8) Immunoregulation

Question 1

Which two surface markers are expressed by Treg cells?

Answer 1

CD4 and CD25

Question 2

Which transcription factor is present in Treg cells?

Answer 2

FoxP3

Question 3

Which cytokine is an important growth factor for Treg cells?

Answer 3

IL-2

Question 4

Treg cells expresses high levels of this molecule that helps to inhibit T cell activation

Answer 4

CTLA-4

Question 5

What cytokine is required for Treg development?

Answer 5

TGF-beta

Question 6

What two things do Treg cells prevent?

Answer 6

they prevent:

1) excessive foreign antigens
2) immune response to self antigens missed by tolerization process

Question 7

this autoimmune disease is characterized by absence of Treg cells

Answer 7

IPEX syndrome

Question 8

What are the three mechanisms of actions for Treg cells?

Answer 8

1) cytokines IL-10 and TGF-beta
2) CTLA-4/B7 interaction
3) consumes IL-2

Question 9

How does CTLA-4/B7 interaction down regulate activation of T cells?

Answer 9

CTLA binds to B7 with greater affinity (B7 normally binds to CD28 of T cells). this interaction prevents an important co-stimulatory signal required for T cell activation

Question 10

How does consuming IL-2 down regulate immune response?

Answer 10

IL-2 is a growth factor for Treg cells, however, it is also a stimulatory cytokine for activated T cells. By consuming available IL-2, this helps down regulate the activity of activated T cells

Question 11

What are the two mechanisms for Ab feedback?

Answer 11

1) Ab helps eliminate Ag –> no further stimulation

2) immune complex (Ab bound to Ag) binds to Fc receptors on B cells thus inactivating them

Question 12

What is the term used to describe unresponsive to antigens?

Answer 12

tolerance

Question 13

What happens when tolerance to self is lost?

Answer 13

autoimmue disease

Question 14

This type of tolerance occurs in primary lymphoid tissues (thymus or BM) and majority of self-reactive lymphocytes are destroyed here.

Answer 14

central tolerance

Question 15

This type of tolerance occurs in the periphery and catches self-reactive lymphocytes that have leaked out of primary lymphoid tissues

Answer 15

periphery tolerance

Question 16

True or False. ALL MHC molecules will present self antigens (both class I and class II).

Answer 16

TRUE. this is why tolerance is important

Question 17

What are three characteristics of tolerance?

Answer 17

1) antigen-specific
2) acquired
3) each of us has the capacity to develop autoimmunity

Question 18

True or False. Mature lymphocytes are easier to tolerize than immature lymphocytes.

Answer 18

FALSE. IMMATURE are easier to tolerize than mature (doesn’t mean mature lymphocytes can’t be tolerized)

Question 19

functional inactivation of viable lymphocytes

Answer 19

clonal anergy

Question 20

death of antigen-specific lymphocytes

Answer 20

clonal deletion

Question 21

What happens when T cells interact with APCs without co-stimulatory signals?

Answer 21

T cell is unresponsive (anergic)

Question 22

True or False. B cells can see non-peptides such as lipids and polysaccharides.

Answer 22

TRUE. these are called thymus-independent antigens

Question 23

What are the two ways B cells are tolerized?

Answer 23

1) clonal deletion

2) receptor editing

Question 24

What is receptor editing?

Answer 24

B cell is given a second chance to rearrange its light chain genes to a different antigen specificity (the first time it recognized self-antigens)

Question 25

Do thymocytes contain TCR?

Answer 25

NO, they do no contain TCR, thus they cannot recognize or respond to antigens

Question 26

What are the four types of populations of T cells found in the thymus?

Answer 26

1) double negative (CD4- CD8-)
2) double positive (CD4+ CD8+)
3) single positive (CD4+)
4) single positive (CD8+)

Question 27

What is eliminated in positive selection?

Answer 27

it eliminates thymocytes that bind to foreign MHC proteins

Question 28

What is eliminated in negative selection?

Answer 28

it eliminates thymocytes that bind to self antigens AND self MHC

Question 29

Positive selection is mediated by…

Answer 29

cortical epithelial cells

Question 30

Negative selection is mediated by…

Answer 30

DCs at corticomedullary junction

Question 31

After the completion of both positive and negative selection, what kind of thymocytes are left?

Answer 31

only ones that recognize to foreign antigens and self MHC

Question 32

What is the importance of autoimmune regulator (AIRE) gene?

Answer 32

allows for negative selection for self-reactive T cells to “tissue-specific” self antigens e.g. insulin expressed by thymic DCs

Question 33

What happens when there’s a mutation in the AIRE gene?

Answer 33

widespread autoimmune disease

Question 34

tissue-specific proteins are under the regulation of…

Answer 34

AIRE