1. Chapter 43 Warm-Up Define the following terms:
Pathogen
Antigen
Antibody
Allergen
Vaccine
What are lymphocytes? Where do B cells and T cells mature?

2. 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?

3. Chapter 43
THE IMMUNE SYSTEM

4. Introduction to the Immune System
Independently Close Read the text and then complete the “questions” with a partner

5. 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

6. Types of Immunity Adaptive Immunity Innate Immunity (Acquired)
Non-specific
All plants & animals
Pathogen-specific
Only in vertebrates
Involves B and T cells

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

8. 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

9. 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)

10. Phagocytosis
Video: Macrophages

11. Inflammatory Response

12. Lymphatic System: involved in adaptive immunity

13. 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

14. Antigen: substance that elicits lymphocyte response
Antibody (immunoglobulin – Ig): protein made by B cell that binds to antigens

15. 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”

16. Origin of Self-Tolerance
Read the text closely to yourself.
Talk to a neighbor to summarize what you think are the key points.
Re-write / Summarize these points in the box.
You may use bullets.
What questions do you still have?
Antigen receptors are generated by random rearrangement of DNA
As lymphocytes mature in bone marrow or the thymus, they are tested for self-reactivity
Some B and T cells with receptors specific for the body’s own molecules are destroyed by apoptosis, or programmed cell death
The remainder are rendered nonfunctional
© 2011 Pearson Education, Inc.

17. Video:
Specific Immunity B Cells and T Cells. Humoral and cell mediated response. Dr. Dawes video Tutor.

18. Reading with a Purpose
Pay attention to the vocabulary and the “story” of how the adaptive immune system works.
Answer the questions that follow.

19. 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
Video

20. Analyze the diagram. Discuss it with a neighbor
Analyze the diagram. Discuss it with a neighbor. Write responses to the 3 questions in your notes.

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

22. B cells that differ in antigen specificity Antigen Antigen receptor
Figure 43.14
B cells that differ in antigen specificity
Antigen
Antigen receptor
Figure Clonal selection.
Antibody
Memory cells
Plasma cells

25. Cell- mediated immunity
Figure 43.16
Antigen- presenting cell
Antigen fragment
Pathogen
Class II MHC molecule 1
Accessory protein
Antigen receptor
Helper T cell 
Cytokines 
Figure The central role of helper T cells in humoral and cell-mediated immune responses. 2
Cell- mediated immunity
Humoral immunity   3
B cell
Cytotoxic T cell

26. B Cells and Antibodies: A Response to Extracellular Pathogens
The humoral response is characterized by secretion of antibodies by B cells
Activation of the humoral immune response involves B cells and helper T cells as well as proteins on the surface of pathogens
In response to cytokines from helper T cells and an antigen, a B cell proliferates and differentiates into memory B cells and antibody secreting effector cells called plasma cells
© 2011 Pearson Education, Inc.

27.  1 2 3 Antigen-presenting cell Pathogen Antigen fragment B cell
Figure
Antigen-presenting cell
Pathogen
Antigen fragment
B cell
Class II MHC molecule
Memory B cells 
Accessory protein
Cytokines
Antigen receptor
Figure Activation of a B cell in the humoral immune response.
Activated helper T cell
Helper T cell
Plasma cells
Secreted antibodies 1 2 3

28. Antibody Function
Antibodies do not kill pathogens; instead they mark pathogens for destruction
A. In neutralization, antibodies bind to viral surface proteins preventing infection of a host cell
B. Antibodies may also bind to toxins in body fluids and prevent them from entering body cells
© 2011 Pearson Education, Inc.

29. C. In opsonization, antibodies bind to antigens on bacteria creating a target for macrophages or neutrophils, triggering phagocytosis
D. Antigen-antibody complexes may bind to a complement protein —which triggers a cascade of complement protein activation
E. Ultimately a membrane attack complex forms a pore in the membrane of the foreign cell, leading to its lysis
© 2011 Pearson Education, Inc.

30. Activation of complement system and pore formation Neutralization
Figure 43.19
Activation of complement system and pore formation
Neutralization
Opsonization
Complement proteins
Antibody
Formation of membrane attack complex
Bacterium
Virus
Flow of water and ions
Pore
Figure Antibody-mediated mechanisms of antigen disposal.
Foreign cell
Antigen
Macrophage

31. Antibody Structure

32. IgM: First soluble class produced
B cells can express five different forms (or classes) of immunoglobulin (Ig) with similar antigen-binding specificity but different heavy chain C regions
IgD: Membrane bound
IgM: First soluble class produced
IgG: only one that can cross the placenta (involved in passive immunity); most abundant
IgA: found in mucous (secretory)
IgE: involved in allergic reactions
© 2011 Pearson Education, Inc.

