1. Chapter 43: The Body’s Defenses
How does your body protect you from invaders?

2. Immune System Review Microorganism/Microbe Pathogen Antibiotic
Antibody
Antigen

3. Key Concepts 3 Lines of Defense Innate vs. Acquired immunity
Phagocytes, Lymphocytes, Antibodies, etc…
Humoral vs. Cell-Mediated immunity
Distinguishing self from non-self
Tissue transplantation
Immune Diseases/Disorders

4. Using HIV to treat Cancer??

5. What do you think?
How does your body INITIALLY defend itself from invasion? (1st line – specific or non?)
What happens if the invader gets past the 1st line? (2nd line – specific or nonspecific?)
What about more serious infections? (3rd line)

6. 1st line Defense!!
Skin, mucus, cilia, saliva, acids, tears, oils, bacteria, coughing, sneezing, vomiting
Antimicrobial proteins & Lysozymes

7. Innate vs. Acquired Immunity
Innate Immunity:
Present before exposure; since birth
Includes natural bodily defenses, mother’s milk, or casual exposure
Broad-range capabilities, non-specific
External defenses:
skin, mucus membranes, tears
Internal Phagocytic cells
A.K.A.: “macrophages”; engulf invaders

8. Innate vs. Acquired Immunity
Develops only after exposure
Highly microbe-specific… how?
Employ lymphocytes & antibodies
Involves both Humoral & Cell-Mediated responses

9. Innate Immunity: Your first line of defense

10. Phagocytic White Blood Cells
Recognize & bind to carbohydrate markers on foreign cell membranes
Triggers receptor-mediated endocytosis
Engulf & digest pathogens via Phagocytosis

11. Types of White Blood Cells
Neutrophils: 60-70% of WBCs; engulf and destroy microbes at infected tissue; short lived
Monocytes: 5% of WBCs; develop into….
Macrophages: “big eaters” enzymatically destroy microbes; can be found in spleen, lymph nodes, and other organs
Eosinophils: 1.5% of WBCs; destroy large parasites extracellularly
Natural killer (NK) cells: trigger apoptosis in virus-infected cells & cancer cells

12. Leukocyte vs. Lymphocyte
White blood cells (WBC’s)
Lymphocyte =
Specific type of WBC that mature and migrate through the lymphatic system and target specific antigens via antibodies, receptors and toxin release

13. The Inflammatory Response
“Inflammation” = pain, swelling, fever, redness, itching, and pus

14. Causes of Inflammation
Injuries
Exposure to microbes/pathogens
Exposure to foreign objects or chemicals (insect bites, stings, medications, etc)
Exposure to allergens (pollen, pet dander, foods, etc)
Rare: sunlight, temperature, self!

15. The Inflammatory Response 3 Steps:
1. Tissue damage = release of chemical signals~
Mast cells release chemicals known as Histamine & Prostaglandins that trigger inflammation
2. Dilation increases permeability of capillaries~
Increased blood flow; leukocytes leak out to infected area
Delivery of clotting factors & antimicrobial proteins
3. Phagocytosis of pathogens~
WBC’s engulf microbes or damaged tissue
Fever: leukocyte-released chemicals increase body temperature

16. Acquired Immunity: Lymphocytes are the Key Defenders

17. Specific Immunity Antigen:
a foreign molecule that elicits a response from a lymphocyte
Lymphocyctes:
WBC’s that originate from stem cells in bone marrow
B Cells (mature in bone marrow)
T Cells (mature in thymus)
Antibodies:
antigen-binding immunoglobulin, produced by B cells
Antigen receptors:
membrane receptors on B and T cells

18. Ch. 43 Research: Humoral vs. Cell-mediated Responses
B cells vs. T cells
Memory cells
Clonal selection
Autoimmune disease

19. T cells vs. B cells B cells: T cells: Mature in Bone Marrow
Target in-tact Antigens
Part of Humoral Response
T cells:
Mature in Thymus
Target antigen fragments bound to MHC molecules on Infected Cells
Part of Cell Mediated Response

20. Humoral vs. Cell-Mediated
Humoral immunity
B cell activation
Production of antibodies
Defend against intact antigens free in the lymph and blood plasma
(bacteria, toxins, and viruses)

21. Humoral response: B cells
Stimulated by an antigen-presenting macrophage (WBC w/ a germ on it)
Activates Helper T cells
T cells secrete cytokine chemicals that activate B cells
B cells differentiate into memory B cells and antibody-producing plasma cells

22. Cytokines
Cytokine:
Proteins secreted by phagocytic cells (macrophages, etc.) and T-helper cells
Activate Lymphocytes (B & T cells)

23. Humoral Response: B cells activate. Plasma cells secrete antibodies.
Antibodies attach to antigens.
Antigens agglutinate (stick together) & get disposed.
Macrophages phagocytose or lyse the cell.

