Chapter 43 Warm-Up Define the following terms: Pathogen Antigen Antibody Allergen Vaccine What are lymphocytes? Where do B cells and T cells mature?
Ch. 43 Review Warm-Up What is the difference between innate vs. adaptive immunity? Contrast the functions of B cells and T cells. How are antigens recognized by immune system cells? What are memory cells? 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 Adaptive Immunity Non-specific All plants & animals 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
Pathogens (such as bacteria, fungi, and viruses) Figure 43.2 Pathogens (such as bacteria, fungi, and viruses) INNATE IMMUNITY (all animals) Barrier defenses: Skin Mucous membranes Secretions Recognition of traits shared by broad ranges of pathogens, using a small set of receptors • Internal defenses: Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response • Rapid response Figure 43.2 Overview of animal immunity. ADAPTIVE IMMUNITY (vertebrates only) Humoral response: Antibodies defend against infection in body fluids. Recognition of traits specific to particular pathogens, using a vast array of receptors • Cell-mediated response: Cytotoxic cells defend against infection in body cells. • Slower response
Innate Immunity Antimicrobial Proteins: Barrier Defenses: Interferons (inhibit viral reproduction) Complement system (~30 proteins, membrane attack complex) Barrier Defenses: 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: mature in thymus helper T, cytotoxic T B cells: stay and mature in bone marrow plasma cells antibodies
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: all body cells (except RBCs) Class II: displayed by immune cells; “non-self”
Cell-Mediated Immune Response Humoral Immune Response Antigen-presenting cell Cell-Mediated Immune Response (T Cells) Humoral Immune Response (antibodies) Helper T cell B cell Cytotoxic T cell Plasma cell tag for destruction Identify and destroy Infected cell Antibodies
Immunological Memory Primary immune response: 1st exposure to antigen Memory cells: Secondary immune response: repeat exposure faster, greater response
B cells that differ in antigen specificity Antigen Antigen receptor Figure 43.14 B cells that differ in antigen specificity Antigen Antigen receptor Figure 43.14 Clonal selection. Antibody Memory cells Plasma cells
Passive immunity: via antibodies in breast milk Immunizations/vaccines: induce immune memory to nonpathogenic microbe or toxin Passive immunity: via antibodies in breast milk Allergies: hypersensitive responses to harmless antigens Autoimmune Diseases: Lupus, rheumatoid arthritis, Type I diabetes, multiple sclerosis HIV: infect Helper T cells AIDS = severely weakened immune system