T Cell Development-L6

Question 0

CD4 T cells recognize what MHC molecule?

Answer 0

MHC Class II, B2 domain

Question 1

T cells recognize what?

Answer 1

Peptides derived from self or foreign antigens only when bound to self Major Histocompatibility molecules (MHC)

Question 2

CD8 T cells recognize what MHC molecule?

Answer 2

MHC class I, alpha3 domain

Question 3

Where does T cell development take place?

Answer 3

Thymus

Question 4

Where do TCR gene rearrangements and T cell maturation take place?

Answer 4

Thymus

Question 5

Migration pattern of T cells

Answer 5

Precursors travel from the bone marrow to develop in the thymus. Mature T cells leave the thymus and travel to secondary lymphoid tissues.

Question 6

Prothymocytes

Answer 6

T cell precursors derived from fetal liver and bone marrow

Question 7

Site of prothymocyte entry into the thymus

Answer 7

Cortico-medullary junction via blood vessels

Question 8

Sphingosine-1-phosphate receptors

Answer 8

Control the migration process of thymocytes

Question 9

Surface markers for an uncommitted progenitor cell

Answer 9

CD34 (stem cell surface marker), CD44 (adhesion)

Question 10

Surface markers for a double negative (CD4/CD8) thymocyte committed to the T cell lineage

Answer 10

CD2 (adhesion and signaling), CD5 (adhesion and signaling), IL-7 receptor (cytokine receptor), CD1A (MHC class I like receptor)

TCR genes are beginning the rearrange

Question 11

TCR gene rearrangements

Answer 11

Gamma & delta chains rearrange and form receptor.

B chain gene rearranges and pre-T cell assembles. Expression of CD4 and CD8 are induced.

Question 12

Steps to alpha chain rearrangement of TCR

Answer 12

Two chances for a successful B chain, if obtained then the alpha chain can attempt to rearrange many times until a functional rearrangement is produced. Then the alpha mRNA can be transcribed.

Rearrangement of alpha chain gene always eliminates the linked delta chain locus.

Question 13

Early T cell development summary

Answer 13

Progenitor cells proliferate to double-negative T cells, double negative T cells commit to T lineage, B genes rearrange, immature double positive cells rearrange alpha genes, then mature double positive cells

Question 14

Positive selection of alpha:Beta T cells

Answer 14

• Cortical epithelial cells in the thymus
• If weak or no binding to MHC the thymocyte dies
• If binding is moderate the thymocyte lives
• CD4/CD8 lineage determined by whether binding is with MHC class 1 or 2

Question 15

Negative selection of thymocytes

Answer 15

-If the thymocyte binds MHC too tightly it will die

Question 16

Ligands for positive and negative selection

Answer 16

Self peptide/MHC complexes expressed on stromal and hematopoietic cells

Question 17

AIRE transcription factor

Answer 17

Regulates the expression of some tissue specific antigens in medullary epithelial cells in the thymus (important in negative and positive selection–exposes thymocytes to peripheral tissue specific antigens without leaving the thymus)

Question 18

Avidity model of T cell selection

Answer 18

Depends on the affinity of the TCR-peptide/MHC interaction and the density of the peptide/MHC on the thymic epithelial cell. Determines the total strength of the signal delivered which dictates the outcome. Mechanism by which we get moderately binding thymocytes to MHC.

Question 19

Cell that mediates negative selection of thymocytes

Answer 19

Medullary epithelial cell/dendritic cell

Question 20

Regulatory T cells

Answer 20

Suppress autoreactive T cells by interacting with the same APC