Exam 1: L12

Question 1

Helper T cells: Th1 produce……

Answer 1

produce inflammatory cytokines ( IFNg, TNFa

Question 2

Helper T cells : Th17 produce…

Answer 2

produce inflammatory cytokines, IL-17

Question 3

Helper T cells : Th2 function

Answer 3

provide helper signals to B cells, Ig class switching

Question 4

Helper T cells : ThF function

Answer 4

provide helper signals to B cells for expansion in lymphoid follicles

Question 5

What is the function of MHC proteins?

Answer 5

• presents an antigen and binds to T cell receptor
  1) antigen is taken up
  2) early endosomes of neutral pH endosomal proteases are inactive
  3) acidification of vesicles activates proteases to degrade antigen into peptide fragments
  4) vesicles containing peptide fuses with vesicles containing NCH II molecules
  5)presents it on the surface of the cell

Question 6

Give an example of MHC co-dominance

Question 7

Describe the concept of having anchor residues on a given MHC binding peptide

Answer 7

• points that possess chemical properties of a certain group like all being aromatic amino acids

Question 8

What is the structure of MHC I and MHC II

Answer 8

MHC I: alpha 1, 2, 3, and beta2 macroglobulin
- alpha 3 interacts with CD8
- peptide binding groove formed by alpha 2 and 1
- 2 to 3 points that serve as anchor residues with similar chemical properties

MHC II- alpha chain and beta chain
- beta 2 is CD4 binding site … interact with each other here
- 4 points for anchor residues with similar chemical properties

Question 9

During what type of situation will you indue MHC molecule expression?

Answer 9

• during infection to increase antigen presentation activities
• gamma IFN can induce MHC class II expression

Question 10

How does MHC I get assembled with intracellular pathogens?

Answer 10

1) endosomes break up the antigen to peptides
2) peptides transported by TAP1 and TAP2 to ER when MHC I are being assembled
3) peptides and MHC I bind via peptide binding cleft to form a complex
4) complex migrate to the cell surface bis Golgi apparatus
5) Will be the ligand of TCR CD8 T cell

• MHC without peptide bound is destroyed

Question 11

How does MHC II get assembled with extracellular pathogens?

Answer 11

1) exogenous antigens are taken in by an acidic vesicle where enzymes digest them into peptides
2)acidic vesicles fuse with another vesicles containing MHC class II
3) MHC Class II molecules are formed with in the ER where 2 chains structures are formed
4) Class II invariant chain (Ii or CD74) is bound to the cleft to prevent self-molecules from binding
5) CD74 is cleaved to leave CLIP in the cleft (before MHC leaves ER)
6) CLIP is replaced by a peptide when the vesicles are fused
7)complex migrate to the cell surface to be presented to CD4 T cell

Question 12

What are superantigens?

Answer 12

• ## bind to the variable region of beta chain of certain TCR ….activating large percentage of T cells