1. Chapter 15 Innate and Adaptive Immunity

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4. Innate Immunity Always present Attacks non-self microbes
Does not distinguish between different microbes
Mechanisms include:
Epithelial barriers
Phagocytic cells
Plasma proteins
Cell messenger molecules

5. Adaptive Immunity Attacks specific microbes (antigens)
Develops after exposure to the specific antigen
Mechanisms include:
Humoral immunity (antibody proteins in the blood that attack the specific antigen)
Cell-mediated immunity (phagocytic cells that attack the specific antigen)

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7. Question Tell whether the following statement is true or false:
A vaccination is an example of adaptive immunity.

8. Answer
True
In adaptive/acquired immunity, specific antigens are attacked, and immunity develops after exposure to the specific antigen. When you get a vaccine, you are getting a live, weakened, or dead microbe (a specific antigen). Your body develops antibodies to attack that antigen after you are exposed.

9. Immune Cells Regulatory cells control the immune response
T helper cells
T suppressor cells
Antigen presenting cells
Effector cells then carry out the attack on the antigen
T cytotoxic (or T killer) cells
B cells (produce antibodies)
Leukocytes

10. Antigen-Presenting Cells Tell the Immune System What to Attack
Eat the invading antigen
Break it down into pieces called epitopes
Put epitopes on the cell surface, attached to MHC II proteins

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12. Antigens Attached to MHC Proteins Can Be “Seen” by Immune Cells
The immune cells have receptors that attach to MHC proteins and “see” the antigen
They also have antigen receptors
Only those T cells whose antigen receptors “fit” the antigen being displayed will respond to it

13. Question
AIDS is an example of a disease in which patients are immunocompromised. Which immune cells are affected in AIDS?
T lymphocytes
B lymphocytes
Antigen presenting cells
Leukocytes

14. Answer
T lymphocytes
As you can see in slide 08, the virus is attaching itself to CD4 receptor sites, located on T cells (T lymphocytes). Only helper T cells have this receptor.

15. MHC I and MHC II Proteins Both Display Antigens
MHC II proteins display antigens eaten by a phagocytic cell
MHC I proteins display antigens made inside an infected cell

16. MHC I and MHC II Proteins Both Display Antigens (cont.)
MHC II proteins tell T helper cells to start an immune response against the antigen
MHC I proteins tell T cytotoxic cells to kill the infected cell before it can infect other cells

17. Where Do Lymphocytes Come From?
Stem cells in the bone marrow or fetal liver
B cells mature in the bone marrow
T cells mature in the thymus
Then they move to the lymph nodes to wait for an antigen-presenting cell to activate them

18. T Lymphocytes Differentiate in the Thymus
T helper cells (CD4+)
CD4 receptors attach to MHC II proteins
Start an immune response
T cytotoxic cells (CD8+)
CD8 receptors attach to MHC I proteins
Kill infected cells

19. Question All but which of the following is true about CD8 receptors?
They can be found on cytotoxic T cells.
They attach to MHC I proteins.
They signal the start of the immune response.
They differentiate in the thymus.

20. Answer c. They signal the start of the immune response.
CD8 receptors do all of those things, but they don’t kick off the immune response (the helper T cell does that). CD8 receptors are found on cytotoxic T cells; as the name implies, they kill the infected cell.

21. Two Kinds of T Helper Cells
TH1 cells
Stimulate the T cytotoxic cells and other phagocytic cells to attack the antigen
TH2 cells
Stimulate the B cells to create antibodies against the antigen

22. TH Cells Release Cytokines
Cytokines are chemicals that control the immune response
Inflammatory mediators: cause fever; attract WBCs to the infection
Growth factors: cause WBCs to divide and mature
Cell communication molecules: used to control activity of other WBCs

23. B Lymphocytes
Like T cells, B cells have antigen receptors
They can only be activated to attack the antigen if a T helper cell shows it to them

24. Activated B Cells Divide into Two Kinds Of Cells:
Memory B cells remain in the body
In the future, they will fight off the antigen without a T helper cell telling them to do so
Plasma cells create antibodies, special proteins designed to attach to that antigen and destroy it

25. Question Which immune cell creates antibodies in response to antigens?
Cytotoxic T lymphocytes
Helper T lymphocytes
Cytokines
B lymphocytes

26. Answer
B Lymphocytes
Remember that antibodies are created in response to antigens. B lymphocytes have antigen receptors and are activated to attack a specific antigen if a T helper cell directs them to do so.

27. Discussion: A lack of B cells A lack of Tc cells A lack of TH1 cells
Which would cause the most severe immune deficiency?
A lack of B cells
A lack of Tc cells
A lack of TH1 cells
A lack of TH2 cells
A lack of macrophages

28. Antibodies or Immunoglobulins
IgG: circulates in body fluids, attacking antigens
IgM: circulates in body fluids; has five units to pull antigens together into clumps
IgA: found in secretions on mucus membranes; prevents antigens from entering the body
IgD: found on the surface of B cells; acts as an antigen receptor
IgE: found on mast cells in tissues; starts an inflammation

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30. Complement Proteins Highly toxic proteins
Circulate in the blood in an inactive form
When an antibody attaches to an antigen, the resulting immune complex can activate complement
Complement then destroys the antigen

31. Discussion: A woman has type a blood…
What antigens does she have on the surface of her red blood cells?
What antibodies against RBC antigens has her body produced?
What will happen if she is given type B blood?
What will happen if her blood is given to a person with type B blood?
What will happen if she is given type O blood?

32. Primary Immune Response
The macrophage must eat the antigen, then present it to TH cells
TH cells must activate B cells
B cells produce antibodies
Then plasma antibody levels rise
This can take 2–3 weeks
Vaccination produces a primary immune response

33. Secondary Immune Response
B memory cells respond to the antigen immediately
Plasma antibody levels rise within days
Booster shots cause a secondary immune response so antibody levels will be high before the disease is encountered

34. Active Immunity vs. Passive Immunity
Scenario:
A woman was bitten by a rattlesnake last summer; she received antiserum against the snake venom, and she survived.
This summer she will be vacationing in the same area
Question:
Should she get a booster shot against snakebite before her vacation?

35. Active Immunity vs. Passive Immunity (cont.)
Scenario:
A woman's baby is HIV-positive
Question:
Does this mean the baby has HIV?
Does it mean the father has HIV?
Does it mean the mother has HIV?

36. Active Immunity vs. Passive Immunity (cont.)
Discussion:
The woman says that since her immunity went to her baby, the baby will not need any vaccinations. Is this correct?

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38. Question Tell whether the following statement is true or false:
Active immunity is achieved much quicker than passive immunity.

39. Answer
False
In active immunity, an individual is exposed to an antigen, the immune response begins, and antibodies are formed in 7–10 days. In passive immunity, antibodies are created outside the host and injected, giving the individual immunity immediately.