Tcell responses and cell mediated immunity

Question 0

negative selection
occurs when?
how?

Answer 0

Occurs after positive selection in the medularry region of thymus.

T cells that bind MHC class I/peptide or MHC II/peptide stringly (ie high affinity) are killed by apoptosis.

Question 1

positive selection is achieved by

Answer 1

T cells that bind MHC I or MHC II + self peptide SURVIVE

T cells that do not find a peptide/MHC die

Question 2

central tolerance
what?
how?

Answer 2

process by which self-rxn T cells are clonally deleted in primary lymphoid tissue.

occurs via apoptosis when binding to an self antigen strongly…essentially negative selection.

Question 3

Peripheral tolerance
what?
how?

Answer 3

silencing of auto reactive T cells in the periph

occurs via:

1. ignorance - auto reactiv T cells wont be activated in certain tissues
2. Anergy - auto rxn T cells that bind a peptide/MHC in the abscence of co stimulators (like form a non-APC) will not be activated
3. regulatory T cells xpressing cd4,, cd25 (IL2 receptor) and transcription ffactor Foxp3. shut down immunity after antigen elimination and/or surpress auto-reactiv cells

Question 4

what is cd 25

Answer 4

IL-2 receptor

Question 5

fxns of IL 2 (3)

Answer 5

1. induces clonal T cell expansion
2. alters cell surface molecules to control ttraficking from secondary lymphoid organs
3. expresses membrane protiens like cd154 that trigger other immune cells

Question 6

3 effector t cells of cellmediated immune response

Answer 6

1. cd8+ cytotoxic T cells
2. cd4+ helper T cells
3. cd4+ t regulatory cells

Question 7

cd8+ ctls recognise ____ and ______

Answer 7

MHC class I with antigen, and kill cells with thos pathogens

Question 8

how can CTLs kill (3 mechanisms)

Answer 8

1. release perforin and granzymes to destroy target cell membrane
2. releasing factor like TNF alpha or IFN gamma,
3. expressing Fas-L, which binds Fas of tartget cell, triggering apoptosis.

CTLs can use any of these mechanisms, kill the cell, and then move on to more targets.

Question 9

what are Th0, Th1, Th2, and Th17 cells?

Answer 9

They are all cd4 + helper T cells. Early activated ones are Th0. Th1, Th2, and Th17 are more specialized.

Question 10

all CD4+ T cells recognize _____ _____ ___ peptide complexes

Answer 10

MHC class II

Question 11

Th1 T cells predominantly:

Answer 11

mediate innflammatory response (activate macrophages) by producing IFN gamma and TNF.

Also: secrete hematopoetic growth factors for macrophae development

Question 12

What cytokine is associated with development of Th1 Cells?

Answer 12

IL-12

Question 13

What are functions of IL-12? (2)

Answer 13

1. stimulate IFN gamma production in NK and T cells (increases cytotoxic activity
2. Stimulates Th1 differentiation from early, mature Th0 cells

Question 14

Th2 cell fx(s)

Answer 14

produce IL-4, IL-5, and IL-13 to stimulate B cell proliferation and Ab secretion

Question 15

Th17 cells fx(s)

Answer 15

Recruit neutrophils
Produce large amounts of IL-17

(are these fxs two related???)

Question 16

IFN gamma is produced by _____ and ______

and acts to activate _______ and stumulate ________ ________

Answer 16

produce byy NK and T cells (Th1)

actiaves macrophages to kill pathogens and stimulates Ab responses.

Question 17

Th1 cells make 2 hematopoetc growth factors…they are:

Answer 17

granulocyte-macrophage stimulatory factor (GM-CSF) and IL-3

Question 18

GM-CSF and IL-3 act to:

Answer 18

increase production and release of macrophages from bone marrow into blood

Question 19

Th1 cells release TNF to help activate macrophages to kill pathogens. TNF also plays a role in…

Answer 19

1. Altering surface of endothelium to promote macropahge adhesion (this is inflammation)
2. neutrophil activation
3. fever response in the hypothlamus
4. Acute phase protien respose in liver (innate response)
   a few other things too…..

Question 20

IFN gamma is produced by Th1 cells to activate macropages, but also prevents induction of _______ cells and promotes production of cytokines that increase _____ differentiaiton.

Answer 20

Prevents induction of Th2 cells and
promotes cytokines tthat increase Th1 cell differentiation. -»
This is a positive feedback loop that reinforces the Th1 response.

Question 21

The T cell most effective at inducing Ab production from B cells is the :

Answer 21

Th2 cell

Question 22

not only can Th2 cells induce Ab production in B cells but they can also (2)

Answer 22

1. Switch the isotype of Ab produced

2. and promote maturation of the Abs

Question 23

Other than B cells, Th2 cells can induce production of ________. (using IL-5)

Answer 23

Eosinophils

Question 24

The main function of CD4+ Reg T cell is to _______________

Answer 24

Surpress immune responses

Question 25

CD4+ Treg cells use FoxP3. Loss of Fox P3 leads to:

Answer 25

Autoimmunity

Question 26

Name 3 secondary lymphoid organs

Answer 26

spleen
lymph nodes
peyers patchs

Question 27

Primary lymphoid organs

Answer 27

Bone marrow, Thymus

Question 28

A naive cell is a:

Answer 28

T or B cell that has not yet encountered its specific antigen and continue to circulate through the body

Question 29

Lymphocytes eneter lymph nodes via _____ _____ ________s by binding to ____________ on the endothelial surfaces of blood vessels.

Answer 29

High endothelial venules

addressin(s)

Question 30

Unique to MALT, lymphocytes stimulated in a mucosal site can:

Answer 30

Travel to other mucosal sites to protect from incoming infection via ‘homing’ molecules.

Question 31

fx of TGF Beta (2)

Answer 31

inhibits inflammation, stimulates Th17 differentiation

Question 32

fx of IFN gamma

Answer 32

activates macrophages, stimulates Ab response

Question 33

type I IFN’s (a and B)

Answer 33

activate antiviral state. activate NK cells. B increases MHC I expression