32-1 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease Infection The presence of a pathogen in or on the body Pathogen A disease-causing agent Innate immunity Nonspecific defenses to protect against pathogens Nonspecific defenses Species resistance Mechanical barriers Chemical barriers Phagocytosis Fever Inflammation

32-2 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease: Specific Defenses Immunities Protect against very specific pathogens Antigens Foreign substances in the body Haptens Foreign substances too small to start an immune response by themselves Other substances Proteins – antibodies and complements WBCs – lymphocytes and macrophages Lymph system Cytokines – assist in immune response regulation Monokines – increase B cell production and stimulate WBC production

32-3 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease (cont.) Two major types of lymphocytes B Cells and T Cells Recognize antigens in the body T Cells  Cell-mediated response  Bind to antigens on cells and attack them directly  Secrete lymphokines that increase T cell production and directly kill cells with antigens T Cells  Cell-mediated response  Bind to antigens on cells and attack them directly  Secrete lymphokines that increase T cell production and directly kill cells with antigens B cells  Respond to antigens by becoming plasma cells  Plasma cells make antibodies  Memory B cells produce stronger response with next exposure to antigen B cells  Respond to antigens by becoming plasma cells  Plasma cells make antibodies  Memory B cells produce stronger response with next exposure to antigen Response

32-4 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease (cont.) T cell activation Begins when macrophage ingests and digests pathogen with antigen on it Antigens are placed on cell membrane of macrophage T cell recognizes and binds to antigen and the major histocompatibility complex (MHC) on the surface of the macrophage Now can divide to form other types of T cells

32-5 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease (cont.) Types Cytotoxic T cells Protect body against viruses and cancer cells Helper T cells Increase antibody formation, memory cell formation, B cell formation, and phagocytosis Memory T cells Remember the pathogen that activated original T cell Later exposures trigger an immune response more effective than initial response

32-6 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Defenses Against Disease (cont.) Natural killer (NK) cells Type of lymphocyte Primarily target cancer cells Kill on contact Do not recognize a specific antigen

32-7 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Antibodies Also called immunoglobulins IgA Prevents pathogens from entering body IgD Found on B cell membranes Thought to control B cell activity IgE Found with IgA Involved in triggering allergic reactions

32-8 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Antibodies (cont.) IgG Recognizes bacteria, viruses, and toxins Activates complements IgM Large and binds to antigens on food, bacteria, or incompatible blood cells Activates compliments

32-9 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Antibodies (cont.) Actions that occur when antibodies bind to antigens Allow phagocytes to recognize and destroy antigens Cause antigens to clump together, causing them to be destroyed by macrophages Cover the toxic portions of antigens, making them harmless Activate complement Group of proteins in serum that attack pathogens by forming holes in them Attract macrophages to pathogens and can stimulate inflammation

32-10 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Immune Responses and Acquired Immunity Primary immune response occurs with first exposure to antigen Slow process Memory cells are formed Secondary immune response with next exposure to same antigen Quick and carried out by memory cells Usually prevents person from developing disease from the antigen

32-11 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Immune Responses and Acquired Immunity (cont.) Naturally acquired active immunity Natural exposure to antigen – having an illness Makes antibodies and memory cells Long-lasting Artificially acquired active immunity Injected with pathogen – immunizations Makes antibodies and memory cells Long-lasting

32-12 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Immune Responses and Acquired Immunity (cont.) Naturally acquired passive immunity Acquired from mother Breast milk Placenta Short-lived Artificially acquired passive immunity Injected with antibodies (such as antivenom) Short-lived

32-13 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Major Immune System Disorders Cancer Uncontrolled growth of abnormal cells form malignant tumors 200 known types Treatment based on stage 0 – very early; cancer cells localized I – spread to deeper layers or some in surrounding tissues II – spread to surrounding tissues but contained in primary site III – spread beyond primary site into nearby areas IV – spread to other organs Recurrent – reappeared after treatment

32-14 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Major Immune System Disorders (cont.) Allergies Immune response to an allergen Can be excessive IgE antibodies bind to allergens and stimulate mast cells to release histamine and heparin Triggers allergic response Allergy shots Small amounts of allergen stimulates production of IgG to prevent IgE from binding to antigen IgG antibodies do not stimulate mast cells, so immune response is not generated

32-15 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Signs/symptoms Inhaled allergens – runny nose, sneezing, coughing, wheezing Ingested allergens – nausea, vomiting, diarrhea Skin allergens – rashes Allergens in blood – most life-threatening; can affect many organs Treatment Antihistamines, decongestants – OTC or prescription Epinephrine for anaphylaxis – vasoconstriction, increasing BP Anaphylaxis – life-threatening response Major Immune System Disorders (cont.)

32-16 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Common Immune System Disorders Autoimmune disease Body attacks its own antigens Examples Scleroderma Rheumatoid arthritis Multiple sclerosis Glomerulonephritis Chron’s disease Diabetes mellitus, type I

32-17 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Common Immune System Disorders (cont.) DisorderDescription AIDSDevelopment of severe signs and symptoms caused by HIV as it destroys lymphocytes; leaves immune system weakened and susceptible to other diseases Chronic fatigue syndrome (CFS) Condition of severe tiredness not relieved by rest and not related to other illnesses LymphedemaBlockage of lymphatic vessels results in tissue swelling that increases over time

32-18 © 2009 The McGraw-Hill Companies, Inc. All rights reserved Common IS Disorders (cont.) DisorderDescription Mononucleosis“Mono”; highly contagious viral infection spread through saliva of infected person Systemic lupus erythematous (SLE) Autoimmune disorder; antibodies produces that target own cells and tissues; affects women more often than men

32-19 © 2009 The McGraw-Hill Companies, Inc. All rights reserved In Summary Immune system is the body’s major line of defense Primary function – protect against infection, toxins, and cancer Specific or nonspecific defenses Lymphocytes are major cells of immune system Immune response may be primary or secondary Medical assistant must understand immune system Aseptic technique Infection control Educate patients