T Cells

Question 1

MHC I Features

Answer 1

Intracellular pathogens
expressed on all nucleated cells
alpha chain 45kD in three distinct domains
B2 microglobulin 12kD

Question 2

MHC II Features

Answer 2

Extracellular pathogens
APCs only
alpha chain 33kD
beta chain 28kD

Question 3

T Cell Receptor

Answer 3

alpha chain has VJ, beta chain has VDJ and variable region, arranged in some way as immunoglobulins

Question 4

Factors contributing to TCR/Ig Diversity (5)

Answer 4

1. multiple copies of VJD
2. D region can be transcribed in different reading frames
3. imprecise joining may occur during rearrangements of genes
4. nucleotides may be randomly inserted/deleted
5. any alpha chain may join with any beta chain

Question 5

Medawar and Burnet - 1960 Nobel Prize

Answer 5

Demonstrated acquired immune tolerance - non-identical cattle twins happily carried additional set of red blood cells from their sibling - acquired through shared placenta in the wommb - gradual learning process through embryonic life

Question 6

Th2 production

Answer 6

IL-4 –> STAT6 –> GATA3 –> Th2

Question 7

Th1 production

Answer 7

IL-12 –> STAT4 –>T-bet –> Th1

Question 8

Th17 production

Answer 8

IL-6/IL-23–> STAT3 –> Ror gammat T –> Th17

Question 9

Treg production

Answer 9

TGF-beta –> STAT5 –> Foxp3 –> Treg

Question 10

Functions of CD4+ (2)

Answer 10

1. maturation of B cells into plasma cells and memory B cells
2. activation of cytotoxic cells nad macrophages - release of different types of cytokines to facilitate different types of immune responses

Question 11

Activation of T cell steps (3)

Answer 11

Signal 1: TCR binds to antigen as it is held in the MHC complex on the surface of the APC (stabilised by binding of CD4/8 to MHC)
Signal 2: CD28 (T cell) binds to CD80/86 (B7.1/2) on APC
Signal 3: differentiation controlled by different cytokine release

ALSO PRIMING - cell-cell interactions - transient - hold cells together - LFA-1 on T cell to ICAM-1 on APC

Question 12

Th 1 cells effector cytokines and functions (3) (generally proinflammatory)

Answer 12

1. IFN-gamma - activates macrophages and B cells
2. IL-2 - stimulates B cell growth
3. TNF-beta - activates macrophages and neutrophils

Question 13

Th2 cells effector cytokines and functions (3)

Answer 13

1. IL-4 - B cell activation, inhibition of macrophage activation
2. IL-5 - eosinophil growth and proliferation
3. IL-10 - inhibits Th1, inhibits macrophage cytokine release

Question 14

CD8+ activation(2)

Answer 14

1. Simple activation - interaction with proffesional APC
2. long lasting memory cell production - CD8 t cells primed in the presence of CD4 cells undergo second round of clonal expansion - occurs via CD40L (T CELL) and CD40 on APC-DC cell (licensing) - then activates CD8 T cell

Question 15

methods of killing by CTL (2)

Answer 15

Fas/FasL interaction

Cytotoxic proteins inside granules (perforin and granzyme)