T Cell-Mediated Immunity – Activation of T Cells by Cell-Associated Antigens

Question 1

types of intracellualr microbes combated by t cells

Answer 1

those in phagocytes and those in non-phagocytes

Question 2

examples of microbes in phagocytes

Answer 2

Question 3

examples of microbes in non-phagocytes

Answer 3

Question 4

Induction and effector phases of cell-mediated immunity diagrammed

Answer 4

Question 5

where does Ag recognition occur?

Answer 5

peripheral LN

Question 6

do all effector T cells leave the LN?

Answer 6

some stay to simulate B cells

Question 7

Steps in the activation of T lymphocytes diagrammed

locations of these steps?

Answer 7

Question 8

what happens to effector cell population when infection cleared?

Answer 8

die off aside from memory cells (contraction/homeostasis)

Question 9

what are CD4/8

Answer 9

coreceptors to help recognize the MHC complexes

Question 10

Antigen recognition and costimulation
just TCR and MHC?
helps with?

Answer 10

occurs with TCR complex not just MHC to TCR and CD4/8, required interactions for stimulation
help with adhesion and signal transduction

Question 11

TCR complex interactions diagrammed

Answer 11

Question 12

first activating signal of t cells

Answer 12

Ag recogniton via TCR and CD4/8 to MHC causing the signal transduction in the t cell with phos/dephos pathways to induce TFs and gene expression for expansion and effector function

Question 13

Adhesion molecules on T cells that stabilize binding to APCs

Answer 13

LFA-1 is an integrin protein expressed on t cell mem that binds the ICAM ligand on APC to stabilize adhesion

Question 14

table with TCR receptor complex components and their ligands and functions and where they occur 
CD3
CD4
CD8 
CD28
CTLA-4
PD-1
LFA-1

Answer 14

Question 15

Role of costimulation in T cell activation:
signals/ligands from activated APC
without these?

Answer 15

B7 ligand on APC will bind CD28 on the T cells
this is required for a t cell response, only activated APC express B7 (due to innate immunity response or microbes), WITHOUT B7 NO RESPONSE/ TOLERANCE

activated APC also secrete IL-2
BOTH ACTIONS CAUSE THE T CELL TO SECRETE IL-2 AND ACTIVATE (IL-2 TO IL-2R ON T CELL=AUTOCIRNE), CAUSES PROLIF AND DIF

Question 16

Inhibitory receptors of T cells, why needed? interactions causing this?

Answer 16

necessary for limiting/terminating immune responses
B7 to CTLA-4 receptor=inhibitory, mediates function of Ts
PD-L2 to PD1=inhibition

Question 17

MHC I and II dual action

Answer 17

APCs that engulf virus-infected cells (source of class II MHC peptides) and also are infected themselves (source of class I MHC peptides) will have antigens presented by both classes I and II MHC molecules.

These APCs engage both CD4+ T cells (via Class II MHC) and CD8+ T cells (via Class I MHC).

In this case the CD4+ T cell helps activate the CD8+ T cell

important with some viral infections

Question 18

T cell expression following recognition of antigens and costimulators
graph of proteins produced and their functions

Answer 18

cascade of gene expressions will drive the prolif and dif of t cells

Question 19

Signal transduction pathways in T lymphocytes

Answer 19

TCR complex will phos adaptor proteins via CD3 and ITAM to cause signal transduction into the cytoplasm via cascades of phos/dephos producing intermediates and ultimately active enzymes to produce TFs that activates genes for genes for cytokines, cytokine receptors, cell cycle inducers, and other effector molecules

Question 20

active enzymes and TFs of Tcell signal transduction

Answer 20

Question 21

cyclosporine and rapamycin actions

Answer 21

used in grafting procedures to prevent reject

cyclo will inhibit calcineurin to prevent T cell expanse/ function and rapamysin will inhibit Akt/ mTOR to do the same

Question 22

Secretion of cytokines and expression of cytokine receptors with t cell activation/ role of IL-2 and IL-2R in proliferation

Answer 22

Question 23

principal function IL-2

Answer 23

survival and proliferation of antigen-specific T cells

Question 24

Expansion and decline of T cell responses

Answer 24

both Ag-specific Th and Tc rapidly expand (from relatively small naive population) in infection but then decline once infection cleared to restore homeostasis (memory cells remain)

Question 25

why would more CD8 effectors be needed?

Answer 25

these take the pathogen on one on one whereas the CD4 uses cytokines and plays a less direct role on defenses

Question 26

immunodominant Ag’s, why would we need many types of receptors due to these?

Answer 26

these bind very strongly to MHC complexes, need a variety of receptors so we can survey for other Ag too

Question 27

Development of effector CD4+ T cells

Answer 27

some also become memory cells to induce a rapid response with future exposures

Question 28

Roles of CD40L and cytokines in effector functions of CD4+ helper T cells

Answer 28

CD40 is ligand found on active Th that can activate macrophages and b lymphocytes
binding to receptors on either will stimulate cytokine production and the effector functions of each cell

Question 29

Migration of naïve and effector T lymphocytes molecule classes used

Answer 29

selectin
integrin
chemokine receptor

Question 30

where a naive t cells

Answer 30

peripheral LN

Question 31

naive t cell basic migration pattern

Answer 31

migrate between blood/lymphoid tisse back and forth until exposed to Ag, then activated/ migrates to site of infection for effector function

Question 32

exit molecule of t cell migration from LN (responsible for the back an forth)

Answer 32

S1P: higher con. in blood> causes lower con. receptors on t cells in blood and migration to the LN where S1P is low, this increases the receptor con. and they move back into blood

Question 33

naive t cells: homing receptors, ligand on endothelial cell and the function of the binding of the two (for each class of molecules involved)

Answer 33

Question 34

activated t cells (effector and memory): homing receptors, ligand on endothelial cell and the function of the binding of the two (for each class of molecules involved)

Answer 34