Cellular Immune Response

Question 1

What are the main effects of Cytotoxic T cell activation by receptors and/or signals?

Answer 1

• infected cells are killed (Apoptosis)

- infected cells are activated and destroy the intracellular organism

Question 2

What is a superantigen?

Answer 2

…

Question 3

How does a superantigen induce the immune response?

Answer 3

…

Question 4

What are the three major classes of effector T cells?

Answer 4

…

Question 5

What is the cellular immune response provided by?

Answer 5

T cells

Question 6

What is the cellular immune response used to provide immunity to?

Answer 6

• intracellular bacteria
• intracellular virus
• fungi
• protozoa
• tumors

Question 7

When do T cells recognize antigen?

Answer 7

only when it is presented on the surface of APCs by self MHC molecules

Question 8

What is the intrinsic pathway of T cell cytotoxicity Apoptosis?

Answer 8

granzymes produced and released by T cell -> granzymes enter cell through perforin channels and enter mitochondria -> Cytochrome C released -> apoptosome -> caspase 9 activation -> effector caspase activation (caspases -3, -6, -7) -> DNA fragmentation, cytoskeletal disruption, chromatin disruption -> apoptosis
— T cell binds to MHC I -> produces + releases granzymes -> granzymes travel through perforins -> caspase-3 -> DNA fragmentation -> Apoptosis

Question 9

What is the extrinsic pathway of T cell cytotoxicity Apoptosis?

Answer 9

CD95L binds to CD95 receptor on cell membrane -> release of DISC which activates caspase 8 -> effector caspase activation (caspasees -3, -6, -7) -> DNA fragmentation, cytoskeletal disruption, chromatin disruption -> apoptosis
— T cell binds to MHC I -> produces + releases CD95-L -> binds to CD95 (Fas) receptor -> caspase-8 activation -> caspase-3 activation -> DNA fragmentation -> Apoptosis

Question 10

What are initiator caspases? What are they activated by?

Answer 10

2, 8, 9, 10, 14

activated by multimolecular death complexes

Question 11

What are effector caspases? What do they do?

Answer 11

3, 6, 7

Break down cellular structures

Question 12

What are inflammatory caspases and what are they activated by?

Answer 12

1, 4, 5, 11

activated by multimolecular inflammasomes

Question 13

What are the major morphological features of cell death by apoptosis?

Answer 13

Normal cell ->
Clumping of chromatin, blebbing, loss of organelles ->
nuclear fragmentation, apoptotic bodies ->
apoptotic bodies

Question 14

What are the three main mechanisms of cell-mediated cytotoxicity? How long do they take?

Answer 14

• NK-mediated cytotoxicity - 24hrs
• ADCC activity - 6hrs
• T-cell mediated cytotoxicity - 10mins

Question 15

Which mechanism(s) of cell-mediated cytotoxicity is/are MHC restricted?

Answer 15

T cell mediated cytotoxicity

Question 16

Which mechanism(s) of cell-mediated cytotoxicity is/are Antigen specific?

Answer 16

• ADCC activity

- T cell mediated cytotoxicity

Question 17

What is the fastest mechanism of cell-mediated cytotoxicity? What is the cytotoxic cell?

Answer 17

• T cell mediated cytotoxicity 10mins

- Primed T cells

Question 18

What is the slowest mechanism of cell-mediated cytotoxicity? What is the cytotoxic cell?

Answer 18

• NK-mediated cytotoxicity 24hrs

- NK cells

Question 19

How are macrophages activated by the cellular immune response?

Answer 19

mycobacteria -> APC -> produces IL-12 and IFN-y -> Th1 cell -> produces IFN-y and IL-2 -> activated macrophage

1. Antigen is phagocytosed by macrophages or dendritic cells. (APCs)
2. Antigen is processed and then presented on the cell surface
3. Costimulation with Th1 cell
4. Th1 produces interleukin-2 and Interferon-y
5. Activation of macrophage

Question 20

What happens when macrophages are activated by the cellular immune response?

Answer 20

bacteria inside the macrophage are destroyed