T cells: Development, activation and immunity

Question 1

Knockout mice lacking MHC class II molecules

Answer 1

fail to produce mature CD4+thymocytes, or those clacking MHC class I molecules fail to produce mature CD8+ thymocytes, because at some level lineage commitment requires engagement between the MHC and the appropriate CD4/8 receptor.

Question 2

β-Selection initiates

Answer 2

maturation to the DN4 stage, proliferation, allelic exclusion, maturation to the DP stage, and TCR α-chain locus rearrangement

Question 3

Negative selection of tissue-specific antigens occurs

Answer 3

only in the medulla of the thymus, by medullary thymic epithelial cells (mTECs) and some DCs that pick-up antigens produced by mTECs.

Question 4

Most thymocytes (>90%)

Answer 4

die of neglect in the thymus because they either did not produce viable TCR, or because they do not bind to self MHC.

Question 5

Thymocyte precursors express neither

Answer 5

CD4 nor CD8 and enter the thymus from the bone marrow at the corticomedullary junction.

Question 6

Thymocytes that bind peptide-MHC complexes with

Answer 6

high affinity are negatively selected.

Question 7

Double-negative (DN) thymocytes progress through

Answer 7

several stages distinguished by expression primarily of CD44 and CD25.

Question 8

Some thymocytes with autoreactive T-cell receptors

Answer 8

mature to become TREG cells.

Question 9

Regulatory T cells help maintain

Answer 9

peripheral tolerance

Question 10

Commitment to the CD4+ T-cell lineage is regulated by

Answer 10

Th-Pok

Question 11

Runx3 regulates

Answer 11

commitment to the CD8+ lineage

Question 12

Precursors of thymocytes enter the thymus at

Answer 12

the corticomedullary junction