24. Cell-Mediated Cell-mediated immunity T cells are activated.
T cells bind to and/or lyse infected cells.
Defend against cells infected with bacteria, viruses, fungi, protozoa, parasites, even cancer!

25. Cell-mediated Response
1) Cell surface molecules expose antigens (foreign proteins).
2) Cytotoxic T cell releases perforin, a protein that forms pores in the target cell membrane.
causes cell lysis and exposes pathogens to circulating antibodies for disposal

26. Cell Mediated Response
Humoral Response
Antigens on Infected Cells
In Tact Antigens
B Cell Activation
T Cell Activation
Secrete antibodies that defend against pathogens & toxins in extracellular fluid
Defend against infected cells, cancer and transplanted tissues

27. Clonal Selection Clonal selection: Effector cells: Memory cells:
antigen-driven cloning of lymphocytes
Effector cells:
short-lived cells that combat the antigen initially
Memory cells:
long-lived cells that bear receptors for the antigen and activate upon subsequent exposure.

28. Active vs. Passive Immunity
Active: natural exposure to antigens causes one’s own lymphocytes to activate and produce antibodies
May also be acquired by Immunizations
Passive: direct transfer of antibodies through placenta or mother’s milk

29. HIV Human Immunodeficiency Virus
Causes AIDS (Acquired Immune Deficiency Virus)
HIV (a retrovirus) attacks helper T cells by binding with their cell receptor (CD4)
This impacts both the Humoral and Cell Mediated responses 

30. Clonal Selection Hypothesis
Each lymphocyte bears one specific type of receptor.
Receptor/antigen binding is required for cell activation.
Activated lymphocytes divide and give rise to cells with identical receptors to the parent.
This is how your immune system “remembers” a pathogen later!

31. Clonal Selection Hypothesis
First, those lymphocytes bearing receptors compatible to “self” tissues are destroyed (3)
Second, those bearing receptors that match foreign antigens are activated then cloned (5/6)

32. Self/Nonself Recognition
Self-tolerance:
Capacity to distinguish self from non-self molecules
Autoimmune diseases:
Failure of self-tolerance mechanisms
Multiple sclerosis, lupus, rheumatoid arthritis, insulin-dependent diabetes mellitus, Crohn’s disease

33. Abnormal immune function
Allergies:
hypersensitive responses to environmental antigens (allergens)
causes dilation and blood vessel permeability
Histamines are released from Mast cells
Autoimmune disease:
multiple sclerosis
Lupus
rheumatoid arthritis
insulin-dependent diabetes mellitus
Immunodeficiency disease:
SCIDS (bubble-boy)
A.I.D.S. (HIV)

34. Cancer & the Immune System
Tumor cells are targeted by both Cytotoxic T cells and Natural Killer (NK) cells
How might some tumors escape detection??

35. Treg research: Article Review
What are “Regulatory T Cells” (Tregs)?
What is their role in immunity?
How might they be linked with cancer?
Article: “Regulatory T cells and tumour immunity – observations in mice and men” by Gallimore and Godkin, 2007

36. Major Histocompatibility Complex
Aka: “MHC”
Cell surface proteins that display fragments of antigens or processed proteins on the cell surface
Epitope:
region of antigen surface
recognized by antibodies

37. Induction of Immune Responses
Primary immune response:
lymphocyte proliferation and differentiation the 1st time the body is exposed to an antigen
Plasma cells:
antibody-producing B-cells
Secondary immune response:
immune response if the individual is exposed to the same antigen at a later time~ Immunological memory

38. Types of Immunoglobins
IgM:
1st to circulate; indicates infection; too large to cross placenta
IgG:
most abundant; crosses walls of blood vessels and placenta; protects against bacteria, viruses, & toxins; activates complement
IgA:
produced by cells in mucous membranes; prevent attachment of viruses/bacteria to epithelial surfaces; also found in saliva, tears, and perspiration
IgE:
very large; small quantity; releases histamines-allergic reaction

39. Antibody-Mediated Antigen Disposal
Neutralization (opsonization):
antibody binds to and blocks antigen activity
Agglutination:
antigen clumping
Precipitation:
cross-linking of soluble antigens
Complement fixation:
lyses viruses and pathogenic cells & activates cell surface proteins to break down the cell

40. Immunity in Health & Disease
Active immunity:
natural: conferred immunity by recovering from disease
artificial: immunization and vaccination; produces a primary response
Passive immunity:
transfer of immunity from one individual to another
natural: mother to fetus; breast milk
artificial: rabies antibodies
ABO & Rh blood groups (antigen presence)