33. Histamine IgE Allergen Granule Mast cell Figure 43.22
Figure Mast cells, IgE, and the allergic response.
Granule
Mast cell

34. The next time the allergen enters the body, it binds to mast cell–associated IgE molecules
Mast cells release histamine and other mediators that cause vascular changes leading to typical allergy symptoms
An acute allergic response can lead to anaphylactic shock, a life-threatening reaction, within seconds of allergen exposure
© 2011 Pearson Education, Inc.

35. Bozeman Science
The Immune System

36. 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

37. Immune Rejection
Cells transferred from one person to another can be attacked by immune defenses
This complicates blood transfusions or the transplant of tissues or organs
© 2011 Pearson Education, Inc.

38. Blood Groups
Antigens on red blood cells determine whether a person has blood type A (A antigen), B (B antigen), AB (both A and B antigens), or O (neither antigen)
Antibodies to nonself blood types exist in the body
Transfusion with incompatible blood leads to destruction of the transfused cells
Recipient-donor combinations can be fatal or safe
© 2011 Pearson Education, Inc.

39. Tissue and Organ Transplants
MHC molecules are different among genetically nonidentical individuals
Differences in MHC molecules stimulate rejection of tissue grafts and organ transplants
Chances of successful transplantation increase if donor and recipient MHC tissue types are well matched
Immunosuppressive drugs facilitate transplantation
Lymphocytes in bone marrow transplants may cause the donor tissue to reject the recipient
© 2011 Pearson Education, Inc.

40. Autoimmune Diseases
In individuals with autoimmune diseases, the immune system loses tolerance for self and turns against certain molecules of the body
Autoimmune diseases include systemic lupus erythematosus, rheumatoid arthritis, insulin-dependent diabetes mellitus, and multiple sclerosis
© 2011 Pearson Education, Inc.

41. Exertion, Stress, and the Immune System
Moderate exercise improves immune system function
Psychological stress has been shown to disrupt immune system regulation by altering the interactions of the hormonal, nervous, and immune systems
Sufficient rest is also important for immunity
© 2011 Pearson Education, Inc.

42. Immunodeficiency Diseases
Inborn immunodeficiency results from hereditary or developmental defects that prevent proper functioning of innate, humoral, and/or cell-mediated defenses
Acquired immunodeficiency develops later in life and results from exposure to chemical and biological agents
Acquired immunodeficiency syndrome (AIDS) is caused by a virus
© 2011 Pearson Education, Inc.

43. Latency
Some viruses may remain in a host in an inactive state called latency
Herpes simplex viruses can be present in a human host without causing symptoms
© 2011 Pearson Education, Inc.

44. Attack on the Immune System: HIV
Human immunodeficiency virus (HIV) infects helper T cells
The loss of helper T cells impairs both the humoral and cell-mediated immune responses and leads to AIDS
HIV eludes the immune system because of antigenic variation and an ability to remain latent while integrated into host DNA
© 2011 Pearson Education, Inc.

45. Helper T cell concentration (in blood (cells/mm3)
Figure 43.25
Latency
AIDS
Relative anti-HIV antibody concentration
800
Relative HIV concentration
600
Helper T cell concentration (in blood (cells/mm3)
Helper T cell concentration
400
Figure The progress of an untreated HIV infection.
200 1 2 3 4 5 6 7 8 9 10
Years after untreated infection

46. The spread of HIV is a worldwide problem
People with AIDS are highly susceptible to opportunistic infections and cancers that take advantage of an immune system in collapse
The spread of HIV is a worldwide problem
The best approach for slowing this spread is education about practices that transmit the virus
© 2011 Pearson Education, Inc.

47. Cancer and Immunity
The frequency of certain cancers increases when adaptive immunity is impaired
20% of all human cancers involve viruses
The immune system can act as a defense against viruses that cause cancer and cancer cells that harbor viruses
In 2006, a vaccine was released that acts against human papillomavirus (HPV), a virus associated with cervical cancer
© 2011 Pearson Education, Inc.