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Year 1-Immunology-Mubarak > Regulation of lymphocyte responses > Flashcards

Regulation of lymphocyte responses Flashcards

1
Q

Why is regulation of T and B responses important?

A

Unregulated T and B cell responses lead to autoimmunity, allergy and Hypercytokinemia and Sepsis

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2
Q

What can mediate an Allergy?

A

Can be mediated by Antibody (IgE) and mast cells – acute anaphylactic shock

Or by T cells – delayed type hypersensitivity

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3
Q

What is an Allergyic reaction?

A

harmful immune responses to non-infectious antigens that cause tissue damage and disease

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4
Q

What is immunological tolerance?

A

specific unresponsiveness to an antigen that is induced by exposure of lymphocytes to that antigen (tolerogen vs immunogen)

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5
Q

What is a therapeutic potential of immunological tolerance?

A

Therapeutic potential: Inducing tolerance may be exploited to prevent graft rejection, treat autoimmune and allergic diseases

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6
Q

Name two processes for tolerance?

A

Central tolerance

Peripheral tolerance

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7
Q

What is Central Tolerance?

A

Central tolerance – destroy self-reactive T or B cells before they enter the circulation.

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8
Q

What is Peripheral Tolerance?

A

Peripheral tolerance – destroy or control any self reactive T or B cells which do enter the circulation

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9
Q

Where does central tolerance occur?

A

Thymus

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10
Q

What mechanism destroys self reactive T or B cells in Central Tolerance?

A

Positive and negative selection

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11
Q

What happens if an immature B cells in bone marrow encounter antigen in a form which can crosslink their IgM?

A

apoptosis is triggered

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12
Q

How can a T cell developing in the thymus encounter MHC bearing peptides expressed in other parts of the body?

A

A specialised transcription factor allows thymic expression of genes that are expressed in peripheral tissues

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13
Q

How does AIRE promote self tolerance?

A

promotes self tolerance by allowing for the thymic expression of genes from other tissues

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14
Q

What does AIRE stand for and what is it?

A

AutoImmune REgulator

A specialised transcription factor allows thymic expression of genes that are expressed in peripheral tissues

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15
Q

What do mutations in AIRE result in?

A

Mutations in AIRE result in multi-organ autoimmunity (Autoimmune Polyendocrinopathy Syndrome type 1)

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16
Q

Name the mechanisms for Peripheral tolerance?

A

Anergy
Ignorance
Deletion
Regulatiob

RAID

17
Q

What is Anergy in the context of peripheral tolerance?

A

Naive T cells need costimulatory signals in order to become activated

Most cells lack costimulatory proteins and MHC class II

If a naive T cell sees it’s MHC/peptide ligand without appropriate costimulatory protein it becomes anergic – i.e. Less likely to be stimulated in future even if co-stimulation is then present

18
Q

What is ignorance in the context of peripheral tolerance?

A

Antigen may be present in too low a concentration to reach the threshold for T cell receptor triggering

19
Q

Name some immunologically privileged sites?

A

eye, brain

20
Q

What are immunologically privalages sites?

A

Certain sites of the human body have immune privilege, meaning they are able to tolerate the introduction of antigens without eliciting an inflammatory immune response.

21
Q

What is antigen induced cell death?

A

Activation through the T-cell receptor can result in apoptosis

22
Q

What is Regulation in the context of Peripheral Tolerance?

A

A subset of helper T cells known as Treg (T regulatory cells) inhibit other T cells

23
Q

What transcription factor does Treg express?

A

FoxP3

24
Q

What disease is caused by a mutation in FoxP3?

A

IPEX syndrome

25
Q

What is the mechanism of action for regulatory t cells?

A

Secretion of immune suppressive cytokines - IL-10

Inactivation of dendritic cells or responding lymphocytes

26
Q

Why is regulation critical in pregnancy?

A

Pregnancy as a parasitic infection

Exposure to new antigen

Expressed in the context of foreign MHCI

27
Q

What do T Helper cells produce?

A

Cytokines

28
Q

Why is IL-10 A master regulator?

A

Blocks pro-inflammatory cytokine synthesis incl TNF, IL-6, IL-8, IFNγ

Downregulates Macrophages

Viral mimics

Limits the immune response

Produced by Treg

29
Q

Summarise T and B cell collaboration and the mechanisms governing the generation of antibody classes

A

T cells are induced to express the B cell stimulatory molecule CD40 ligand on their cell surface that binds to CD40 on the surface of B cells and secrete cytokines.

T cell derived cytokines drive proliferation and differentiation of B cells into antibody secreting plasma cells

T cell derived cytokines direct the immunoglobin class switching

Year 1-Immunology-Mubarak (8 decks)

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