T cell activation

Question 1

when activated, what do CD4 cells do?

-what mhc do they associate with

Answer 1

• stimulate cytokine release

- class 2

Question 2

what do CD 8 cells do when activatied?
what mhc class are they?

Answer 2

• kill infected host cell

- activated by mhc class 1

Question 3

processing

Answer 3

-catabolism of protein to peptides inside a host cell, some peptides bind to MHC molecules

Question 4

presentation

Answer 4

peptide and mhc on surface of host cell interacts with tcr

-either cd4 or cd8

Question 5

exogenous antigens

Answer 5

• pathogens or harmless antigens

- are taken up by specialized host cells, APC

Question 6

endogenous antigens

Answer 6

-come from inside a host cell, generally as a result of infection of the cell

Question 7

exogenous antigen presentation

Answer 7

• via mhc class 2
• antigen taken into acid vesicle and broken into peptides
• peptides associate with newly synthesized mhc class 2 molecules that have their own vesicle
• these will eventually bind to cd4 t cells

Question 8

endogenous antigen presentation

Answer 8

• via mhc class 2
• antigen catabolized in cytoplasm via a proteosome
• peptides transported to ER
• peptides are transported to the eR where they associate with mhc class 1
• eventually mhc will be bound by cd 8
• many endogenous antigens will try to disrupt this process by decreasing expression of mhc class 2

Question 9

what types of cells will be expressing the mhc’s that cd4 and cd8 will associate with

Answer 9

• cd4 cells only interact with the mhc’s of antigen presenting cells, this is because they are the only cells expressing mhc class 2
• cd8 can interacts with mhc’s of any nucleated cell on the body because they all express class 1

Question 10

mhc selectivity to catabolized peptides

Answer 10

• not all peptide fragments that are created when an antigen is internalized will en d up binding to an mhc molecule
• this is because mhc molecules are very specific
• if an mhc never binds a peptide it will never elicit an immune response

Question 11

some hla types are associated with disease, why might this be

Answer 11

-a combination of specific hla types evokes t cell responses that lead to pathology

Question 12

hla types are common amongst…

Answer 12

ethnic groups

Question 13

some hla combinations are helpful

Answer 13

• they can be protective against certain infections such as malaria
• evokes protective t cell responses

Question 14

what two signals are required for t cell activation

Answer 14

• signal 1 via TCR binding with MHC + peptide

- signal 2 from costimulator

Question 15

costimulator pairs

• B7
• CD40

Answer 15

• CD28

- CD40 ligand

Question 16

immature dendritic cells in tissue express

Answer 16

• PRR (TLR)
• phagocytic receptor
• low levels of MHC class 2 and B7
• costimulator molecules

Question 17

mature dendritic cells

Answer 17

• peptide loaded
• activation through TLR signal induces high levels of mhc class 2 and B7, IL-12 and other cytokines and chemokines
• activate cd4, cd8 and many other cells
• migrates out of tissue

Question 18

B 7 is what and binds to what

Answer 18

• it is a costimulator found on dendritic cells

- it associates with cd28 and cd152 (CTLA-4) on t cells

Question 19

what is cd40 and what does it associate with?

Answer 19

• costimulator on dendritic cells

- associates with CD154 (cd40L) on t cells

Question 20

what is cd54 and what does it do?

Answer 20

• it is an adhesion pair on dendritic cell

- binds to cd11a/cd18 on t cell

Question 21

what is cd58 and what does it do

Answer 21

• it is an adhesion pair and is found on dendritic cells

- associates with cd2 on t cells