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PA20351 > T cells > Flashcards

T cells Flashcards

1
Q

What are T cells?

A

They are thymus selected lymphocytes that mature in the thymus. They are generated in the bone marrow but migrate and mature here.

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2
Q

What are T cells required for?

A

Cell mediated immunity. They evoke responses by mobilising and activating other cell types or attaching to and recognising and killing virally infected cells. They help B cells become activated and produce antibodies.

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3
Q

What do T cells respond to?

A

Antigenic fragments that are presented by MHC molecules on APCs.

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4
Q

In terms of recognising foreign material, how do B cells and T cells differ?

A

T cells can only recognise antigenic fragments - the antigen needs to be broken up.

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5
Q

What are the different types of T cells?

A

T Helper cells (1 and 2) and cytotoxic T cells.

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6
Q

What is the main physical characteristic of T helper cells?

A

They contain CD4 surface protein. This has a physiological function but is generally used as a marker.

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7
Q

What cell surface receptor do all T cells have?

A

CD3.

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8
Q

What is CD25?

A

The interleukin receptor which is a growth factor for T cells. If T cells have CD25, they are active T cells.

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9
Q

What is the function of Th1 cells and what do they produce?

A

Activate macrophages and cytotoxic T cells and produce large amounts of IFNgamma/TNFalpha.

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10
Q

What is the function of Th2 cells and what do they produce?

A

They provide costimulatory help to B cells and secrete IL-4/5/10 to stimulate these B cells.

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11
Q

What is the main anti-inflammatory cytokine?

A

IL-10.

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12
Q

What causes chronic inflammation?

A

Overactivation of the B cells.

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13
Q

What are methods to treat chronic inflammation?

A

B cell therapies - targeting the B cells in chronic inflammation.

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14
Q

What cell surface receptor do cytotoxic T cells have?

A

CD8+.

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15
Q

What is the function of cytotoxic T cells?

A

They recognise antigenic fragments presented on class I MHC and kill infected cells.

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16
Q

What are the 4 types of antigen presenting cell?

A

Macrophages, neutrophils, B cells and dendritic cells.

17
Q

What surface proteins are found on T regulatory cells?

A

CD4, CD2 - only expressed on activated T cells.

18
Q

How are T regulatory cells linked to T helper cells?

A

They are a subpopulation of active T helper cells, but instead of stimulating the immune response they dampen it down.

19
Q

What is one of the key functions of T regulatory cells?

A

They suppress the activation of self-reactive T cells to stop us reacting to our own tissue.

20
Q

What is Foxp3?

A

A transcription factor that is critical for immunosuppressive function. Mutation can lead to autoimmunity.

21
Q

What cytokines do T regulatory cells secrete?

A

Anti-inflammatory cytokines such as IL-10. TGFbeta.

22
Q

What structure does the T cell receptor have similarities with?

A

Antibodies.

23
Q

What is the structure of the T cell receptor?

A

It is made up of alpha and beta membrane bound chains with immunoglobulin domains.

24
Q

What is the T cell receptor associated with in the membrane?

A

CD3 chain.

25
Q

What is the process of self tolerance?

A

Undergoing selection to remove T cells that are reactive to self antigens, but keep cells that have an ability to recognise and interact with MHC molecules - MHC molecules contain self antigen. It is positive and negative selection.

26
Q

Does somatic hypermutation occur in T cells?

A

No - the affinity of the receptor will always be quite low.

27
Q

What do the T cell receptors associate with?

A

CD3 chains - the signalling molecules associate with these and get activated. It associates non-covalently.

28
Q

What is the human leucocyte antigen system?

A

It is a gene complex encoding the MHC proteins in humans.

29
Q

What are the alleles of MHC I?

A

HLA 1, 2 and 3.

30
Q

What are the alleles of MHC II?

A

HLA DP, DQ, DR.

31
Q

What are MHC I recognise by?

A

CD8 T cells.

32
Q

What are MHC II recognised by?

A

CD4 T cells.

33
Q

Where does the peptide sit in the MHC?

A

In the groove of the MHC.

34
Q

How do class I and II MHC compare?

A

Class II is a bit bigger/wider and can encompass more.

35
Q

What does T cell recognition require?

A

Endocytosis, processing and presentation by APC in conjunction with the MHC molecule.

36
Q

Where does the TCR bind?

A

Across both the peptide and MHC residues.

PA20351 (11 decks)

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