Immune System

LECTURE OUTLINE (CHAPTER 24)

LECTURE OBJECTIVES

1. List the general functions of the immune system and how each works.
2. Describe the innate immune responses to a foreign agent, such as inflammation, invasion by leukocytes, interferon, membrane attach complexes, natural killer cells, and complement.
3. Explain acquired immunity to a foreign agent, such as antibody-mediated immunity and cell-mediated immunity.
4. What is the structure of antibodies?
5. Explain how antibodies hinder foreign agents by neutralization, agglutination, phagocytotic enhancement etc..
6. Explain how clonal selection theory results in the proliferation of specific antibodies.
7. Establish how Helper T cells augment the immune response.
8. Describe the role of Major Histocompatability Complexs and self-antigens in the immune response.
9. Consider some of the medical implications of immunity (allergies, autoimmune diseases, transplant rejection, etc.)

LECTURE OUTLINE

I.  INTRODUCTION TO THE IMMUNE SYSTEM

  A.  General Functions of the Immune System
     1. Pathogen defense 
     2. Removal of worn out and dead cells
     3. Destruction of aberrant cells in the body 
     4. Phagocytosis of cellular debris and foreign cells
  B.  Leukocytes and what they do
     1. There are a number of different leukocytes
          a. Neutrophils
          b. Eosinophils
          c. Basophils
          d. Monocytes
          e. Lymphocytes (B and T cells)
           f. Dendritic cells
     2. Leukocytes are mobile and squeeze through capillaries
  C. Lymphoid tissues and immunity
     1. Organization of the immune system
          a. Located to intercept foreign substances
     2. Lymph node structure and function
  D. Innate and acquired immunity
     1. Comparison of these immune responses

II. INNATE IMMUNITY 
 
  A. Inflammation
     1.  Wall it off -> Destroy foreign agent -> Heal/repair tissue
     2.  Specifics of the inflammation response
  B. Natural Killer (NK) Cells and Interferon
     1. NK Cells kills infected cells
     2. Interferon interrupts viral protein synthesis
  C. Complement System
     1. Complement is activated through a cascade of events
     2. Membrane Attack Complexes (MAC) insert in bacterial 
         membrane

III. ACQUIRED IMMUNITY 

  A. Characteristics of Acquired Immunity
  B. Antibody Immunity (B lymphocytes)
     1. Antibodies are highly specific proteins
     2. Antibody structure is conserved except for the Fab
          a.  Y-shaped
          b.  AB-Antigen is a "lock and key" relationship
     3. Antibody actions
          a. Neutralization of toxins, agglutination, activate non-
              specific responses (NK cells, phagocytosis, complement)
          b. Anitbodies assist innate immunity but don't kill invaders 
     4. An antigen stimulates a specific clone of B lymphocytes
          a. Clonal Selection Theory
               1) Functions of plasma cells and memory cells
          b. Primary and Secondary immune responses
               1) Vaccination--a good thing.
               2) Allergies--a bad thing.
          c. Natural immunity 
               1) ABO blood types 
               2) Transfusion reaction
               3) Rhesus disease in the fetus
          d. Rejection of organ transplants
  C. T Lymphocytes: Cell-mediated immunity
     1. Cytotoxic T cells
          a.  Lyse the cell directly or via Perforin
     2. Roles of the Helper T cells
          a. Act through interleukins/cytokines
          b. AIDS--HIV infection targets Helper T cells 
  D. Major Histocompatability Complexes (MHC)
     1. MHCs are unique to each individual
     2. Cytotoxic T and Helper T cells distinguish self-antigens and foreign 
         antigens to identify an infected cell
         a. Cytoxic T cells kill the infected cell via perforin, etc. 
  E. Autoimmunity
     1. Causes of autoimmunity
          a. Reduction in Supressor T cells
          b. Modified self-antigens, etc.
     2.  Autoimmune diseases (MS, Myasthenia gravis, Arthritis, Lupus)

Reading Assignment. For the next lecture, please read Chapter 17 and the beginning of Chapter 18.



STUDY QUESTIONS ON THE IMMUNE SYSTEM (CHAPTER 24)

    BASIC FACTS AND TERMS

  1. List the multiple functions of the immune system. Which tissues/organs are involved in the immune response and how does each function?

  2. Define innate and acquired immunity. What are the general characteristics of each? What are the advantages of having multiple defenses (Innate and acquired) against the same antigen?

