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Defence > T cellDRRSCD4 CD8LC > Flashcards

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?

A

→Vg2

24
Q

What do uterus gamma delta cells express?

A

→Vg6

25
Q

What restriction do gamma delta cells have?

A

→not MHC restricted

26
Q

In what way are gamma delta cells similar to antibodies?

A

→Antigen is recognized directly

27
Q

What roles do gamma delta cells have?

A

→circulating gamma cells recognize a phospholipid antigen from Mycobacterium tuberculosis
→role in cancer surveillance

28
Q

What are the proportions of alpha beta cells and gamma delta cells?

A

→gamma delta= 10%

→alpha beta = 90%

29
Q

What are the beta and alpha chains analogous to in Ig rearrangement

A

→beta chain as analogous to the heavy chain

→Alpha chain analogous to the light chain

30
Q

Which chain arrangement occurs first?

A

→beta chain

→begins at DN stage

31
Q

What gene rearrangement occurs at the DN stage?

A

→D-Jbeta

→V-DJbeta

32
Q

What rearrangement occurs at the DP stage?

A

→V-Jalpha

33
Q

What does a DP Thymocyte Need to Progress to the SP Stage?

A

→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
Q

What interaction lead to thymocyte apoptosis?

A

→FasL and Fas

35
Q

What molecule inhibits thymocyte apoptosis?

A

→sFasL and sFas

36
Q

What happens if DP cells bind strongly to CD4 on thymic tissue?

A

→it will result in downregulation of CD8 mols

37
Q

What happens with low signal intensity to CD4 and CD8 cells?

A

→death by neglect

38
Q

Where are MHC2 expressed in the thymus?

A

→expressed on medullary cells

→q-arm of chromosome

39
Q

Which chromosome are MHC complex genes found?

A

→6

40
Q

Where are MHC molecules found in thymus?

A

→thymic stromal cells

→low level on APC (DC and macrophages)

41
Q

What is positive selection?

A

→cell receptor binds to HLA with self antigen

42
Q

Which HLA molecules express MHC1 and MHC2 molecules?

A 
→MHC1= HLA A,B,C
→MHC2= HLA-DR
43
Q

What does positive selection ensure?

A

→that only T cells are that are useful and can and can engage in recognition are selected

44
Q

What is negative selection?

A

→exclusion of self-reactive T cells

45
Q

What are the outcomes of negative selection?

A

→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
Q

What happens with self-reactive cells in negative selection?

A

→go through further TCR rearrangements (second chance)

→preserves cost

47
Q

How does the thymus represent different antigens from parts of the body?

A

→transcription activator gene which can induce expression of other tissue specific proteins

→ AIRE (Autoimmune Regulator)

→negative selection

48
Q

Define promiscuous gene expression

A

→enables generation of self-antigens

→Ectopic Gene Expression in the Thymic Medullary Stroma

49
Q

Where do T Regs accumulate?

A

→Hassall corpuscles and later migrate to different tissues

50
Q

What is the main role of TRegs?

A

→dampen T cell response

51
Q

What do single positive cells express before they leave the thymus?

A

→CD25 and Foxp3

52
Q

What is a definitive marker of TRegs?

A

→Foxp3

→Also expresses CD25

53
Q

When do Tcells become effector Tcells?

A

→encounter specific antigen,

→they get activated

54
Q

When do Tcells apoptosis in circulation?

A

→If they don’t find the target

55
Q

At what stage is TCRbeta selected?

A

→selected with an invariant pTa chain at the DN3 stage

56
Q

At what stage is TCRalpha selected?

A

→selected with pre-existing TCRb chain at the DP stage

57
Q

What is the result of CD4 or CD8 cell TCR stimulation?

A

→activation energy

Defence (31 decks)

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