Adaptive immunity Cell-Mediated (complete)

Question 1

what is the B-cell antigen receptor

Answer 1

a membrane bound immunoglobin (two heavy chains, two light chains)

Question 2

what kinds of regions do the B and T cell antigen receptors have

Answer 2

proximal constant regions, and variable distal regions

just like antibodies

Question 3

what is DiGeorge syndrome

Answer 3

when an individual has no T-cells, subject to many overwhelming infections

Question 4

how are naive T cells activated

Answer 4

coming into contact with mature activated dendritic cells that have their MHC/antigen complex and lots of B7 molecules

Question 5

what happens once a T-cell is activated

Answer 5

they proliferate and differentiate into effector T-cells that destroy or eliminate the antigen once they come into contact with it again

Question 6

the first signal a T-cell needs to become activated is

Answer 6

the binding of the MHC/Antigen complex binding to the T-cell antigen receptor from a dendritic cell

Question 7

the second signal that a T-cell needs to become activated is…

Answer 7

costimulatory signal

Question 8

what are the most important costimulatory factors that assist in the activation of T-cells

Answer 8

B7-1 and B7-2 on dendritic cells, interacting with CD28 on T-cells

Question 9

What is the function of T-helper cells

Answer 9

activate antigen producing B-cells
recruit and activate phagocytes
activate eosinophils, basophils and mast cells

Question 10

What happens to the T-cells once the immune response has ended

Answer 10

they must return to normal levels (controlled by cytokines)

Question 11

does the T-cell receptor (TCR) have cytoplasmic tails with any function

Answer 11

their cytoplasmic tails have no signaling function

Question 12

since the cytoplasmic tails of TCR have no signaling function, how does the TCR send signals once it has bound

Answer 12

they have CD3

Question 13

what is CD3

Answer 13

6 chains that are bound to the TCR with ITAM in the cytoplasm

Question 14

what is ITAM

Answer 14

a part of the CD3 of TCRs
Immunoreceptor Tyrosine-based Activation Motifs
the part that signals to the cell when the TCR has bound an antigen/costimulator

Question 15

the BCR (B-cell receptor) is immunoglobin that is membrane bound, what is the structure of the TCR (T-cell receptor)

Answer 15

2 immunoglobin domains that aren’t identical

it is an alpha-beta heterodimer with two proximal constant regions, and two variable distal regions

Question 16

what are the three hypervariable regions of the variable region of the TCR. and what is their function

Answer 16

CDR1, CDR2, and CDR3

these contact the peptide-MHC complex

Question 17

what are the four sources of variability to the TCR

Answer 17

1. different V and J segments of the alpha chain
2. different V, D, and J segments of the beta chain
3. different combinations of the alpha and beta chains
4. variability of the junctions between alpha and beta

Question 18

what does positive selection of T-cells get rid of

Answer 18

those T-cells with weak binding to the Self-peptide/self-MHC complex

Question 19

what does negative selection of T-cells get rid of

Answer 19

those T-cells with too strong of a binding to self-peptide/self-MHC complex

Question 20

the three parts of the variable region of TCRs each bind to what

Answer 20

CDCR1 binds to the MHC molecule
CDCR2 binds to both the MHC and the peptide/antigen
CDCR3 binds to the peptide/antigen

Question 21

of the three parts of the variable region of TCRs, which one is the most variable

Answer 21

CDCR3 the one that binds the peptide/antigen

Question 22

Where do the coreceptors (CD8 and CD4) on T-cells bind to the MHC/antigen complex

Answer 22

they bind to the MHC

Question 23

what does the binding of CD8 and CD4 do for the binding between the TCR and the Antigen MHC complex

Answer 23

it increases the avidity of the binding

and helps the T-cell bind to the right MHC class

Question 24

what class of MHC does the CD8 of T-cells bind to

Answer 24

Class 1

Question 25

what class of MHC does the CD4 od T-cells bind to

Answer 25

Class 2

Question 26

what does CTLA4 do, and what happens if you don't have it

Answer 26

it doesn't cause an increase in CD40L and there fore CD28 on the T-cell. This keeps the T-cell from expressing out of control. in mice that didn't have CTLA4, they died of lymphoproliferative diseases

Question 27

What are the different types of T-cells that can come from CD4 T-cells

Answer 27

Th1 Th2 TREG TH17

Question 28

what cytokine is associated with TH1 T-cells

Answer 28

IFN-y

Question 29

what do TH1 T-cells do

Answer 29

``` activate: macrophages NK cells CD8 T-cells (attacks viruses, intracellular bacteria) ```

Question 30

What cytokine is associated with TH2 cells

Answer 30

IL-4, IL-5, and IL-13

Question 31

what do TH2 cells do

Answer 31

activate: eosinophils, basophils, and mast cells (attacks worms and bloodsucking insects)

Question 32

What cytokine is associated with TH-17 T-cells

Answer 32

IL-17

Question 33

what do TH-17 cells do

Answer 33

activate neutrophils | attacks extracellular bacteria and fungi

Question 34

What cytokine is associated with TREG cells

Answer 34

IL-10, TGF-beta

Question 35

what do TREG cells do

Answer 35

activate dendritic cells | inhibits other effector T-cell types

Question 36

what do most CD8 T-cells differentiate into

Answer 36

cytotoxic T-cells

Question 37

what cytokine do cytotoxic T-cells produce, and what do they do

Answer 37

IFN-y (upregulates MHC class 1 and immunoproteasome) TNF (can activate apoptosis in some cells) Chemokines (attrack other immune cells)

Question 38

What are the cytotoxic mechanisms of Cytotoxic T-cells

Answer 38

1. Perforin 2. granzymes 3. Fas ligand

Question 39

what causes perforin and granzymes to be secreted from Cytotoxic T-cells

Answer 39

the binding of the T-cell to the MHC/antigen complex causes a release of Ca++. this causes the release of Perforin and granzymes

Question 40

how does perforin kill cells

Answer 40

creates pores in the cell membrane, which allows the granzymes to enter

Question 41

how do granzymes kill cells

Answer 41

they enter the cell through perforins and cleave caspase 3 and Bid. these cause DNA fragmentation, and inactivates cellular repair

Question 42

the binding between cytotoxic T-cells and the target cell is transient, but what can cause it to be stronger

Answer 42

LFA-1 and ICAM interactions (these also help focus the secretory apparatus toward the target cell)

Question 43

how do cytotoxic T-cells prevent perforination of themselves that would lead to their own destruction

Answer 43

the vesicles that contain the perforin and granzymes have Cathepsin B on their membrane, and when the vesicle makes it to the cell membrane, they remain at the cell membrane and prevent the fusion of perforin to the cell

Question 44

what leads to the decrease of T-cells after an immune response to maintain homeostasis

Answer 44

they are programmed to die unless they receive survival signals (cytokines, costimulatory signals)

Question 45

what is lymphopenia

Answer 45

low lymphocyte levels in the blood

Question 46

what can cause lymphopenia

Answer 46

viral infection or age