T cell development

Question 1

central tolerance

Answer 1

tolerance to self antigens that is established in lymphocytes developing in central or primary lymphoid organs

mainly achieved by clonal deletion

Question 2

clonal deletion

Answer 2

elimination of immature lymphocytes when they bind to self antigens which produce tolerance of self.

Question 3

chemokine

Answer 3

chemoattractant cytokine that stimulates the migration and activation of cells

Question 4

DiGeorge’s syndrome

Answer 4

failure to develop thymic epithelium. parathyroid glands are absent and there are anomalies in the large blood vessels

Question 5

negative selection

Answer 5

during intrathymic development, thymocytes that recognize self are deleted from the repertoire

Question 6

positive selection

Answer 6

only those developing T cells whose receptors can recognize antigens presented by self MHC molecules can mature in the thymus.

Question 7

signal transduction

Answer 7

general process by which cells perceive changes in their environment.

Question 8

thymic anlage

Answer 8

produces chemotactic factors that attract T cell progenitors

Question 9

CD4-CD8-

Answer 9

double negative, least mature T cells, considerable cell division, undergoes gene rearrangment for TCR beta/gamma/delta, least plentiful, is located in the outer cortex

Question 10

CD4+CD8+

Answer 10

double positive, TCR alpha rearrangement, most plentiful, located in the inner cortex

Question 11

CD4+CD8- or CD4-CD8+

Answer 11

single positive, most are mature cells with high levels of CD3 and TCR beta. There are twice as much CD4 than CD8 in the medulla. Most single positive cells leave the thymus.

Question 12

Single Positive with low CD3 and TCR beta

Answer 12

immature (ISP), transitional cells that are on the way from DN to DP.

Question 13

First Checkpoint (Beta selection)

Answer 13

asseses whether TCR beta chain is functionally rearranged

mediated by pre-TCR, involves RAG, CD3 epsilon, TCR beta, pT alpha.

if you knock out RAG genes, can’t make TCR, blocked at double negative stage

Question 14

Second Checkpoint (positive/negative selection)

Answer 14

assesses whether TCR alpha is functionally rearranged, whether TCR is self MHC restricted, whether the TCR is auto-reactive.

mediated by mature alpha beta TCR. involves TCR alpha, MHC Class 2, beta 2 microglobulin, bare lymphocyte syndrome

knock out TCR alpha, blocked at DP stage, unable to make SP.

Question 15

cells that promote positive selection

Answer 15

cortical epithelial cells

Question 16

cell types that can induce negative selection

Answer 16

thymic DC, cortical epithelial cells, medullary epithelial cells

Question 17

cells that cannot induce negative selection

Answer 17

thymic macrophages

Question 18

Aire transcription factor

Answer 18

AIRE is a transcription factor expressed in the medulla of the thymus and controls the mechanism that prevents the immune system from attacking the body itself