t cell development

Question 1

What are the progenitors of T-Cells?

Answer 1

Multipotent stem cells – CD34

Question 2

What is the first T-Cell precursor and what does it exhibit?

Answer 2

a. Committed double negative

b. CD2, CD127 (IL-7R)

Question 3

After a committed double negative what is the next step/ What happens at this
step?

Answer 3

a. Double negative
b. CD4 & CD8 Negative
c. Gene segment rearrangement of beta, delta, gamma

Question 4

Following double negative what is the next step?

Answer 4

a. Double positive (CD4 & CD8 Positive

b. Gene segment rearrangement of alpha

Question 5

What follows this double positive selection?

Answer 5

Negative & Positive selection

Question 6

What then follows double positive & contains what?

Answer 6

a. Single positive

b. TCR & CD4 OR CD8

Question 7

What is positive selection/ MHC restriction?

Answer 7

a. T cell checked if the TCR can work together with the MHC alleles of the
individual

b. Determines either CD4 or CD8 of cell ( If recognizes MHC1 or MHC II)

Question 8

What is negative selection?

Answer 8

a. Checking for self reactivity

b. Using AIRE gene

Question 9

Why are IL-7 and Notch 1 ligand necessary for T-Cell development?

Answer 9

IL-7 and Notch1 Ligand provided by thymic epithelial cells; signals development of thymocytes

Question 10

Somatic recombination in T-Cells proceeds how?

Answer 10

a. Starting with committed double negative progenitor

b. All happen (beta, gamma, and δ ) simultaneously and the first to finish are
combined to form T-Cell Receptor

c. However, it is far more likely that the thymocyte will successfully produce a single productive chain before generating both a and δ chain. Therefore, most thymocytes progress through the α: T-cell pathway.
d. FIRST COME FIRST SERVE

Question 11

How does Beta chain get checked for functionality?

Answer 11

a. Using pTα (First checkpoint)
b. If functional: becomes Double positive (CD4 & CD8)
c. If not functional: Cell can rearrange the gamma/delta genes.
d. If both fail: apoptosis

Question 12

T- Cells that pass negative selection?

Answer 12

Leave thymus as mature T Cells (CD4 OR CD8)

Question 13

Difference between B and gammaδ cells?

Answer 13

a. 2-10% of total T cell pool,
b. Found in high number in mucosal and epithelial regions

**c. Do not undergo selection (negative/positive)

d. Emigrate as CD4CD8 to epithelial tissues in skin, intestines and lungs
e. Immuno surveillance of transformed, damaged or stressed epithelial cells

f. recognize non-peptides, lipids, not completely identified (microbes or
stressed host cells)

g. Does not require APC (MHC+peptide)
h. Limited diversity

Question 14

Difference between BCR & TCR?

Answer 14

TCR do not undergo somatic hypermutation