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Immunology Exam Two > Restraining The Immune System > Flashcards

Restraining The Immune System Flashcards

1
Q

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

A

Regulatory T cells (inducible and natural Tregs)

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2
Q

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

A

TNF and IFN-gamma

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3
Q

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

A

TGF-beta and IL-10

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4
Q

What is TGF-beta?

A

Transforming growth factor beta

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5
Q

What is the function of TGF-beta?

A

Reduces proliferation and CTL killing

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6
Q

To where does TGF-beta bind?

A

Receptors on T cells

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7
Q

What is the function of IL-10?

A

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

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8
Q

To where does IL-10 bind?

A

Receptors on T cells

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9
Q

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

A

Co-stimulation and activation

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10
Q

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

A

Blockage of co-stimulation and activation

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11
Q

What binded grouping is mostly seen early in an infection?

A

B7 to CD28 to act as a co-stimulator

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12
Q

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

A

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

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13
Q

What kind of T cells live a relatively long time?

A

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

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14
Q

When does a T cell’s longevity decline?

A

When activated

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15
Q

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

A

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

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16
Q

Why do virgin T cells come with increased longevity?

A

Fas proteins are insensitive to ligation and therefore avoid cell death

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17
Q

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

A

Over 90%!

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18
Q

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

A

Prevention of autoimmune damage

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19
Q

What mainly controls the activation level of the immune response?

A

Amount of foreign antigen present

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20
Q

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

A

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

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21
Q

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

A

Such a large surface area (around 200 square meters)

22
Q

What makes the macrophages located beneath the intestinal wall special?

A

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

23
Q

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

A

Phagocytize invaders that attempt to enter tissue

24
Q

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

A

IgA

25
Q

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

A

Bind and neutralize invaders that attempt to enter the tissues

26
Q

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

A

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

27
Q

Can IgA fix complement?

A

No

28
Q

Can IgA stimulate inflammation?

A

No (good for the GI tract then)

29
Q

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

A

Specialized macrophages and IgA

30
Q

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

A

TGF-beta

31
Q

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

A

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

32
Q

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

A

Encourage a calmer mucosal immune system

33
Q

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

A

IL-6

34
Q

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

A

Th17

35
Q

Are iTregs CD4+ or CD8+?

A

CD4+

36
Q

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

A

Th0 (naive T cells)

37
Q

What are the two subtypes of iTregs?

A

Tr1 and Th3

38
Q

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

A

CTLA-4 (1000’s X)

39
Q

What is the function of CD28?

A

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

40
Q

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

A

Most have short lifespans anyway

41
Q

Which immune cells live the longest?

A

Macrophages (for months)

42
Q

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

A

NKCs make IFN-gamma which keeps them activated

43
Q

Which immune cells live the shortest lifespans?

A

Neutrophils (few days)

44
Q

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

A

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

45
Q

How long do dendritic cells usually live?

A

About a week once they reach the lymph node

46
Q

What is the lifespan of a plasma cell?

A

Five days (of hard labor producing antibodies)

47
Q

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

A

T cells (or memory cells)

48
Q

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

A

Activation-induced cell death

49
Q

What death receptor is seen on the surface of cells?

A

Fas receptor protein

50
Q

What binds to the Fas receptor protein causes apoptosis?

A

Fas ligand

51
Q

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

A

Fas ligand

52
Q

What type of T cell expresses more Fas protein?

A

Experienced

Immunology Exam Two (5 decks)

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