Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Lymphopoiesis wikipedia , lookup
Immune system wikipedia , lookup
Psychoneuroimmunology wikipedia , lookup
Molecular mimicry wikipedia , lookup
Adaptive immune system wikipedia , lookup
Monoclonal antibody wikipedia , lookup
Innate immune system wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Cancer immunotherapy wikipedia , lookup
BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 24 The Immune System Modules 24.1 – 24.2 From PowerPoint® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Continuing Problem of HIV • Acquired immune deficiency syndrome (AIDS) is epidemic throughout much of the world • 14,000 people are infected with the AIDS virus every day – HIV is the virus that causes AIDS – HIV is transmitted mainly in blood and semen – Former L.A. Laker Magic Johnson is one of 900,000 Americans who are HIV-positive Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Our immune system is a specific defense system – It backs up several mechanisms of nonspecific resistance • HIV attacks the immune system – It eventually destroys the body’s ability to fight infection Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Basic Mechanisms of Defense • There are three basic lines of defense against disease • Vertebrate have all three lines of defense Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Basic Mechanisms of Defense • The 1st line of defense: nonspecific external barriers – Prevent microbes from entering the body – Examples: skin and mucous membranes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Basic Mechanisms of Defense • The 2nd line of defense: nonspecific internal barriers – Occurs when microbes breach nonspecific external barriers – Broad internal responses to microbe infection – Examples: phagocytic white blood cells, inflammation, fever Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Basic Mechanisms of Defense • The 3rd line of defense: specific immune response – Immune cells selectively destroy specific invading microbes and toxins – Invaders are “remembered,” allowing for a rapid future response to invasion Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings NONSPECIFIC DEFENSES AGAINST INFECTION 24.1 Nonspecific defenses against infection include the skin and mucous membranes, phagocytic cells, and antimicrobial proteins • The body’s first lines of defense against infection are nonspecific – They do not distinguish one infectious microbe from another Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Skin and Mucous Membranes • The skin is important in blocking microbe entry and suppressing microbe growth – Skin is a barrier to microbes – Skin is continually shed, removing microbes that gain a foothold on skin – Many skin secretions contain natural antibiotics Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Skin and Mucous Membranes • Mucous membranes have effective microbe defense mechanisms – Mucous membrane secretions contain antibacterial enzymes (example: lysozymes) – Mucus traps microbes entering the nose or mouth – Respiratory tract cilia sweep mucus and microbes away from lungs Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nonspecific Internal Defenses • Broad defenses that attack microbes that penetrate the skin • Three major categories of nonspecific internal defenses – Phagocytic cells and natural killer cells – The inflammatory response – Fever Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Macrophages wander in the interstitial fluid – They “eat” any bacteria and virus-infected cells they encounter Figure 24.1A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Natural Killer Cells • A type of white blood cell • Attack body cells that are cancerous or infected with virus – Secrete enzymes that poke holes in the cell membrane of virally-infected or cancerous cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fever • Helps combat large-scale infection by elevating body temperature Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fever • Some cells release cytokines in response to infection – Antibacterial cytokines • Macrophages release endogenous pyrogens: elevate body temperature • Other cytokines: decrease iron in the blood • Both act to slow bacterial reproduction – Antiviral cytokines: Interferon, which helps cells resist viral attack Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Interferon and complement proteins are activated by infected cells Viral nucleic acid VIRUS 6 Antiviral proteins block 1 viral reproduction 2 Interferon New viruses genes turned on mRNA 5 Interferon 3 stimulates cell to turn on genes for antiviral proteins Interferon molecules HOST CELL 1 Makes interferon; is killed by virus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 4 HOST CELL 2 Protected against virus by interferon from cell 1 Figure 24.1B 24.2 The inflammatory response mobilizes nonspecific defense forces • Tissue damage triggers the inflammatory response Skin surface Swelling Pin Phagocytes Bacteria Phagocytes and fluid move into area Chemical signals White blood cell 1 Tissue injury; release of chemical signals such as histamine 2 Dilation and increased leakiness 3 Phagocytes (macrophages and of local blood vessels; migration of phagocytes to the area neutrophils) consume bacteria and cell debris; tissue heals Figure 24.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The inflammatory response can – disinfect tissues – limit further infection Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.3 The lymphatic system becomes a crucial battleground during infection • The lymphatic system is a network of lymphatic vessels and organs – It returns tissue fluid to the circulatory system – It fights infections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings LYMPHATIC VESSEL Adenoid Tonsil Right lymphatic duct, entering vein Thoracic duct VALVE Lymph nodes Thoracic duct, entering vein Blood capillary Tissue cells Interstitial fluid Thymus Appendix Spleen LYMPHATIC CAPILLARY Masses of lymphocytes and macrophages Bone marrow Lymphatic vessels Figure 23.