes that destroy them Natural killer (NK) cells Search out abnormal cells, including cancerous cells, and kill them Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.4 Nonspecific Internal Defenses The body’s non-specific cellular defenses use two types of defensive proteins Interferons Complement system Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Before a virally–infected cell dies, it secretes small proteins called interferons that Attract macrophages and natural killer cells Stimulate neighboring cells to make proteins that prevent the viruses from replicating Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses The complement system A group of proteins that enhance both nonspecific and specific defense mechanisms by Destroying pathogens Enhancing phagocytosis Stimulating the inflammatory response Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.5 (1 of 3) Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.5 (2 of 3) Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.5 (3 of 3) Nonspecific Internal Defenses Inflammatory response destroys invaders and helps repair and restore damaged tissue Redness Heat Swelling Pain Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.6 (1 of 2) Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.6 (2 of 2) Nonspecific Internal Defenses The increased blood flow to damaged tissue stimulates mast cells and basophils to release histamine Increases blood flow by dilating blood vessels and increasing the permeability of the capillaries Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Fluid leaks from the capillaries Causes swelling Blood flow increases Causes redness and warmth Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Fever An abnormally high body temperature caused by pyrogens Chemicals that reset the brain’s thermostat to a higher temperature A moderately higher body temperature helps fight bacterial infections Copyright © 2009 Pearson Education, Inc. Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Figure 13.7 Nonspecific Internal Defenses Copyright © 2009 Pearson Education, Inc. Table 13.1 Specific Immune Responses The third line of defense is the immune system Has specific responses and memory Copyright © 2009 Pearson Education, Inc. Specific Immune Responses Immune response The body’s specific defenses Work together in the recognition and destruction of specific pathogens Have memory Copyright © 2009 Pearson Education, Inc. The Immune System Distinguishes Self from Nonself The body must be able to distinguish a foreign organism or molecule from self MHC markers are found on our own cells and mark them as belonging to us Copyright © 2009 Pearson Education, Inc. The Immune System Distinguishes Self from Nonself Copyright © 2009 Pearson Education, Inc. Figure 13.8 The Immune System Antigens Nonself substances that trigger an immune response Usually large molecules, such as proteins, polysaccharides, or nucleic acids Copyright © 2009 Pearson Education, Inc. The Immune System When an antigen is detected B lymphocytes and T lymphocytes that recognize the antigen are stimulated to divide repeatedly Copyright © 2009 Pearson Education, Inc. The Immune System Some of these cells attack and eliminate the invader Others are stored in a state of suspended animation as a form of memory of the invader Available to attack if there is a reoccurrence Copyright © 2009 Pearson Education, Inc. Antibody-Mediated Responses Antibody-mediated immune responses Defend against antigens that are free in body fluids, including toxins or extracellular pathogens Copyright © 2009 Pearson Education, Inc. Antibody-Mediated Responses B cells use antibodies to neutralize the antigen Copyright © 2009 Pearson Education, Inc. Antibody-Mediated Responses Step 1: Threat Antigen Engulfed Step 2: Detection Macrophage Presents antigen to identify invader and activates helper T cells Step 3: Alert Memory helper T cell Helper T cell Step 7: Continued surveillance Cell divides Cell divides Antibody-mediated response Cell-mediated response Activates Naive B cell Step 4: Alarm Copyright © 2009 Pearson Education, Inc. Activates Effector helper T cell Step 4: Alarm Naive cytotoxic T cell Figure 13.9 (1 of 3) Antibody-Mediated Responses Antibody-mediated response Activates Naive B cell Step 4: Alarm Step 5: Building specific defenses Effector helper T cell Cell divides Plasma cell Step 6: Defense Secretes Memory B cell Step 7: Continued surveillance Memory cells remain and provide a quick response to the antigen in a future encounter Antibodies Targets Pathogens or toxins outside of cells Copyright © 2009 Pearson Education, Inc. Figure 13.9 (2 of 3) Antibody-Mediated Responses B cell Helper T cell Step 4: Alarm The helper T cell stimulates the B cell to begin dividing. B cell Step 5: Building specific defenses The B cell divides and forms plasma cells and memory cells. B cell Memory B cell Plasma cell Copyright © 2009 Pearson Education, Inc. Figure 