T cellDRRSCD4 CD8LC Flashcards

1
Q

How do Tcells migrate to the thymus?

A

→thymus produce chemokine

→Tcells follow trail of chemokines to thymus

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2
Q

What does the trabeculae divide the thymus into?

A

→lobules

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3
Q

What does the lobule contain?

A

→an outer cortex

→an inner medulla

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4
Q

What is the cortex of the lobule formed from?

A

→dense lymphoid which lacks nodules

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5
Q

Where do immature lymphoid cells enter to proliferate?

A

→cortex

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6
Q

What is the function of epithelial reticular cells?

A

→sequester developing lymphocytes

→form a sheath covering capillaries and lymphatic vessels

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7
Q

What does the sheath in thymus do?

A

→forms what is called the blood-thymus barrier

→prevents antigen contamination of developing and programmed T lymphocytes.

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8
Q

How is the thymus different from lymph nodes?

A

→no lymph sinuses

→ afferent lymphatic vessels

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9
Q

Where is the Hassall corpuscles found in the thymus?

A

→deep in the medulla

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10
Q

What is the Hassall’s corpuscle?

A

→aggregation of mature lymphocytes

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11
Q

When are Tcells mature?

A

→when they express CD4 or CD8

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12
Q

How can Tcell development be chracterised?

A

→flow cytometry

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13
Q

If Tcell progenitors are injected into circulation what do they change into?

A

→Bcells

→NK cells

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14
Q

What do NK Tcells recognise?

A

→CD1 molecule

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15
Q

What are some cells that can be found in the fully developed thymus?

A

→NK Tcells
→gamma delta Tcell
→DN Tcells

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16
Q

What can DN cells be subdivided into?

A

→DN1 and DN4

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17
Q

What molecules are analysed for on CD4 and CD8 molecules?

A

→CD44 and CD25

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18
Q

What type of Tcells appear in foetal thymus before DP cells?

A

→DN cells

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19
Q

At what stage do gamma delta cells become phenotyped?

A

→between DN2 and DN3

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20
Q

What type of Tcells are favoured in early foetal development?

A

→gamma delta

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21
Q

What type of Tcells are favoured in later stages of foetal development?

A

→alpha beta

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22
Q

What do skin gamma delta Tcells express?

A

→Vg5

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23
Q

What do gut gamma delta cells express?

24
Q

What do uterus gamma delta cells express?

25
What restriction do gamma delta cells have?
→not MHC restricted
26
In what way are gamma delta cells similar to antibodies?
→Antigen is recognized directly
27
What roles do gamma delta cells have?
→circulating gamma cells recognize a phospholipid antigen from Mycobacterium tuberculosis →role in cancer surveillance
28
What are the proportions of alpha beta cells and gamma delta cells?
→gamma delta= 10% | →alpha beta = 90%
29
What are the beta and alpha chains analogous to in Ig rearrangement
→beta chain as analogous to the heavy chain →Alpha chain analogous to the light chain
30
Which chain arrangement occurs first?
→beta chain | →begins at DN stage
31
What gene rearrangement occurs at the DN stage?
→D-Jbeta | →V-DJbeta
32
What rearrangement occurs at the DP stage?
→V-Jalpha
33
What does a DP Thymocyte Need to Progress to the SP Stage?
→Functional TCRa chain rearrangement →CD4 and MHC II (To be a CD4+ cell) →CD8, MHC I and TAP (To be a CD8+ cell) →ERK signaling →Calcineurin signaling
34
What interaction lead to thymocyte apoptosis?
→FasL and Fas
35
What molecule inhibits thymocyte apoptosis?
→sFasL and sFas
36
What happens if DP cells bind strongly to CD4 on thymic tissue?
→it will result in downregulation of CD8 mols
37
What happens with low signal intensity to CD4 and CD8 cells?
→death by neglect
38
Where are MHC2 expressed in the thymus?
→expressed on medullary cells | →q-arm of chromosome
39
Which chromosome are MHC complex genes found?
→6
40
Where are MHC molecules found in thymus?
→thymic stromal cells | →low level on APC (DC and macrophages)
41
What is positive selection?
→cell receptor binds to HLA with self antigen
42
Which HLA molecules express MHC1 and MHC2 molecules?
``` →MHC1= HLA A,B,C →MHC2= HLA-DR ```
43
What does positive selection ensure?
→that only T cells are that are useful and can and can engage in recognition are selected
44
What is negative selection?
→exclusion of self-reactive T cells
45
What are the outcomes of negative selection?
→If binding of TCR to antigen is weak then it doesn’t pose danger →If binding is strong then may indicate autoimmunity then reprogrammed for apoptosis
46
What happens with self-reactive cells in negative selection?
→go through further TCR rearrangements (second chance) | →preserves cost
47
How does the thymus represent different antigens from parts of the body?
→transcription activator gene which can induce expression of other tissue specific proteins → AIRE (Autoimmune Regulator) →negative selection
48
Define promiscuous gene expression
→enables generation of self-antigens →Ectopic Gene Expression in the Thymic Medullary Stroma
49
Where do T Regs accumulate?
→Hassall corpuscles and later migrate to different tissues
50
What is the main role of TRegs?
→dampen T cell response
51
What do single positive cells express before they leave the thymus?
→CD25 and Foxp3
52
What is a definitive marker of TRegs?
→Foxp3 →Also expresses CD25
53
When do Tcells become effector Tcells?
→encounter specific antigen, | →they get activated
54
When do Tcells apoptosis in circulation?
→If they don’t find the target
55
At what stage is TCRbeta selected?
→selected with an invariant pTa chain at the DN3 stage
56
At what stage is TCRalpha selected?
→selected with pre-existing TCRb chain at the DP stage
57
What is the result of CD4 or CD8 cell TCR stimulation?
→activation energy