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! Immunology > Day 23 - 15/10/14 > Flashcards

Day 23 - 15/10/14 Flashcards

0
Q

Where do T-Cells go after MATURING in the THYMUS?

A

To the THYMUS DEPENDANT AREAS (TDA).
Such as
LYMPH NODES
SPLEEN

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1
Q

How are T-Cells made?

A

PLURIPOTENT, LYMPHOID stem cells develop in the BONE MARROW.

the precursor cells EXIT the BONE MARROW to go to the THYMUS where they undergo POSITIVE and NEGATIVE selection.

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2
Q

How are T-Cells kept alive if they don’t encounter any ANTIGENS?

A

Homeostatic Maintenance

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3
Q

What happens when T-Cells meet corresponding ANTIGENS?

A

They differentiate into EFFECTOR CELLS

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4
Q

If some of the effector cells don’t die for a long time, what are they called?

A

MEMORY CELLS

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5
Q

How does the amount of T Cells relate to an EFFECTIVE immune system?

A

Effective immune system has lots of T CELLS so that it can recognise the maximum number of FOREIGN ANTIGENS

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6
Q

T Cells can only recognise_______type of antigens?

A

Antigens in COMPLEX with SELF-MHC

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7
Q

What type of T Cells account for most immune-responses?

A

Alpha-Beta T Cells

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8
Q

What are T Cells’ Alpha-Beta chains made up of?

A

Constant C - region
Variable V - region
Junctional J - region
Diversity D - region

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9
Q

What is unique to the C,V,J,D regions?

A

C-constant = next to the CELL MEMBRANE and is CONSTANT to all T Cells

V-variable = outer region

J-Junctional _ Link C & V
D-Diverse

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10
Q

Which regions of the T Cell are POLYMORPHIC?

A

V,J,D

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11
Q

Because of the random nature of region selection, there needs to be selection in order that most T-Cells are self-allergen TOLERANT &
MHC Restricted.

What is the SELECTION process called?

A

Positive & Negative Selection - THYMUS

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12
Q

What is the structure of THYMUS?

A

Bilobed organ camposed of LOBULES.
Each LOBULE contains an
OUTER CORTEX and an
INNER MEDULLA

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13
Q

What does the CORTEX contain?

A

The CORTEX contains dividing and dying T LYMPHOCYTES which are enmeshed in a network of
CORTICAL EPITHELIAL CELLS and MESENCHYMAL CELLS (fibroblasts etc.)

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14
Q

What does the MEDULLA contain?

A

The MEDULLA contains MATURE T CELLS and some MEDULLARY EPI|THELIAL CELLS.

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15
Q

What additional cells does the THYMUS contain?

A

MACROPHAGES

16
Q

What happens in the THYMUS?

A

T CELL PRECURSORS enter the THYMUS through the blood vessels in the CORTICO-MEDULLARY JUNCTION from the BONE MARROW.

Then they MIGRATE towards the CORTEX and are INDUCED to DIVIDE under influence of factors made by
CORTICAL EPITHELIAL CELLS and MESENCHYMAL CELLS/

17
Q

In the THYMUS,
POSITIVE SELECTION occurs.
What is this?

A

Only TCR that recognise SELF-PEPTIDES and SELF MHC expressed on CORTICAL EPITHELIAL CELLS are allowed to survive.

18
Q

Why does POSITIVE SELECTION occur?

A

It makes sure that MATURE T CELLS only recognise FOREIGN ANTIGENS when the antigens are TOGETHER with the MHC.

19
Q

How do the other T CELLS die during POSITIVE SELECTION.

A

By APOPTOSIS and are cleared away by MACROPHAGES

20
Q

After positive selection, NEGATIVE SELECTION occurs. What is this?

A

T Cells go towards MEDULLA after positive selection, where if T CELLS react TOO STRONGLY with self peptides+self MHC expressed on DENDRITIC CELLS they are induced to die by APOPTOSIS.

21
Q

What is another name for NEGATIVE SELECTION?

A

CLONAL DELETION

22
Q

What happens to the T Cells that survive positive and negative selection?

A

The T Cells remain in the MEDULLA for a few days, then they migrate to the TDA of secondary lymphoid organs.

23
Q

What does DOUBLE NEGATIVE mean?

A

When entering the CORTEX, the T Cells only express CD3 - they are called DOUBLE NEGATIVE.

24
Q

What does DOUBLE POSITIVE mean and entail?

A

When T Cells Mature, it becomes CD3+CD4+CD8+
-they are called DOUBLE POSITIVE

  • this is when POSITIVE and NEGATIVE selection occur.
25
Q

What does SINGLE POSITIVE mean?

A

After positive and negative selection, the DOUBLE POSITIVE lose a CD4+ OR CD8+ to become SINGLE POSITIVE.

So SINGLE POSITIVE =
CD8+ T Cells (Class 1 MHC) OR
CD4+ T Cells (Class 2 MHC)

26
Q

What are NATURAL REGULATORY T CELLS - Treg

A

T Cells which have an affinity for SELF ANTIGENS, but below the mark for NATURAL SELECTION to take place.

They are selected by MEDULLARY EPITHELIAL CELLS.

27
Q

What does SPECIFIC TRANSCRIPTION FACTOR

FoxP3 used for?

A

FoxP3 can inhibit other immune responses and also

controls Natural Regulatory T Cells - Treg development.

28
Q

What does Treg do?

A

Producea CYTOKINES such as IL10 and TGF(Beta)

29
Q

What causes Treg deficiency and what does that lead to?

A

Lack of FoxP3

AutoImmune Disease - IPEX SYNDROME

30
Q

How do T Cells stay alive?

A
  • HOMEOSTATIC STIMULATION by APC in PERIPHERAL LYMPHOID tissues.
  • CYTOKINE: INTERLEUKIN 7 also helps to keep T Cells alive in the Periphery.

! Immunology (8 decks)

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