  3. List four innate immune responses present in the body. How does each function to combat infection?

  4. How do leucocytes pass from the blood stream into an area of infection? What chemical factors guide their migration? How is positive feedback involved in recruiting neutrophils to an area of infection? Review phagocytosis (See Figure 5-23 in Silverthorn).

  5. By what mechanism do glucocorticoids (=steroid hormones from the adrenal cortex) suppress inflammation?

  6. List the general types of white blood cells (Figure 24-4 in Silverthorn). What is the function of each type?

  7. Compare active and passive immunity (see Silverthorn). Explain the role of passive immunity during fetal development and immediately following birth?

  8. What are lymph nodes and how do they function in the immune system? How does the structural organization of the lymph node reflect its function? What type of leucocyte resides in the lymph nodes? What are some other organs that house leucocytes?

  9. What are the general functions of B and T cells? What are the subpopulations of T cells? What is the specific function of each T cell type in the immune response? Compare and contrast the properties of the B and T cells.

  10. Define and given the physiological significance (how or why it is important) for the following terms:
    • Thymus
    • Histamine
    • Kinens
    • Prostaglandins
    • Pyrogens
    • Complement system
    • Natural immunity
    • Membrane Attack Complex (MAC)
    • Antibody
    • Cytokines
    • Interferon
    • Perforin
    • Transfusion reaction
    • Clonal Selection Theory
    • Major Histocompatibility Complex I and II (MHC)
    • Memory cells (of the immune system)
    • Rhesus disease

  11. What are the immunoglobulins (Ig) and in general how does each function?


    CONCEPTS

  12. Outline the inflammation response. What local factors initiate this response? Explain the biological basis for why a wound area is slightly redder, warmer, and more swollen than surrounding areas. How do local secretions from phagocytic cells affect the inflammation response? Review Fig. 24-17 for specifics.

  13. The inflammation response is a complex of positive feedback loops. What is the general purpose of these loops?

  14. What is autoimmunity? List some of the diseases resulting from an autoimmune response. What processes make the immune system normally tolerant of self-antigens? (See Table 24-4)

  15. Compare a primary immune response and a secondary immune response (e.g. in timing, in amplitude). What is a vaccination and how does it relate to primary and secondary immune responses?

  16. How are the ABO blood types related to the immune system? What is Rh factor (+ or -)? When a person with an A- blood type is given type B+ blood, the infused blood agglutinates. Explain the immune basis for this transfusion reaction. Here is another one. A person with type A blood is transfused with type O. What happens and why? See pages 798-799.

  17. What structural characteristics do all antibodies have in common? How does the antibody recognize a specific antigen? Explain how it is possible that B lymphocytes as a group can produce so many different, but highly specific, antibodies.

  18. How do antibodies help eliminate invading microbes and the toxins that they might produce? What other functions do they have? (See Figure 24-13)

  19. Rejection of an transplanted organ is an immune response. Explain the cellular basis for organ rejection. Briefly discuss ways that are used to minimize organ rejection.

  20. Read about the HIV virus in the "Running Problem" of Chapter 24.How does this virus affect the immune system?

  21. How does the immune system respond to a bacterial infection (See Fig. 24-17)? How do these mechanisms contrast with those following a viral infection (See Fig. 24-18)?


    REASONING AND PROBLEM SOLVING

  22. The white blood cell count is an important diagnostic tool. If the count shows an increase in the number of neutrophils in circulation, is it more likely to be a bacterial or viral infection? Briefly explain. If the count shows an increase in the number of eosinophils, is it more likely to be a viral or a parasitic infection? Briefly explain.

  23. A laboratory rat is given a drug that blocks cellular phagocytosis. Will this drug prevent the animal's immune system from killing foreign cells by means of the complement system? Defend your answer.

  24. What abnormalities would a person with a neutrophil deficiency display? A person with a monocyte (=macrophage) deficiency?

  25. How does the immune system defend against viral attack? Although it might seem that we should acquire immunity to viral flu infections, we continue to be susceptible year after year. Why isn't the immune system that effective at combating the flu?

  26. What are the physiological events that generate an allergic response (See Fig. 24-9)? How do antihistamines help reduce an allergic attack? Why is anaphylactic shock so dangerous, and why is epinephrine often given as a treatment for this type of shock?

Last revised: March 6, 2008