Immunity Regulation

Question 1

How does the immune system deal with invaders?

Answer 1

1. Ab response to prevent attachment and entry of microbes (extracellular organisms)
2. T cell-mediated response that mediate the activation of APCs and killing infected cells with intracellular microbes

Question 2

What does the helper T cell do after activation?

Answer 2

1. Secrete cytokines (IL-4) that help B cells produce Abs (TH2)
2. Secrete IFN that stimulates complement (TH1)

Question 3

T helper (TH) cells

Answer 3

CD4+ and bind to MHC class 2

TH3: TGF-beta
TH17: IL-17A

Question 4

T Cytotoxic cells (CTL)

Answer 4

CD8+ and binds to MHC class 1

TC1: IFN
TC2: IL-4 and IL-5

Question 5

Cytotoxic T lymphocytes kills target cell by the release of what?

Answer 5

Perforin
Granzymes

Question 6

Perforin

Answer 6

A pier forming protein that causes cell to burst

Question 7

Granzymes

Answer 7

Proteases that induce apoptosis (programmed cell death)

Question 8

Cell death

Answer 8

Normal process involving old, surplus or abnormal cells that can interfere with normal tissue function or induced by infection, toxicity and trauma

Question 9

Apoptosis (PCD)

Answer 9

Programmed cell death
Activated only when cell must die
Ex: old, surplus, abnormal cell

Question 10

Why are the 2 pathways for apoptosis cell death

Answer 10

Intrinsic: mitochondrion (oxidants, radiants)
Extrinsic: death receptor - CD95 (TNF, CD95L)

Question 11

Necrosis

Answer 11

Cells severely damaged by trauma, toxicity or microbial invasion
Largely unregulated, nflammatory process

Question 12

What can trigger necrosis or apoptosis?

Answer 12

Microbial agents

Question 13

How does CTL kill infected target which ways?

Answer 13

Directly and indirectly

Question 14

Direct CTL apoptosis

Answer 14

Interaction of ligand (CD95L) on T cells and receptor (CD95) on infected target
Leads to apoptotic signal

Question 15

Indirect CTL apoptosis

Answer 15

Release of proteilytic enzymes such as granzymes and perforins

Question 16

Outcomes of apoptosis (PCD)

Answer 16

Clumping of chromatin
Apoptotic bodies
Cell bedding
Nuclear fragmentation
Loss of organelles

Question 17

How are T cells classified?

Answer 17

1. Type of secretion
2. Expression of surface molecules (CD4 and CD8)

Question 18

Which cytokines activate macrophages?

Answer 18

IL-2, IFN-Y, IFN-a/b, TNF-a, TNF-b, GM-CSF

Question 19

Which cytokines suppress macrophages?

Answer 19

IL-10, IL-4, IL-13, TGF-b

Question 20

Tolerance

Answer 20

The state of unresponsiveness that involves T and B cells
1. Central (self, clonal deletion)
2. Peripheral (in response to Ags, clonal anergy)

Question 21

Central/ self tolerance

Answer 21

Develops early in life to preserve our body from attack by our own immune system
T cells responsive to own cells are deleted I’m thymus

Question 22

Example of self tolerance

Answer 22

Bovine dizygotic (non identical twins)
Blood mixed between 2 calves because reactive T cells in twins were deleted in the thymus early in life

Question 23

How are self Ags recognized in the thymus?

Answer 23

Ags are expressed on surface of thymic epithelium by promiscuous gene expression
Ags transported from outside thymus by DCs/MACs

Question 24

Negative selection of T cell tolerance

Answer 24

Elimination of T cells that don’t recognize MHC and are reactive to self Ags

Question 25

Positive selection of T cell tolerance

Answer 25

Selection of T cells that react moderately with MHC and aren’t reactive to self Ags

Question 26

What mechanisms affect immune response?

Answer 26

1. Inadequate immune response
2. Excessive immune response leading to autoimmunity/ hypersensitivity
3. Slowly metabolized Ags
4. Form of Ag (polymeric or momomeric)
5. Type of APC
6. Abs or Ag-Ab immune complexes

Question 27

Ag-Ab immune complexes

Answer 27

Excessive production of Abs trigger an inhibitory feedback mechanism
In some diseases excess Ags in blood form complexes

Question 28

Consequences if Ag-Ab immune complexes

Answer 28

Deposition of organs, increased infection due to inhibition of Ab synthesis
Maternal Abs interfere with vaccination of newborn through neg feedback process