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Immunology > L3-4 - Antigens, Presentation and Receptors > Flashcards

L3-4 - Antigens, Presentation and Receptors Flashcards

1
Q

What is an antigen?

A

Any molecule that can bind specifically to an antibody or T cell receptor

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2
Q

Define antigenicity

A

The ability of a chemical structure to bind specifically to T or B cell receptors

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3
Q

What is an immunogen?

A

Molecule that elicits an adaptive immune reaction

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4
Q

Define immunogenicity

A

Ability of a molecule to induce a humoral or cell-mediated immune response

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5
Q

What is the difference between antigenicity and immunogenicity?

A

Antigenicity involves ability to bind, immunogenicity involves ability to elicit an immune response

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6
Q

What happens during the innate immune response when there is a local infection?

A

Pathogen enters the body, phagocytes are recruited to kill invaders

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7
Q

What happens during the innate immune response when an infection penetrates tissues?

A

Dendritic cells phagocytise the pathogens, then activate the adaptive immune system

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8
Q

How do antibodies facilitate the removal of extracellular pathogens and toxins?

A

They bind the pathogen/toxin, bind to macrophage, taken in by macrophage and destroyed

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9
Q

What is the main role of the B cell?

A

Processing and presenting antigens

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10
Q

What are the variable domains of an antibody?

A

Regions in the Fab domain that are highly variable and specific for target antigens

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11
Q

What is the name of the antigen binding site of an antibody, and what does this consist of?

A

Complementarity-determining region (CDR) - 3 variable regions of heavy and light chains (6 total) that are paired in an antibody

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12
Q

How is antibody diversity generated?

A

Heavy and light chain genes are rearranged

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13
Q

What are the 5 major antibody isotypes?

A

IgM, IgG, IgE, IgA and IgD

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14
Q

What antibody provides initial response?

A

IgM

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15
Q

What is the major antibody in serum?

A

IgG

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16
Q

What antibody provides the majority of the defence against pathogens?

A

IgG

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17
Q

Which antibody prevents microbial colonisation of mucosal surfaces?

A

IgA

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18
Q

Which antibody aids in the defence against parasites? How does it do this?

A

IgE - triggers mast cells to destroy parasite

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19
Q

What is the constant domain of an antibody, and what is its role?

A

The non-variable part of the antibody that is responsible for activating different effector mechanisms

20
Q

What 2 types of protein chain are antibodies made up of? How many of each are there in IgG?

A

Heavy and light chains

IgG has 2 of each

21
Q

What is the name of the structure within an antigen that the antibody recognises?

A

Epitope

22
Q

What happens within lymph nodes during activation of the adaptive immune system?

A

Dendritic cells migrate here and present processed antigens (from phagocytised pathogens) to T cells

23
Q

What area of an antibody does a T cell receptor (TCR) resemble?

A

Fragment antigen binding (Fab) region

24
Q

What are the names of the protein chains that make up the majority of T cell receptors (TCRs)?

A

Alpha and beta chains

25
Q

What are the 2 main ways a T cell receptor differs from a B cell receptor or antibody?

A

They have 1 antigen binding domain

They are never secreted

26
Q

What type of molecule are CD4 and CD8?

A

Cell surface proteins

27
Q

What is another name for CD4 and CD8 molecules? and how do they get this name?

A

Co-receptors - they associate with T cell receptors to help bind to MHC

28
Q

What cell types are CD4+?

A

Helper T cells and regulatory T cells

29
Q

What MHC class do CD4+ T cells bind to?

A

Class II

30
Q

What are the 3 main types of helper T cell?

A

Th1, Th2 and Th17

31
Q

What is the role of Th1?

A

Co-ordinates inflammatory response against intracellular pathogens

32
Q

What is the role of Th2?

A

Helps B cells produce antibodies against extracellular parasites

33
Q

What is the role of Th17?

A

Protects against extracellular bacteria or fungi

34
Q

What cell types are CD8+?

A

Cytotoxic T cells

35
Q

What MHC class do CD8+ T cells bind to?

A

Class I

36
Q

What are the two groups of protein chains that can make up a T cell receptor? Which is the most common?

A

Alpha and beta chains
Gamma and delta chains

Alpha and beta are most common

37
Q

Where are gamma delta T cells localised?

A

Gut mucosa

38
Q

What 3 receptors are expressed on natural killer cells?

A

Fc receptors
Killer-activating receptors (KAR)
Killer-inhibiting receptors (KIR)

39
Q

Describe how natural killer cell receptors influence the cell’s activation

A

The killer-activating receptors (KAR) bind to common molecules on cell surface. Whether the cell is targeted for destruction depends on the binding of killer inhibiting receptors (KIR) to MHC class I.

If bound - cell is not infected, so is not destroyed
In-bound - cell is infected, destroyed

40
Q

In what organ to T cells mature?

A

Thymus

41
Q

Describe the process of T cell maturation in the thymus

A

Immature T cells are exposed to thymic cells expressing self MHC. Those with a strong affinity are removed, those with a weak affinity survive and enter the peripheral T cell repertoire

42
Q

Which type of T cell has a role in the prevention of autoimmune responses? How does it do this?

A

Regulatory T cells - releases cytokines which inhibit CD4+ Th cells when it encounters MHC class II displaying self antigen

43
Q

What are co-stimulatory molecules in T cell activation?

A

Cell surface proteins present on T cells and antigen presenting cells

44
Q

What is the role of co-stimulatory molecules in CD4+ T cell activation?

A

T cells need 2 signals to activate - bind to MHC class II on antigen presenting cell, binding of co-stimulatory molecule to receptor on T cell

This reduces risk of self responses

45
Q

What are the co-stimulatory molecules / receptors involved in CD4+ T cell activation?

A

CD28 receptor on naïve T cell binds to B7 molecule on antigen presenting cell (APC)

46
Q

What is required for antigen presenting cells to become activated?

A

Binding of antigen to a pattern recognition receptor (PRR)

47
Q

What happens after antigen presenting cells are activated?

A

They upregulate the production of co-stimulatory molecules required for T cell activation and phagocytise the pathogen

Immunology (12 decks)

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