MIIM - Ocular Defences: The Immune System III - Week 4 Flashcards

1
Q

Is the MHC marker and peptide recognition by a T cell alone enough to activate it?

A

No

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2
Q

Which cell is the best antigen presenting cell?

A

Dendritic cell

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3
Q

In non-inflamed tissue, how efficient are dendritic cells at capturing antigens and stimulating naïve T cells?

A

Highly efficient at capturing antigens but poor stimulators of naïve T cells.

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4
Q

Do dendritic cells have a high or low level of MHCII on their plasma membrane?

A

Low

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5
Q

What is secreted by dendritic cells?

A

TGF-β

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6
Q

Can dendritic cells migrate easily to lymph nodes?

A

No, its restricted

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7
Q

What initiates dendritic cell maturation, and what is it essential for?

A

Initiated when it binds pathogens.
Essential for naïve T cell activation.

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8
Q

Name 6 maturation events for dendritic cells.

A

Migration of the cell to draining lymphoid tissue
Increased antigen processing
Increased MHCI and MHCII expression
Increased surface espression of adhesin
Expression of co-stimulatory molecules
Secretion of cytokines

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9
Q

Do maturing dendritic cells gain or lose capacity to capture antigens?

A

Lose

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10
Q

Name the three molcules involved in the best characterised co-stimulatory signal.

A

CD80 and CD86 on the surface of the APC, and CD28 which is found on all T cells.

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11
Q

Define signal 1.

A

The antigen specific recognition by a T cell

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12
Q

Define signal 2.

A

A co-stimulatory signal needed in addition to signal 1, given by mature dendritic cells.

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13
Q

Define signal 3.

A

Secretion of selected cytokines by the mature antigen presenting cell that has successfully activated and costimulated a naïve T cell.

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14
Q

Once a naïve CD4 T cell receives signals 1 and 2, what does it express (2) and secrete? What else?

A

It expresses CD40L and IL-2R.
It secretes IL-2 and now proliferates.

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15
Q

What happens to a CD4 T cell with signal 3?

A

It differentiates, and performs its effector function.

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16
Q

What does signal 3 facilitate in CD4 T cells?

A

Facilitates differentiation along several possible pathways, each leading to a cell with a particular function.

17
Q

Where do mature APCs interact with CD8 T cells?

A

Secondary lymphoid tissue

18
Q

If a B cell binds an antigen in the lymphoid tissue, can it both release antibodies as well as act as an APC?

A

Yes

19
Q

When a B cell act as an APC, which MHC marker does the antigen end up on?

A

Class II

20
Q

What do activated T cells expressing CD40L do with it? What happens after this (4)? What kind of cell additionally arises from this?

A

It binds B cells that display CD40 and antigen peptides on their MHC.
The B cells proliferate, isotype switch, and undergo affinity maturation, and secrete their antibodies.
Some of these B cells differentiate into memory B cells.

21
Q

Are CD80 and CD86 constitutively expressed on APCs? What about CD40L on T cells?

A

No, none of them are constitutively expressed (only weakly expressed).

22
Q

Define PAMP.

A

Pathogen associated molecular pattern

23
Q

What interaction is a major signal to induce expression of CD80 and CD86?

A

Their interaction with PAMPs

24
Q

Can T cells become activated in the absence of co-stimulation?

A

No

25
Q

Can T cells express CD40L if they are not activated?

A

No

26
Q

Can B cells be fully activated in the absence of CD40 ligation by CD40L?

A

No

27
Q

Once CD4 T cells are activated and migrated to the infection site, what two things do they do there?

A

Activate tissue macrophages
Activate other cell types such as fibroblasts, neutrophils, and keratinocytes.

28
Q

What molecule do cytotoxic T cells use to kill infected cells?

A

Perforin

29
Q

Name three ways T cell activation can be inhibited, and give one example for each.

A

Immunosuppressive drugs - inhibiting IL-2 production
Antibodies - block T and APC/T and B cell interactions
Soluble ligands - block co-stimulatory interactions

30
Q

Describe briefly how the innate and adaptive immune systems activate each other (5).

A

Innate activates adaptive by increasing co-stimulation via APC action and producing cytokines inducing T cell differentiation.
Adaptive activates innate by producing antibodies that act as opsonins triggering phagocytosis and complement cascades, and producing cytokines recruiting macrophages and other phagocytes.

31
Q

Name the cytokine responsible for upregulating the production of the following antibodies:
IgA
IgG
IgE

A

IgA - TGFβ
IgG - IFNγ
IgE - IL-4