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Unit 3 Micro and Immunology > T Cell Development > Flashcards

T Cell Development Flashcards

1
Q

Where does T cell development take place?

A

Thymus

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2
Q

What are the phases of T cell development that take place in the thymus?

A

Maturation
Cell proliferation
TCR gene rearrangements
Cell apoptosis

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3
Q

What are the two methods of T cell selection?

A

Positive and negative

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4
Q

What is DeGeorge’s syndrome?

A

Chromosomal disorder leading to decreased T cells

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5
Q

What pharyngeal pouches does the thymus come from?

A

3rd pair

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6
Q

What are the pouches made out of?

A

endoderm

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7
Q

What are the clefts made out of?

A

exoderm

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8
Q

What forms the capsule around the thymus?

A

Mesenchyme

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9
Q

What is the cellular organization of the thymus?

A

1- subcapsular region
2- cortex
3- corticomedullary junction
4- medulla

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10
Q

Where are hassall’s corpuscles located?

A

in the medulla of the thymus

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11
Q

Is the cortex or the medulla more dense?

A

the cortex

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12
Q

What type of cells travel to the thymus?

A

T cell precursors (prothyrocytes)

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13
Q

Where do prothyrocytes come from?

A

Fetal lever and bone marrow

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14
Q

Where do prothyrocytes enter the thymus?

A

at the cortico-meduallary junction

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15
Q

How do the prothyrocytes enter the thymus?

A

blood vessels

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16
Q

What signals are used to get the prothyrocytes to the thymus?

A

chemotactic substances control prothyrocyte travel

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17
Q

What are the most immature T cells? What do they express?

A

The least mature are double negative t cells that have just migrated from the bone marrow

18
Q

Do double negative’s express the TCR?

A

Some do, but about 2/4 are triple negative

19
Q

What type of somatic rearrangement occurs at the DN stage?

A

gamma, beta and delta. NOT alpha

20
Q

What does gamma pair with? What does alpha pair with?

A

gamma pairs with delta and alpha pairs with beta

21
Q

What are double positive T cells?

A

express both CD4 and CD8

22
Q

when does alpha somatic rearrangment occur?

A

at the DP stage

23
Q

When does the most apoptosis of T cells occur?

A

At the DP stage because dp’s are bery sensitive to anything that can cause apoptosis

24
Q

What are single positives?

A

DP’s that have down regulated one of the two co-receptors

25
Q

Which is more prevalent, CD4+ or CD8+?

A

CD4+

26
Q

What gets turned on first, CD4 or CD8?

A

CD4

27
Q

What is it easier to become? AB or DG?

A

Alpha beta

28
Q

A precursor cell that comes to the thymus is destined to become what?

A

dendritic cell, B cell or T cell. The cell needs to chhose the T cell lineage

29
Q

SInce beta and alpha rearrangements occur at different times, what does beta pair with?

A

a surrogate alpha chain so some rounds of proliferation can occur before teh alpha chain is rearranged

30
Q

Where does DP selection happen?

A

inner corted

31
Q

When a cell has committed to either CD4 or CD8 where does it go within the thymus?

A

The medulla

32
Q

What is the first T cell checkpoint?

A

Beta selection. It is to assess whether TCR beta is functionally rearranged

33
Q

If a cell passes beta selection, what proceeds?

A

Proliferation and expression of CD4 and CD8 and termination of TCR gamma expression. Alpha rearrangement begins as well

34
Q

What is the second T cell checkpoint?

A

positive and negative selection

35
Q

what is the purpose of the second t cell checkpoint?

A

1- assess whether TCR alpha is functional
2- assess whether TCR is self MHC restricted
3- assess whetherTCR is auto-reactive

36
Q

If there is no reaction with the peptide/ MHC?

A

The cell dies by neglect

37
Q

What is positive selection?

A

The cell needs to bind MHC and self peptide just enough. I it binds too much or too little is will die via apoptosis

38
Q

What causes peripheral ligands to be expressed in the medullary epithelial cells?

A

Aire transcription factos

39
Q

What cells mediate positive selection?

A

cortical epithelial cells

40
Q

What cells mediate negative selection?

A

any cell can mediate it

Unit 3 Micro and Immunology (25 decks)

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