L11: T-cell Development

Question 1

DN1

Answer 1

• has c-kit

- high CD44

Question 2

DN2

Answer 2

• γδ or β genes begin rearrangement
• has c-kit
• CD44 decreasing
• CD25 appears
• RAG genes turned on
• CD3 begins

Question 3

DN3

Answer 3

• γδ stop here, β- pre α-receptor
• has c-kit but low
• CD44 is low
• CD25 low
• RAG genes up (but off in γδ)
• CD3 present

Question 4

DN4

Answer 4

• begin α gene rearrangement
• CD44 and c-kit now gone
• CD25 up
• RAG declines
• CD3 present

Question 5

DP

Answer 5

• αβ receptor complete
• CD44, c-kit, and CD25 gone
• RAG rises
• CD4/CD8 now both present
• CD3 present

Question 6

Positive selection

Answer 6

-DP Tcells must bind to an MHC (either I or II) with enough affinity, otherwise they’ll be killed after 3-4 days

Question 7

Negative selection

Answer 7

-DP Tcells bind too well to self-antigen presented on MHC, therefore they are eliminated