13.12 (1 of 2) Antibody-Mediated Responses Step 5: Building specific defenses The B cell divides and forms plasma cells and memory cells. B cell Memory B cell Plasma cell Step 6: Defense Plasma cells secrete antibodies specific for that antigen. Plasma cell Antibodies Step 7: Continued surveillance Memory B cells remain and mount a quick response if the invader is encountered again. Memory B cells Copyright © 2009 Pearson Education, Inc. Figure 13.12 (2 of 2) Cell-Mediated Responses Cell-mediated immune responses Involve living cells Protect against cellular threats, including body cells that have become infected and cancer cells Copyright © 2009 Pearson Education, Inc. Cell-Mediated Responses Step 1: Threat Antigen Engulfed Step 2: Detection Macrophage Presents antigen to identify invader and activates helper T cells Step 3: Alert Memory helper T cell Helper T cell Step 7: Continued surveillance Cell divides Cell divides Antibody-mediated response Cell-mediated response Activates Naive B cell Step 4: Alarm Copyright © 2009 Pearson Education, Inc. Activates Effector helper T cell Step 4: Alarm Naive cytotoxic T cell Figure 13.9 (1 of 3) Cell-Mediated Responses Cell-mediated response Effector helper T cell Activates Step 4: Alarm Naive cytotoxic T cell Step 5: Building specific defenses Cell divides Memory cells remain and provide a quick response to the antigen in a future encounter Memory cytotoxic T cell Step 7: Continued surveillance Effector cytotoxic T cell Step 6: Defense Targets Cells infected with intracellular pathogen; cancer cells; cells of organ transplants Copyright © 2009 Pearson Education, Inc. Figure 13.9 (3 of 3) Cell-Mediated Responses Antigen Virus Helper T cell Step 4: Alarm The helper T cell stimulates a naive or memory cytotoxic T cell to begin dividing. Cytotoxic T cell Step 5: Building specific defenses The cytotoxic T cell divides and forms effector cytotoxic T cells and memory cytotoxic T cells. Memory cytotoxic T cell Effector cytotoxic T cell Copyright © 2009 Pearson Education, Inc. Figure 13.14 (1 of 2) Cell-Mediated Responses Step 5: Building specific defenses The cytotoxic T cell divides and forms effector cytotoxic T cells and memory cytotoxic T cells. Memory cytotoxic T cell Effector cytotoxic T cell Step 6: Defense Effector cytotoxic cells cause the target cell to burst and die. In this case, the target cell is a cell infected with a virus that triggered the response. Target cell Perforin T cell membrane Target cell membrane Perforin assembling into pores Step 7: Continued surveillance Memory cytotoxic T cells remain and mount a quick response if the invader is encountered again. Memory cytotoxic T cells Copyright © 2009 Pearson Education, Inc. Figure 13.14 (2 of 2) Cell-Mediated Responses Copyright © 2009 Pearson Education, Inc. Table 13.2 (1 of 2) Cell-Mediated Responses Copyright © 2009 Pearson Education, Inc. Table 13.2 (2 of 2) Cell-Mediated Responses Copyright © 2009 Pearson Education, Inc. Table 13.3 (1 of 2) Cell-Mediated Responses Copyright © 2009 Pearson Education, Inc. Table 13.3 (2 of 2) Cell-Mediated Responses PLAY Animation—Antibody- and Cell-Mediated Immunity Copyright © 2009 Pearson Education, Inc. Immune Response Steps 1. Threat Foreign cell or molecule enters the body 2. Detection Macrophage detects foreign cell or molecule and engulfs it Copyright © 2009 Pearson Education, Inc. Immune Response Steps 3. Alert Macrophages present antigens to helper Tcells to trigger an immune response They are called antigen-presenting cells Copyright © 2009 Pearson Education, Inc. Immune Response Steps Copyright © 2009 Pearson Education, Inc. Figure 13.10 Immune Response Steps 4. Helper T cells activate B cells and T cells to destroy the specific antigen When activated, these cells divide to form clones of cells designed to eliminate a specific antigen from the body Copyright © 2009 Pearson Education, Inc. Immune Response Steps B-cell receptor There is a tremendous variety of B cells. Each B cell has receptors for a different antigen on its surface. B cells This B cell has receptors specific for this particular antigen. Antigen The antigen binds to the B cell with appropriate receptors. The selected B cell divides, producing a clone of cells all bearing receptors specific for that particular antigen. Copyright © 2009 Pearson Education, Inc. Figure 13.11 (1 of 2) Immune Response Steps The selected B cell divides, producing a clone of cells all bearing receptors specific for that particular antigen. Plasma cells produce antibodies specific for this particular antigen. Plasma cells Memory cells remain to bring about a quick response to that antigen in the future. Memory cells Copyright © 2009 Pearson Education, Inc. Figure 13.11 (2 of 2) Immune Response Steps 5. Specific defense mechanism is built B cells form plasma cells that secrete antibodies into the bloodstream that bind to antigens T cells form cytotoxic T cells that