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Understanding the Immune System: Types, Functions, and Importance

Explore the different types of immunity, including innate and adaptive immunity, and learn about the functions and importance of the immune system. Discover how vaccines work and how HIV affects the immune system.

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Understanding the Immune System: Types, Functions, and Importance

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  1. Warm-Up (Review) • Compare bacteria vs. viruses. • When you think about your immune system, what are 5 words that come to your mind? • Think about this year’s flu epidemic. Why didn’t getting the flu shot last fall help many people who got sick with the flu?

  2. Chapter 35 Warm-Up Define the following terms: • Pathogen • Antigen • Antibody • Allergen • Vaccine

  3. Ch. 35 Warm-Up • What is the difference between innate vs. adaptive immunity? • Where are B and T cells produced and matured? • What is the role of antigen-presenting cells?

  4. Ch. 35 Warm-Up • Contrast the functions of B cells and T cells. • What are memory cells? • How do vaccines work? • How does HIV affect the immune system?

  5. THE IMMUNE SYSTEM Chapter 35

  6. Gross Science:Everything you didn’t want toknow about SNOT Running time: 4:25 min

  7. Types of Immunity

  8. Plant Defenses • Nonspecific responses • Receptors recognize pathogen molecules and trigger defense responses • Thicken cell wall, produce antimicrobial compounds, cell death • Localize effects

  9. Innate Immunity (Nonspecific)

  10. Barrier Defenses: • Skin • Secretions (pH 3-5 hostile condition) • Mucous membranes • Lysozyme (digestive enzyme in tears, saliva, mucus) • Antimicrobial Proteins: • Interferons (inhibit viral replication) • Complement system (~30 proteins, membrane attack complex  lysis) Innate Immunity (non-specific) • Natural Killer Cells: • Kill virus-infected and cancer cells • Inflammatory Response: • Macrophages release cytokines (signal molecules) • Mast cells release histamine • Blood vessels dilate, increase permeability (redness, swelling) • Deliver clotting agents, phagocytic cells • Fever • Phagocytic WBCs: • Neutrophils (engulf & destroy) • Macrophage (“big eaters”) • Dendritic cells (stimulate adaptive response) • Eosinophils (fight parasites)

  11. Inflammatory Response

  12. TLRs • Toll-like receptors (Toll: innate immunity activator in insects) • Binds to fragments of molecules from foreign pathogens • Increase efficiency of phagocytosis

  13. Phagocytosis • Engulf and destroy • Video: White blood cell chasing bacteria

  14. Bone marrow = blood cell & platelet production Main production areas = pelvis, femur, sternum (RBC) (platelets)

  15. The Immune System Explained Running time: 6:48 min

  16. Adaptive Immunity (Specific)

  17. Lymphatic System: involved in adaptive immunity

  18. 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

  19. Antigen: substance that elicits lymphocyte response

  20. Antibody(immunoglobulin – Ig): protein made by B cell that binds to antigens

  21. B and T Cell Diversity • Millions of differentB and T cells are produced by the immune system • Each unique cell has a specific antigen receptor

  22. How different antigen receptors are made

  23. Origin of Self-Tolerance • Undifferentiated B cell: • Ig (antibody) gene: DNA rearrangement + alternative splicing = different antigen receptors! • 1 million different B cell antigen receptors • 10 million different T cell antigen receptors • As lymphocytes mature in bone marrow or the thymus, they are tested for self-reactivity • B and T cells with “self” receptors programmed for cell death or nonfunctional

  24. Antigen-presenting cell Humoral Immune Response (antibodies) display antigen fragments Cell-Mediated Immune Response (T Cells) Helper T cell activates activates B cell Cytotoxic T cell divides releases cytokines Plasma cell Identify and destroy secretes tag for destruction Infected cell Antibodies pathogen

  25. Antigen-presenting cell Engulf pathogen, break up molecules and displays foreign molecules on surface

  26. Role of Helper T cells: “HELP!” (cytokines) activates B cells and cytotoxic T cells Clonal selection: produce thousands of cells specific to antigen (effector cells, memory cells)

  27. Clonal Selection (B cells) • Antigen binds to B cell receptor • Activation enhanced by cytokines • Millions of clones of B cells are made specifically for a specific antigen • Plasma cells: produce antibodies specific to that antigen • Memory cells: same receptor, but long-lived and can quickly mount immune response in future infections

  28. Clonal Selection (B cells)

  29. B cell  plasma cell  produce antibodies

  30. Antibodies mark pathogens for destruction Antibodiesbind to antigens and: Prevent viruses/toxins from entering cells Tag infected cells for destruction

  31. Cytotoxic T cells (Tc) kill infected cells disrupt membrane & trigger cell death

  32. Immunological Memory • Primary immune response: 1st exposure to antigen • Memory cells • Secondary immune response: repeat exposure  faster, greater response

  33. BioFlix: Immunology Running time: 6:51 min

  34. Major Histocompatibility Complex (MHC) • MHCs display proteins on cell surface • Responsible for tissue/organ rejection (“self” vs. “non-self”) • B and T cells bind to MHC molecule in adaptive response • MHC Class I: all body cells (except RBCs) • MHC Class II: displayed by immune cells; “non-self”

  35. Active vs. Passive Immunity Active immunity: exposure to antigen leaves behind memory cells Immunizations/vaccines: induce immune memory to nonpathogenic microbe or toxin Passive immunity: mom’s antibodies in breast milk passed to baby

  36. Immune System Disuptions • Allergies: hypersensitive responses to harmless antigens • Autoimmune Diseases: • Lose tolerance for “self” and turn against molecules in body; cytotoxic T cells attack and damage own cells • Lupus, rheumatoid arthritis, type I diabetes, multiple sclerosis • HIV: infect Helper T cells • AIDS = severely weakened immune system • Cancers: viruses involved in 20% of cancers; need to develop vaccines in fight cancer

  37. TED-Ed Video:Why it’s so hard to cure HIV/AIDS Running time: 4:31 min

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