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • This lymphatic vessel is taking up fluid from tissue spaces in the skin • It will return it as lymph to the blood – Lymph contains less oxygen and fewer nutrients than interstitial fluid LYMPHATIC VESSEL VALVE Blood capillary Tissue cells Interstitial fluid LYMPHATIC CAPILLARY Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 23.3B • Lymph nodes are key sites for fighting infection – They are packed with lymphocytes and macrophages Masses of lymphocytes and macrophages Outer capsule of lymph node Macrophages Lymphocytes Figure 23.3C, D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings SPECIFIC IMMUNITY 24.4 The immune response counters specific invaders • Our immune systems responds to foreign molecules called antigens • Infection or vaccination triggers active immunity • The immune system reacts to antigens and “remembers” an invader • We can temporarily acquire passive immunity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Key Characteristics • The immune response involves specialized white blood cells called lymphocytes • The immune system: lymphocytes, the chemicals they produce, and the organs that they live in Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.5 Lymphocytes mount a dual defense • Two kinds of lymphocytes carry out the specific immune response BONE MARROW Stem cell THYMUS Via blood Immature lymphocytes – B cells secrete antibodies that attack antigens Antigen receptors HUMORAL IMMUNITY – T cells attack cells infected with pathogens Figure 24.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings T cell B cell OTHER PARTS OF THE LYMPHATIC SYSTEM Via blood CELLMEDIATED IMMUNITY Lymph nodes, spleen, and other lymphatic organs Final maturation of B and T cells in lymphatic organ An immune response has three steps – First: recognizing an invader – Second: launching an attack – Third: remembering specific invaders to ward off future infections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Step 1: Recognizing an Invader • Foreign invaders exhibit characteristic antigens – Foreign molecules that are particular to an invading microbe or toxin – Immune cells respond to the presence of antigens Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Antibodies and T-cell Receptors • Antibodies and T-cell receptors recognize and bind to foreign antigens Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Antibodies • Antibodies are proteins that can be attached to B cells or free-floating in the blood Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Antibodies • Antibodies – Y-shaped molecules made of light peptide chains and heavy peptide chains – Both chains have constant and variable regions that form highly specific antigen binding sites – Each type of antibody is unique to the B cell that makes them Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.10 Antibodies are the weapons of humoral immunity • An antibody molecule Figure 24.10A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Antibodies • There are five different classes of antibodies, which perform various functions – Inactivate their antigens by binding them and causing them to clump together – Assist white blood cells to engulf microbes – Activate natural killer cells – Bind to blood proteins of the complement system… Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Antibodies – Some classes of antibodies can cross the placenta and provide immunity to a developing child – Another class is secreted in breast milk – Both help the newborn, whose immune system is not fully developed Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.6 Antigens have specific regions where antibodies bind to them • Antigenic determinants (epitopes) are the molecules to which antibodies bind Antibody A molecules Antigenbinding sites Antigen Antigenic determinants Antibody B molecule Figure 24.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Immune Cells Launch an Attack • Once an invading antigen has been detected, two forms of attack occur –Humoral immunity –Cell-mediated immunity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.7 Clonal selection musters defensive forces against specific antigens • When an antigen enters the body, it activates only lymphocytes with complementary receptors – B and T cells multiply into clones of specialized effector cells that defend against the triggering antigen – This is called clonal selection Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Humoral Immunity • Provided by B cells and circulating antibodies • Attack antigens circulating in the bloodstream and lymph • Each B cell has a unique antibody attached to its surface that will only bind with properly shaped antigens Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Humoral Immunity • The mechanism of humoral immunity occurs in the following series of steps 1. Attached B cell antibodies bind to an invading antigen in the blood 2. Bound B cell divides rapidly forming many identical copies (clonal selection) 3. B cell clones differentiate to form memory B cells and plasma cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Antigen molecules Variety of B cells in a lymph node Antigen receptor (antibody on cell surface) Cell growth division, and differentiation Clone of many effector cells secreting antibodies Endoplasmic reticulum Antibody molecules Figure 24.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Humoral Immunity • Memory B cells: saved to fight future infection • Plasma cells: mass-produce the specific antibody into the blood Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.11 Antibodies mark antigens for elimination • Antibodies may – block harmful antigens on microbes – clump bacteria or viruses together – precipitate dissolved antigens – activate complement proteins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Binding of antibodies to antigens inactivates antigens by Neutralization (blocks viral binding sites; coats bacterial toxins) Agglutination of microbes Precipitation of dissolved antigens Complement molecule Bacteria Virus Antigen molecules Bacterium Enhances Phagocytosis Activation of complement Foreign cell Hole Leads to Cell lysis Macrophage Figure 24.