attack Copyright © 2009 Pearson Education, Inc. Immune Response Steps B cell Helper T cell Step 4: Alarm The helper T cell stimulates the B cell to begin dividing. B cell Step 5: Building specific defenses The B cell divides and forms plasma cells and memory cells. B cell Memory B cell Plasma cell Copyright © 2009 Pearson Education, Inc. Figure 13.12 (1 of 2) Immune Response Steps Step 5: Building specific defenses The B cell divides and forms plasma cells and memory cells. B cell Memory B cell Plasma cell Step 6: Defense Plasma cells secrete antibodies specific for that antigen. Plasma cell Antibodies Step 7: Continued surveillance Memory B cells remain and mount a quick response if the invader is encountered again. Memory B cells Copyright © 2009 Pearson Education, Inc. Figure 13.12 (2 of 2) Immune Response Steps 6. Primary defense Antibodies specific to the antigen eliminate the antigen Cytotoxic T cells release perforins that cause cells with the antigen to burst Copyright © 2009 Pearson Education, Inc. Immune Response Steps Immunoglobulins Five classes of antibodies, each with a special role to play in protecting against invaders IgG IgM IgE IgA IgD Copyright © 2009 Pearson Education, Inc. Immune Response Steps Copyright © 2009 Pearson Education, Inc. Figure 13.13 Immune Response Steps Copyright © 2009 Pearson Education, Inc. Table 13.4 Immune Response Steps 7. Immunological memory Allows for a more rapid response on subsequent exposure to the antigen Primary response may be slow as the antibody concentration rises Secondary response is strong and swift due to the large number of specific memory cells that can respond to the antigen Copyright © 2009 Pearson Education, Inc. Immune Response Steps Copyright © 2009 Pearson Education, Inc. Figure 13.15 Immune Response Steps 8. Suppressor T cells Turn off the immune response when the antigens no longer pose a threat Copyright © 2009 Pearson Education, Inc. Active Immunity Active immunity The body actively participates by producing memory B cells and T cells following exposure to an antigen This process can also happen through vaccination Because memory cells are produced, active immunity is relatively long lived Copyright © 2009 Pearson Education, Inc. Passive Immunity Passive immunity Results when a person receives antibodies that were produced by another person or animal Short lived since the recipient’s body was not stimulated to produce memory cells Copyright © 2009 Pearson Education, Inc. Monoclonal Antibodies Monoclonal antibodies A group of identical antibodies that bind to one specific antigen Used in research, clinical diagnosis, and disease treatment because they can help diagnose certain diseases in their early stages Copyright © 2009 Pearson Education, Inc. The Immune System Can Cause Problems Autoimmune disorders Failure to recognize distinguish between self and nonself Occur when the immune system attacks the body’s own cells Copyright © 2009 Pearson Education, Inc. The Immune System Can Cause Problems Copyright © 2009 Pearson Education, Inc. Figure 13.16 Immune System Problems Allergies Immune responses to harmless substances called allergens Allergens cause plasma cells to release large numbers of class IgE antibodies Copyright © 2009 Pearson Education, Inc. Immune System Problems Copyright © 2009 Pearson Education, Inc. Figure 13.17 Immune System Problems Copyright © 2009 Pearson Education, Inc. Table 13.6 Immune System Problems These IgE class antibodies bind to mast cells or basophils, causing them to release histamine The histamine causes redness, swelling, itching, and other symptoms of an allergic response Copyright © 2009 Pearson Education, Inc. Immune System Problems First exposure Step 1: The invader (allergen) enters the body. Allergen Step 2: Plasma cells produce large amounts of class IgE antibodies against the allergen. Plasma cell IgE antibody Step 3: IgE antibodies attach to mast cells, which are found in body tissues. Granules containing histamine Mast cell Copyright © 2009 Pearson Education, Inc. Figure 13.18 (1 of 2) Immune System Problems Subsequent (secondary) response Step 4: More of the same allergen invades the body. Step 5: The allergen combines with IgE attached to mast cells. Histamine and other chemicals are released from mast cell granules. Antigen Histamine Step 6: Histamine causes blood vessels to widen and become leaky. Fluid enters the tissue, causing swelling. • Histamine stimulates release of large amounts of mucus. • Histamine causes smooth muscle in walls of air tubules in lungs to contract. Copyright © 2009 Pearson Education, Inc. Figure 13.18 (2 of 2) Immune System Problems Antihistamines are most effective in reducing the allergy symptoms Copyright © 2009 Pearson Education, Inc. Immune System Problems Allergy shots inject increasing amounts of a known allergen in an effort to desensitize the person to the offending allergens Copyright © 2009 Pearson Education, Inc.