T cell differentiation

Question 1

TCR

Answer 1

t cell receptor
-contains alpha/beta or gama/sigma

• both chains contain a V and C domain
• chains connected by disulfide bonds
• there are different chains (sigma and gama) found on a minor population of T cells
• antigen binding occurs in the V (variable) region

Question 2

antigens on all T cells

Answer 2

• TCR (could be alpha/beta or gama/sigma)

- CD3

Question 3

alpha/beta TCR T cells differentiate into what?

Answer 3

CD4 and CD8 T cells

-these CD’s represent coreceptors

Question 4

what do T cells respond to?

Answer 4

• protein antigens (on pathogens) the get INTO host cells via infection or uptake
• respond mainly to peptides
• whereas antibodies on b cells interact with antigens of ALL chemical composition FLOATING in the blood/bodily fluid

Question 5

T cells interact with

Answer 5

-peptides bound within the grooves of MHC on surface of host cell

Question 6

MHC expression

Answer 6

• class one: all nucleated cells (ie not RBC’s)

- class two: expressed constitutively only on APC’s (DC, B, and macrophages, thymic non-lymphoid cells)

Question 7

how do MHC class 1 and 2 molecules interact with T cells

Answer 7

• class 1: interacts with CD8 on CD8+ cells

- class 2: interacts with CD4 on CD4+ cells

Question 8

what happens when a CD4 is bound by an MHC class 2

Answer 8

-cytokines are released

Question 9

what happens when a CD8 interacts with an MHC class 1

Answer 9

-killing of infected host cell

Question 10

why do we have CD8 and CD4 on different cells?

Answer 10

-they bind to different MHC molecules and therefore we can create different immune responses based upon the cell type infected and the antigen present

Question 11

once the CD’s are bound by their respective MHC, what happens molecularly

Answer 11

-they enhace the signal through the TCR

Question 12

T cell development overview

Answer 12

• lymphoid progenitor made in the BM
• transported to the thymus
• double negative
• double positive alpha/beta CD4/CD8
• positive selection
• single positive CD4 or CD8
• negative selection
• mature CD4+ and CD8+ released into periphery

Question 13

what happens in the double negative thymocyte?

Answer 13

-TCR genes start to rearrange

Question 14

what else can be made by the common lymphoid progenitor in the thymus

Answer 14

-NK cell

Question 15

double negative thymocyte differentiates into

Answer 15

• either gama/sigma CD3 or

- alpha/beta (CD3) without CD4 or 8(these move on to selection)

Question 16

Double positive cells

Answer 16

• alpha/beta that have both CD 4 and 8
• if these interact with thymic epithelial cells then they curvive and choose either a CD4 or CD8 lineage
• CD4 is more abundant and therefor more commonly chosen

Question 17

T cells that have survived positive selection go on to

Answer 17

• negative selection
• thymic dendritic and medullary epithelial cells, expressing MHC 1 and 2 interact with positively selected T cells
• if these cells interact with the dendritic cells, they undergo apoptosis (this shows too high of an affinity for self)
• if they do not interact, they survive

Question 18

what composes the TCR complex?

Answer 18

• TCR
• CD3
• zeta

Question 19

what is zeta

Answer 19

• signal transduction molecues associated with the TCR

- these are membrane spanning proteins