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.8 The initial immune response results in a type of “memory” • In the primary immune response, clonal selection produces memory cells – These cells may confer lifelong immunity Figure 24.8A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • When memory cells are activated by subsequent exposure to an antigen, they mount a more rapid and massive secondary immune response Unstimulated lymphocyte First exposure to antigen FIRST CLONE Memory cells Second exposure to antigen Effector cells SECOND CLONE More memory cells New effector cells Figure 24.8B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.9 Overview: B cells are the main warriors of humoral immunity • Triggered by a specific antigen, a B cell differentiates into an effector cell – The effector cell is called a plasma cell – The plasma cell secretes antibodies Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PRIMARY RESPONSE (initial encounter with antigen) Antigen Antigen receptor on a B cell Antigen binding to a B cell Cell growth, division, and differentiation Clone of cells Memory B cell Plasma cell Antibody molecules SECONDARY RESPONSE (can be years later) Cell growth, division, and further differentiation Later exposure to same antigen Larger clone of cells Plasma cell Memory B cell Antibody molecules Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 24.9 24.12 Connection: Monoclonal antibodies are powerful tools in the lab and clinic • These molecules are produced by fusing B cells specific for a single antigenic determinant with easy-to-grow tumor cells Antigen injected into mouse B cells (from spleen) Tumor cells grown in culture Tumor cells Cells fused to generate hybrid cells Single hybrid cell grown in culture Antibody Figure 24.12A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hybrid cell culture, producing monoclonal antibodies • These cells are useful in medical diagnosis – Example: home pregnancy tests • They are also useful in the treatment of certain cancers Figure 24.12B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.13 T cells mount the cell-mediated defense and aid humoral immunity • Provided by T cells, which attack cancer cells and cells that have been invaded by viruses • Three types of T cells are involved – Helper T cells – Cytotoxic T cells – Memory T cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell-Mediated Immunity • Helper T cells – Bind to antigens “presented” by a macrophage that consumed them Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Cell-mediated immunity – An antigenpresenting cell (APC) first displays a foreign antigen and one of the body’s own self proteins to a helper T cell Microbe Macrophage (will become APC) 1 Antigen from microbe (nonself molecule) Self protein Self protein displaying antigen T cell receptor 3 2 Helper T cell Binding site for self protein 4 APC Binding site for antigen Figure 24.13A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell-Mediated Immunity • Helper T cells – Produce cytokines that stimulate T cell division and differentiation • Will form memory T cells and cytotoxic T cells • Will also stimulate division of B cells (humoral response) that are bound to an antigen Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The helper T cell’s receptors recognize the selfnonself complexes on the APC – The interaction activates the helper T cells – The helper T cell can then activate cytotoxic T cells with the same receptors Self protein displaying an antigen T cell receptor APC Interleukin-2 stimulates cell division Helper T cell Cytotoxic T cell Interleukin-2 activates other T cells and B cells B cell Interleukin-1 activates helper T cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell-mediated immunity (attack on infected cells) Humoral immunity (secretion of antibodies by plasma cells) Figure 24.13B • Cytotoxic T cells – Bind directly to cancerous or virally-infected cells – Release proteins that poke holes in cancer/infected cell membrane, killing the cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell-Mediated Immunity • Cytotoxic T cells bind to infected body cells and destroy them 1 Cytotoxic T cell binds to infected cell 2 Perforin makes holes in infected cell’s membrane Foreign antigen 3 Infected cell is destroyed Hole forming INFECTED CELL Perforin molecule Cytotoxic T cell Figure 24.13C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell-Mediated Immunity • Memory T cells – Dormant helper T cells that fight future infection by the antigen that produced it Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.14 Cytotoxic T cells may help prevent cancer • Cytotoxic T cells may attack cancer cells – The surface molecules of cancer cells are altered by the disease Figure 24.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.15 The immune system depends on our molecular fingerprints • The immune system normally reacts only against nonself substances – It generally rejects transplanted organs – The cells of transplanted organs lack the recipient’s unique “fingerprint” of self proteins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DISORDERS OF THE IMMUNE SYSTEM 24.16 Connection: Malfunction or failure of the immune system causes disease • Autoimmune diseases – The system turns against the body’s own molecules • Immunodeficiency diseases – Immune components are lacking, and infections recur • Physical and emotional stress may weaken the immune system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.17 Connection: Allergies are overreactions to certain environmental antigens • Allergies are abnormal sensitivities to allergens in the surroundings B cell (plasma cell) Histamine Antigenic determinant Allergen (pollen grain) Mast cell B cells make antibodies Antibodies attach to mast cell SENSITIZATION: Initial exposure to allergen Allergen binds to antibodies on mast cell Histamine is released, causing allergy symptoms LATER EXPOSURE TO SAME ALLERGEN Figure 24.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.18 Connection: AIDS leaves the body defenseless • The AIDS virus attacks helper T Cells – This cripples both cell-mediated and humoral immunity • So far, AIDS is incurable – Drugs and vaccines offer hope for the future • Practicing safer sex could save many lives Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings