B cell activation and regulation Flashcards

1
Q

What is the difference between transmembrane antibodies and MHC molecules on CSM of B cells?

A

The MHC molecules present the antigens processed when the antibody binds to the pathogen.

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2
Q

Where is CD40 present?

A

On the CSM of all APCs

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3
Q

Where are B cells activated?

A

In the lymph nodes

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4
Q

Where are lymph nodes present?

A

Near major organs and tissues

Most likely for a foreign antigen to be picked up by APCs

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5
Q

What differentiates B cells from all other cells in the immune system?

A

Transmembrane antibodies

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6
Q

What is the BCR on B cells composed of?

A

IgM and IgD

BCR is a transmembrane antibody

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7
Q

What happens to naive B cells when they enter lymph nodes?

A

They mature and express IgG and IgD on their surface

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8
Q

What happens to the B cells that leave the lymph nodes without becoming activated?

A

They form short-lived plasma cells that synthesise and release non-specific antibodies like IgM

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9
Q

Where in the lymph nodes are T cells more abundant?

A

Paracortex

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10
Q

Where in the lymph nodes are B cells more abundant?

A

Cortex

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11
Q

What cells cause the initial activation of B cells in the lymph nodes?

A

APCs
T cells
Soluble antigens

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12
Q

Where in the lymph nodes do B cells mature?

A

In the germinal center

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13
Q

What are the two areas of the germinal center called?

A

Dark zone

Light zone

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14
Q

What happens in the dark zone of the germinal center?

A

Clonal expansion

Somatic Hypermutation

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15
Q

What happens in the light zone of the germinal center?

A

Affinity selection
Class switching
Differentiation

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16
Q

What are activated B cells called in the light zone of the germinal center?

A

Centrocytes

17
Q

What are the activated B cells called in the dark zone of the germinal center?

A

Centroblasts

18
Q

What do antibodies do?

A

Activate complement
Enhance phagocytosis
Activate and regulate inflammation

19
Q

Which cells positively selects high affinity B cells in the germinal center?

A

T cells

Follicular dendritic cells

20
Q

What is the germinal center in the spleen called?

A

Primary center

21
Q

Which signals are used to cross-talk between T cells and B cells during their activation?

A

CD40 on B cells and CD40L on T cells
CD28 on T cells and CD80/86 on B cells
Cytokines - IL-4

22
Q

What does the cytokine IL-4 do?

A

Upregulation of certain genes

Upregulate expression of ILR on surface of B cells (IL-receptors)

Triggers somatic hypermutation and increase SA of B cells

Forms immune-synapse

23
Q

What are two B cell disorders?

A

Lymphoma - uncontrolled division of B cells

X-linked hyper-IgM - CD40 deficiency

24
Q

What are possible treatments for B cell disorders?

A

Bone marrow transplant
Antigens neutralising cytokines
Transplant antibodies produced by healthy individual
Prophylactic use of antibiotics and antifungals
Avoid contact with infected people

25
Q

What distinguishes regulatory B cells from other B cells?

A

They only produce IL-10

26
Q

What happens when Bregs recognise T cells with the same antigen?

A

Fears this is an autoantigen

Produces IL-10

Prevents further differentiation of T effector cells

27
Q

What are Natural regulatory T cells and T regulatory-1 cells examples of?

A

T cells that have been induced into their regulatory phenotype by B regulatory cells

28
Q

Why do T and B cells not recognise the same antigen?

A

B cells recognise antigen via antibody that is internalised and processed

The antigen is broken down into peptides and presented on the B cell surface

T cells recognise antigens that are presented by APCs

The epitopes that the T cells recognise are therefore different to the epitopes on the antigens that B cells recognise

29
Q

What is X-linked hyper-IgM syndrome?

A

Genetic mutation in B cells where there is decreased expression of CD40 on their CSM