1. The Immune System
AP Biology Exam Review

2. Organization of the Immune System
Nonspecific Immunity
General defense against anything “not self” (MHC-I protein = “self”)
Primary cells: phagocytes (like macrophages) that “eat” invaders
Quicker
Specific Immunity
Targets specific invader
Primary cells: lymphocytes (T & B cells)
Slower, but builds “memory”

3. Organization of the Immune System
Skin Phagocytes Lymphocytes (B&T)
Mucous Membrane Fever Antibodies
Secretions Inflammation

4. Nonspecific Immunity Side note… Species Resistance
Why will you never catch Dutch elm rot?
Why will an apple tree never catch rabies?

5. Nonspecific Immunity
“1st line of defense” – physically &/or chemically block entry!
Mechanical Barriers
Skin & mucous membranes
physically block entry
This lines all outer surface as well as inner barriers
Note: your digestive tube is not “in” you (or respiratory, or…)

6. Nonspecific Immunity
“1st line of defense” – physically &/or chemically block entry!
Chemical Barriers
Oil & sweat on skin – creates low pH (non-native microbes can’t survive); anti-fungal compounds
Saliva & tears – contain lysozyme (breaks cell walls)
Mucus – sticky to trap them; also has lysozyme
HCl in stomach – few microbes can survive this

7. Nonspecific Immunity “2nd line of defense” Phagocytosis
Macrophages (& others) engulf invaders
While they are nonspecific…they can help to stimulate the specific mechanisms by sounding the alarm
Are APCs…antigen-presenting cells (antigen = invader particle)

8. Nonspecific Immunity “2nd line of defense” Chemical Mechanisms
Interferon
Protein released by virus-invaded cells
Chemical interferes with virus’ ability to attach to neighboring cells

9. Nonspecific Immunity “2nd line of defense” Chemical Mechanisms
Complement
Group of enzymes that lyse cells
Activated by specific or nonspecific

10. Nonspecific Immunity “2nd line of defense” Inflammation
Chemicals that stimulate inflammatory response: histamine, prostaglandins, leukotrienes
Increased blood flow & vessel permeability… helps WBCs get to infection site to phagocytize

11. Overview of Specific Immunity
Types of Specific Immunity
1. Inherited (Innate) – genetic; forms during gestation
- does not “last” as long
- includes species resistance
2. Acquired – after birth
Natural – form antibodies after exposure
Artificial – vaccines allow for antibody formation

12. Overview of Specific Immunity
Mechanisms
1. Humoral Immunity – has B cells with antibodies for indirect attack
2. Cell-mediated Immunity – has T cells with more direct attack
3. lymphocytes densest where they develop: bone marrow, thymus, lymph nodes, spleen

13. Specific Immunity
Humoral = fluid (blood) Cell-Mediated= cells

14. Specific Immunity Helper T-Cells (link btwn humoral & cell-mediated)
APCs (macrophages & some B’s) alert immune system to the foreign antigen by using helper T’s

15. Specific Immunity Helper T-Cells
Once activated, helper T’s secrete IL-2 (interleukin-2) that stimulates B cells to become plasma cells AND stimulates cytotoxic T cells to activate

17. Humoral Immunity (humor = fluid)
B-Cells develop in 2 stages
1. pre-B cells develop by few months of age (“inactive B cells”)
2. stage two (activation) in lymph nodes & spleen
Antigen binds to antibody receptor…they clone selves
Activated B = “plasma cells” (make antibodies)
Some remain as “memory B cells”

18. Humoral Immunity

19. Humoral Immunity Antibody Action
1. Plasma cells secrete specific counterparts to antigens, called antibodies
2. An antibody matches one specific antigen
Bind with it & bend it together…incapacitates it
3. this also stimulates inflammatory response & complement reactions
Antibodies fight against extracellular pathogens

20. Humoral Immunity

21. Humoral Immunity Antibody Structure & Function
1. Y-shaped; 4 polypeptide chains (how many genes?)
2. C-region (constant) is same in all antibodies
3. each chain topped with variable regions …allows for great diversity of antibodies
4. the epitope of the antigen binds at V-region
Antibodies fight against extracellular pathogens

