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  • 1. Chapter 43: The Immune System By Phenix Messersmith Evan Schwartz Brian Shea Mike Gaunt
  • 2. Innate Immunity: Nonspecific Defense Mechanisms
    • External - first line of defense: called barrier defense (ex. skin, mucous membranes, and secretions of skin and mucous membranes)
    • Internal – second line of defense: phagocytic white blood cells, antimicrobial proteins, the inflammatory response
  • 3. The Inflammatory Response
    • Four main steps:
    • #1- chemical signals cause capillaries to widen
    • #2- fluid, other clotting elements move to site of injury; clotting begins
    • #3- Chemokines released by various cells attract more phagocytic cells to injury cite
    • #4- Neutrophils and macrophages engulf pathogens and cell debris. Tissue heals.
  • 4. Leukocytes
    • Phagocytic white blood cells: neutrophils, macrophages, eosinophils, and dendritic cells
    • Engulfs infected bacteria and infected tissue
    • Discharges destructive enzymes
  • 5. Acquired Immunity: Specific Defense
    • Third line of defense
    • Examples: lymphocytes (white blood cells) and antibodies (proteins secreted by B cells)
    • Able to distinguish one inducing agent from another
    • Fight against antigens (foreign molecule that elicits a specific response by a lymphocyte)
  • 6. Different Types of Lymphocytes
    • B Lymphocytes (B cells) –
    • develop in bone marrow;
    • after encountering antigens
    • they change to
    • antibody-secreting plasma
    • cells (the effector cells of humoral immunity)
    • T Lymphocytes (T cells) – develop in the thymus; after encountering antigens they are responsible for cell mediated immunity
  • 7. More On B Cells
    • Antigens bind to specific receptors and cytokines secreted from helper T cells then activate B cells
    • Once activated they generate antibody-secreting effector cells or plasma cells
  • 8. MHC: Major Histocompatibility Complex
    • Responsible for stimulating the immune response of T cells by binding to antigens so that T cell receptors can recognize them
    • Process called antigen presentation
  • 9. Different Types of T Cells
    • Cytotoxic T Cells- kill infected cells, cancer cells, and transplanted cells after being activated by recognizing Class I MHC molecules
    • Helper T Cells- secrete cytokines that promote response of B cells and cytotoxic T cells to antigens when activated by recognizing Class II MHC molecules
  • 10. The Lymphatic System
    • A system of vessels and lymph nodes separate from the circulatory system that returns fluid and protein to the blood
    • Stores and reproduces macrophages and other such white blood cells who fight off infections
  • 11. Antibodies
    • Aid in immunity by:
    • 1- viral neutralization (blocks binding to host)
    • 2- opsonization (increases phagocytosis)
    • 3- agglutination (forms aggregates that can be readily phagocytosed by macrophages)
    • 4- precipitation (of soluble antigens dissolved in body fluids)
  • 12. Primary Response vs. Secondary Response
    • Initial acquired immune response to an antigen which peaks about 10 to 17 upon first exposure
    • When the same antigen enters the body and the response is faster, about 2 to 7 days, because there are more antibodies in the blood
  • 13. Active vs. Passive Immunity
    • Active: long-lasting, conferred by action of B and T cells and resulting B and T memory cells specific for pathogen
    • Passive: Short-term, conferred by administration of ready made antibodies or the transfer of maternal antibodies to fetus or nursing infant
  • 14. Allergies
    • Hypersensitive responses to certain environmental antigens, called allergens
    • Scientists believe allergies are evolutionary remnants of immune system’s response to parasitic worms
  • 15. HIV: Human Immunodeficiency Virus
    • Retrovirus that gains entry into the cells by using different cell types, such macrophages and brain cells, that have low levels of CD4 as receptors and co-receptors
    • Main receptor for HIV is the CD4 molecule on helper T cells, this infection and loss of helper T cells allows the rise of AIDS