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