22. Humoral Immunity Antibody Structure & Function
5. There are 5 major classes of antibodies (immunoglobulins) – do not memorize!
IgM – a pentamer; first to arrive on scene, so indicates current infection; cannot cross placenta (?)
IgG – most abundant
IgA – made by mucous membrane cells; milk
IgD – found on B cells; do not cross into placenta (?)
IgE – attach to mast cells & basophils; stimulate release of histamine in allergic reactions 
Do NOT need to memorize these

23. Cell-Mediated Immunity
A. T Cells Overview
1. these go thru thymus before nodes or spleen
2. Provide “direct attack”
3. Harder to activate – need 2 signals (why?)
Cytotoxic T-cells fight off intracellular pathogens

24. T Cell Activation & Function 1
T Cell Activation & Function 1. T cells must recognize “self” AND “nonself” at the same time to be activated
An APC uses the MHC-II to present antigen (depending on cell type, it might be an MHC-I, but same idea!)

25. Cell-Mediated Immunity
B. T Cell Activation & Function
2. It displays specific antigen receptor on own surface
3. an APC uses the MHC-II (or other) to present antigen …the T-cell binds with both
4. T cell divides, forming clones …called “sensitized T cells”
5. sensitized T cells will either be cytotoxic T cells or memory T cells

26. Cell-Mediated Immunity
B. T Cell Activation & Function
6. other types of T cells:
Suppressor T cells – suppress B cells from turning into plasma cells
Helper T cells – help B cells turn into plasma cells (discussed earlier)

27. Can you tell this story?

28. Side note… HIV Infection – attacks the T cells
Can you explain the data shown on the graph?

29. Review! Can you explain it?

30. Review! What does each do?

31. Review! Can you explain it?

32. Review! What’s going on here?

33. Review! What’s going on here?

34. The End

35. Free Response Practice
2014 #2 - Mammalian milk contains antibodies produced by the mother’s immune system & passed to offspring during feeding.
Describe FOUR steps in the activation of the mother’s immune response following exposure to a bacterial pathogen.
Predict how the mother’s immune response would differ upon a second exposure to the same bacteria a year later.
Predict the most likely consequence for a nursing infant who is exposed to an intestinal bacterial pathogen to which the mother was exposed three months earlier.

36. Free Response Practice
Explain how the human immune system…
A. provides an immediate nonspecific immune response
B. activates T and B cells in response to an infection.
C. responds to later exposure to same infectious agent
D. distinguishes self from nonself

37. Unit 7 Test: FreeResponse Rubric
A. – NONSPECIFIC
1 – physical barrier that blocks entry
skin, mucous membrane; saliva, tears, etc
2 – chemical barrier prevents entry/damages
Low pH/high salt kill, oil antifungal, lysozyme bursts
3 – inflammation – with description of any effect
4 – chemical agents – prevent spread or kill
Interferon, pyrogens, histamine (with description)
5 – phagocytosis – engulf invader
6 – elaboration (2nd ex. of #1/ #2; complement, etc)

38. Unit 7 Test: FreeResponse Rubric
39. (B) – ACTIVATING T & B CELLS
1 – macrophages engulf/present antigens
2 – TH or TC activated by binding to APC
3 – B cell activated by binding to antigen
4 – B or TC activated by binding to TH
5 – OTHER
TH secretes IL-2 to activate B or TC
CD4 on TH or CD8 on TC – self/nonself binding

39. Unit 7 Test: FreeResponse Rubric
39. (C) – SECONDARY EXPOSURE
1 – mediated by memory cells
2 – memory cells specific to SAME previous antigen
3 – antibody production is now faster/higher
4 – memory cell origin (activated cells  memory cells)
5 – memory cells more numerous OR antibody # high
6 – OTHER???

40. Unit 7 Test: FreeResponse Rubric
39. (D) – SELF from NON-SELF
1 – all cells have unique ID tags (self tags; MHC-I)
2 – developmental selection – how cells tested to ensure that attach nonself, but not attack self
3 – binding elicits the response (how it recognizes self/nonself)
4 – OTHER???
Describe self/nonself incompatabilities (bood transfusion; organ donation, etc)
Describe difference btwn MHC-I and MHC-II