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! Immunology > Day 21 - 13/10/14 > Flashcards

Day 21 - 13/10/14 Flashcards

0
Q

What are Alpha-Beta T Cells called before they recognise their SPECIFIC foreign antigen?

A

Naive

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1
Q

What is the percentage of T-Lymphocytes and alpha-beta-T-Lymphocytes respectively?

A

70% of lymphocytes are T-Lymphocytes

95% of T-Lymphocytes are Alpa-Beta Lymphocytes

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2
Q

What happens when T cells recognise their specific foreign antigen on APCs?

A

1) T Cells undergo cell division called CLONAL EXPANSION

2) Then they DIFFERENTIATE in to EFFECTOR CELLS

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3
Q

What can you say about TCR and BINDING?

A

TCR cannot bind on its own

CO-STIMULATORY molecules

  • allow TCR to bind to APC
  • initiate important signalling
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4
Q

What structure forms at the point of contact between APC and TCR?

A

IMMUNE SYNAPSE

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5
Q

What is the structure of IMMUNE SYNAPSE?

A

1) ADHESION MOLECULES such as LFA-1 , ICAM-1
form a TIGHT RING on the T CELL and APC membranes

2)The TCR and the COSTIMULATORY molecules are held in place at the centre

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6
Q

What can you say about COSTIMULATORY MOLECULES in context of their presence in cells?

A

They are INVARIENT

-do not differ on different cells and are NOT specific

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7
Q

Name major and additional COSTIMULATORY Molecules.

A

CD3
CD4
CD8

CD28
CD80
CD86

Additional
CD40
OX40
ICOS

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8
Q

What does CD3 do?

A

CD3 has long CYTOPLASMIC TAILS which bind and activate TYROSINE KINASES.

This initiates INTRACELLULAR SIGNALLING after specific antigen detection.

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9
Q

What does CD4 do?

A

CD4 binds to CLASS 2 MHC to make the TCR to PEPTIDE-MHC binding better.

CD4 also drags the enzyme: Ick
to CD3.

CD3 can then begins to RECRUIT SIGNALLING ENZYMES
inside the T CELL.

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10
Q

What does CD8 do?

A

Same as CD4, but binds to

CLASS 1 MHC and Ick

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11
Q

What does CD28 do?

A

Binds to CD80 and CD86 on the APC.

This LIGATION triggers signalling which is essential to TRANSCRIBE and make INTERLEUKIN 2 (IL2)

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12
Q

What does IL2 do?

A

IL2 and IL2 RECEPTOR is made by CD4+ cells.
AUTOCRINE interaction between these two result in
CLONAL EXPANSION

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13
Q

What happens if you don’t have COSTIMULATORY MOLECULES?

A

T-Cells become TOLERANT of antigens and is unable to respond to them in the future.

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14
Q

What do CD40ligand, OX40 and ICOS do?

A

After CLONAL EXPANSION, differentiation of the TCELL occurs.

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15
Q

What APC presents antigens in a way that PRIMES NAIVE CD4+ T Cells?

A

Dendritic Cells

16
Q

Dendritic Cells are SENTINELS.

What does this entail?

A

Sample the environment by

  • Endocytosis
  • Pinocytosis
  • phagocytosis
17
Q

What happens when Dendritic Cells find antigens?

A

Dendritic Cells leave the tissue via AFFERENT LYMPHATICS and then enter the T-Cell area of the LYMPH NODES.

There they activate the corresponding CD4+ NAIVE T CELLS

18
Q

How is the Dendritic Cells activated?

A

Dendritic Cell is ACTIVATED by DANGER SIGNALS such as picking up components of Bacteria/Viruses with the TOLL LIKE RECEPTORS (TLR)

19
Q

What do the DANGER SIGNALS do?

A

Increase ANTIGEN PROCESSING

and CCR7 CHEMOKINE RECEPTOR needed to drive Dendritic Cells to the LYMPH NODES

Increase expression COMPLIMENTARY MOLECULES
CD40
CD80
CD86

20
Q

Define Immunological Tolerance

A

A state of antigen specific unresponsiveness to an antigen which
Under other circumstances can stimulate an active immune response.

21
Q

What happens if Tolerance doesn’t work?

A

AUTOIMMUNITY

22
Q

What does Tolerance usually happen to?

A

Food Proteins
Commensal Microbes
Foetus

23
Q

Give examples of Tolerance diseases

A

Coeliac disease - allergic for wheat protein

Crohn’s disease - allergic to commensals

24
Q

What are the two types of tolerance?

A
  • Central
  • Peripheral

(tolerance)

25
Q

What is CENTRAL tolerance?

A

Tolerance against SELF ANTIGENS

Affected Cells- T&B lymphocytes

Affected Organs- THYMUS & BONE MARROW

26
Q

What is PERIPHERAL tolerance?

A

Tolerance against

  • HARMLESS FOREIGN ANTIGENS
  • SPECIFIC SELF ANTIGENS (e.g. During lactation milk/Sex hormones)

Affected Cells - MATURE LYMPHOCYTES
Affected Organs - Secondary Lymphatic organs

27
Q

What are the 4 cellular mechanisms of Tolerance?

A

Ignorance
Clonal Deletion
Clonal Anergy
Active Regulation

28
Q

When does IGNORANCE occur?

A

Lymphocytes which aren’t usually exposed to tissue antigens and so cannot make an immune response.

(Such as lens of the eye/testis)

29
Q

When does CLONAL DELETION occur?

A

When MATURING lymphocytes encounter SELF ANTIGENS in the THYMUS/BONE MARROW.

Self-Reactive T-Cells die.

30
Q

When does CLONAL ANERGY occur?

A

Occurs when MATURE T LYMPHOCYTES
encounter SELF/FOREIGN ANTIGENS
presented by APC
in the ABSENCE of COSTIMULATORY molecules

Can happen in BONE MARROW or
PERIPHERAL IMMUNE SYSTEM

31
Q

When does ACTIVE REGULATION occur?

A

REGULATORY T CELLS
against SELF ANTIGENS in THYMUS
or FOREIGN ANTIGENS in PERIPHERAL NERVOUS SYSTEMS

! Immunology (8 decks)

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