T-Cell activation, differentiation + memory

Question 1

How is the adaptive immune repose initiated?

Answer 1

by interaction between naïve T-cell and antigen presenting cell (APC)

Question 2

How are APCs activated?

Answer 2

~ by pattern recognition receptors @ infection site
~ the processed antigen is presented as peptides on APC PM in the groove of MHC class I and II mol.
~ APC migrate from tissue to lymph nodes + spleen

Question 3

Activation of T-cells

Answer 3

Antigen recognition:

1) interaction of TCR-CD3 complex w/ MHC peptide
2) co-stimulation signal via CD28 + co-stimulatory ligands on dendritic cells
3) soluble cytokines

Question 4

Name the types of co-stimulation.

Answer 4

~ positive
~ negative
~ absent

Question 5

Positive co-stimulation

Answer 5

CD28 + ICOS receptors = t-cell activation

Question 6

Negative co-stimulation

Answer 6

CTLA-4 + PPI + BTLA receptors = t-cell deactivation

Question 7

Absent co-stimulation

Answer 7

= anergy/unresponsiveness, which causes:

1) APCs prevented from up regulating CD80/86
2) anergic T-cells fail to respond even when co-stimulated
3) blockage of CD28 = more anergy

Question 8

IOCS

Answer 8

maintains activity of differentiated T-cells + their responses

Question 9

CTLA-4

Answer 9

down regulation of T-cell responses

Question 10

How can cytokines be influenced by an infection?

Answer 10

~ some exotoxins (gram -ve bacteria) behave as super antigens and activate release of cytokines in macrophages and T-cells
~ causes polyclonal T-cell activation of all specificities
~ done as a diversion away from exotoxin-producing pathogen

Question 11

Superantigen

Answer 11

can simultaneously bind to Vbeta of TCR + alpha chains of MHC class II which allows it to bypass the normal TCR antigen specificity rules

Question 12

What causes T-cell proliferation?

Answer 12

~ activation of naïve T-cell increase secretion of IL-2 + its receptor (autocrine signalling)
~ this causes the cell to divide multiple times creating a population of effector and memory cells

Question 13

Name the stages of T Helper differentiation.

Answer 13

1) PRR binding by pathogen antigens stimulates secretion of cytokines
2) cytokines bind to receptors on CD4+ T-cells + influence differentiation (under control on master regulator)
3) different pathogens stimulate different T(H) subsets

Question 14

T(H)1

Answer 14

~ cell mediated immunity
~macrophage activation
~ inflammation
~ IL-12 + IL-18

Question 15

T(H)2

Answer 15

~ humoral immunity
~ allergic + anti-helminth responses
~ IL-4

Question 16

T(H)17

Answer 16

~ inflammation

~ IL-1 + TGF-beta

Question 17

T(FH)

Answer 17

a.k.a. folicular helper cell
~ B-cell help in germinal centre
~ IL-6 + IL-21

Question 18

Induced T(Reg)

Answer 18

~ regulation + suppression of immune + inflammatory responses
~ IL-2 + TGF-beta

Question 19

Name the two types of memory T-cell.

Answer 19

1) Central memory T-cell = T(CM)

2) Effector memory T-cell = T(EM)

Question 20

Central memory T-cell

Answer 20

~ responds to re-infection via differentiation into T(H) subsets through cytokine influence
~ found in secondary lymphoid tissue

Question 21

Effector memory T-cell

Answer 21

~ already committed to specific lineage

~ found in periphery