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Chapter 43 Warm-Up 1. Define the following terms: – – – – – Pathogen Antigen Antibody Allergen Vaccine 2. What are lymphocytes? Where do B cells and T cells mature? Ch. 43 Review Warm-Up 1. What is the difference between innate vs. adaptive immunity? 2. Contrast the functions of B cells and T cells. 3. How are antigens recognized by immune system cells? 4. What are memory cells? 5. How does HIV affect the immune system? Chapter 43 THE IMMUNE SYSTEM What you must know: • Several elements of an innate immune response • The differences between B and T cells relative to their activation and actions. • How antigens are recognized by immune system cells • The differences in humoral and cell-mediated immunity • Why Helper T cells are central to immune responses Types of Immunity Innate Immunity • Non-specific • All plants & animals Adaptive Immunity • Pathogen-specific • Only in vertebrates • Involves B and T cells Plant Defenses • Nonspecific responses • Receptors recognize pathogen molecules and trigger defense responses – Thicken cell wall, produce antimicrobial compounds, cell death • Localize effects Figure 43.2 Pathogens (such as bacteria, fungi, and viruses) INNATE IMMUNITY (all animals) • Recognition of traits shared by broad ranges of pathogens, using a small set of receptors • Rapid response ADAPTIVE IMMUNITY (vertebrates only) • Recognition of traits specific to particular pathogens, using a vast array of receptors • Slower response Barrier defenses: Skin Mucous membranes Secretions Internal defenses: Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response Humoral response: Antibodies defend against infection in body fluids. Cell-mediated response: Cytotoxic cells defend against infection in body cells. Antimicrobial Proteins: Barrier Defenses: •Interferons (inhibit viral reproduction) •Complement system (~30 proteins, membrane attack complex) •Skin •Mucous membranes •Lysozyme (tears, saliva, mucus) Innate Immunity (non-specific) Natural Killer Cells: •Virus-infected and cancer cells Inflammatory Response: •Mast cells release histamine •Blood vessels dilate, increase permeability (redness, swelling) •Deliver clotting agents, phagocytic cells •Fever Phagocytic WBCs: •Neutrophils (engulf) •Macrophage (“big eaters”) •Eosinophils (parasites) •Dendritic cells (adaptive response) Phagocytosis Inflammatory Response Lymphatic System: involved in adaptive immunity Adaptive Response Lymphocytes (WBCs): produced by stem cells in bone marrow •T cells: cells mature in thymus – helper T, cytotoxic T •B cells: cells stay and mature in bone marrow – plasma cells  antibodies • Antigen: Antigen substance that elicits lymphocyte response • Antibody (immunoglobulin – Ig): protein made by B cell that binds to antigens Major Histocompatibility Complex (MHC) • Proteins displayed on cell surface • Responsible for tissue/organ rejection (“self” vs. “non-self”) • B and T cells bind to MHC molecule in adaptive response • Class I: I all body cells (except RBCs) • Class II: II displayed by immune cells; “non-self” Antigenpresenting cell Cell-Mediated Immune Response (T Cells) Humoral Immune Response (antibodies) Helper T cell B cell Cytotoxic T cell Plasma cell tag for destruction Antibodies Infected cell Identify and destroy Immunological Memory • Primary immune response: 1st exposure to antigen • Memory cells: – Secondary immune response: repeat exposure  faster, greater response Figure 43.14 B cells that differ in antigen specificity Antigen Antigen receptor Antibody Memory cells Plasma cells • Immunizations/vaccines: Immunizations/vaccines induce immune memory to nonpathogenic microbe or toxin • Passive immunity: immunity via antibodies in breast milk • Allergies: Allergies hypersensitive responses to harmless antigens • Autoimmune Diseases: Diseases – Lupus, rheumatoid arthritis, Type I diabetes, multiple sclerosis • HIV: HIV infect Helper T cells – AIDS = severely weakened immune system