Restraining The Immune System Flashcards Preview

Immunology Exam Two > Restraining The Immune System > Flashcards

Flashcards in Restraining The Immune System Deck (52):
1

What kind of T cells function to restrain the immune system?

Regulatory T cells (inducible and natural Tregs)

2

Activated helper T cells secrete what substances to activate the immune system?

TNF and IFN-gamma

3

Activated regulatory T cells secrete what substances to restrain the immune system?

TGF-beta and IL-10

4

What is TGF-beta?

Transforming growth factor beta

5

What is the function of TGF-beta?

Reduces proliferation and CTL killing

6

To where does TGF-beta bind?

Receptors on T cells

7

What is the function of IL-10?

Blocks co-stimulatory signals like CD28 making activation more difficult, also reduces proliferation

8

To where does IL-10 bind?

Receptors on T cells

9

What is the result of B7 binding to naive T cell's CD28?

Co-stimulation and activation

10

What is the result of CTLA-4 binding all the B7 co-stimulatory molecules?

Blockage of co-stimulation and activation

11

What binded grouping is mostly seen early in an infection?

B7 to CD28 to act as a co-stimulator

12

What binded grouping is mostly seen after a battle has been going on for a while?

B7 to CTLA-4 makes it harder to reactivate T cells

13

What kind of T cells live a relatively long time?

Naive ones (spend their whole life looking for cognate antigen)

14

When does a T cell's longevity decline?

When activated

15

Why does a T cell's longevity decline once activated?

Fas proteins are now more sensitive due to being activated multiple times which leads to cell death

16

Why do virgin T cells come with increased longevity?

Fas proteins are insensitive to ligation and therefore avoid cell death

17

Once an invader has been vanquished, around what percentage of T cells die off?

Over 90%!

18

Why must immune responses be able to be turned off once an invader has been dealt with?

Prevention of autoimmune damage

19

What mainly controls the activation level of the immune response?

Amount of foreign antigen present

20

What are the functions of commensal bacteria found in our intestines?

Help digest food
Produce vitamins
Protect us from pathogens by out-competing them

21

Why is it possible that some bacteria eventually are able to breach the normal barrier into tissue?

Such a large surface area (around 200 square meters)

22

What makes the macrophages located beneath the intestinal wall special?

They don't secrete cytokines to avoid signaling a full blown invasion of the GI tract (can lead to inflammation, diarrhea, etc.)

23

What is the function of macrophages seen beneath the intestinal wall?

Phagocytize invaders that attempt to enter tissue

24

What is the major type of antibody seen in the intestines and the tissues below?

IgA

25

What is the specific function of IgA in the GI tract?

Bind and neutralize invaders that attempt to enter the tissues

26

When IgA finds invaders leaving the GI tract, what is done with them?

Send back to the intestinal tract where they are flushed out in the stool

27

Can IgA fix complement?

No

28

Can IgA stimulate inflammation?

No (good for the GI tract then)

29

What two major things act against the immune system with restraint?

Specialized macrophages and IgA

30

During non-battle conditions, what are the epithelial cells of the intestine producing to induce regulatory T cells?

TGF-beta

31

What is the effect of TGF-beta in the intestine?

Causes cells in Peyer's patches to become regulatory T cells

32

What is the purpose of the cytokines released by regulatory T cells in the intestines?

Encourage a calmer mucosal immune system

33

During battle conditions, epithelial cells of the intestine are producing TGF-beta, and what are the dendritic cells producing?

IL-6

34

During battle conditions, T cells commit to becoming what cells?

Th17

35

Are iTregs CD4+ or CD8+?

CD4+

36

iTregs develop from what cells under influence of TGF-beta from the intestine?

Th0 (naive T cells)

37

What are the two subtypes of iTregs?

Tr1 and Th3

38

Which has a higher affinity for B7: CD28 or CTLA-4?

CTLA-4 (1000's X)

39

What is the function of CD28?

When activated, amplifies the signal and lowers the number of TCR crosslinks needed for activation

40

Why is it easy to discard of obsolete weapons for the immune system when the invader is dealt with?

Most have short lifespans anyway

41

Which immune cells live the longest?

Macrophages (for months)

42

Why do macrophages tend to live longer than other types of immune cells?

NKCs make IFN-gamma which keeps them activated

43

Which immune cells live the shortest lifespans?

Neutrophils (few days)

44

When are macrophages able to go back to a resting state?

When NK cells die off and the supply of IFN-gamma decreases

45

How long do dendritic cells usually live?

About a week once they reach the lymph node

46

What is the lifespan of a plasma cell?

Five days (of hard labor producing antibodies)

47

What kind of immune cells are the exception to the "short life" rule?

T cells (or memory cells)

48

How does the body rid itself of obsolete (experienced) T cells after an attack?

Activation-induced cell death

49

What death receptor is seen on the surface of cells?

Fas receptor protein

50

What binds to the Fas receptor protein causes apoptosis?

Fas ligand

51

Which is found on the natural kill or killer T cell: Fas receptor protein or Fas ligand?

Fas ligand

52

What type of T cell expresses more Fas protein?

Experienced