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1. Immunology > The Adaptive Immune System > Flashcards

The Adaptive Immune System Flashcards

1
Q

What are the three main features of the adaptive immune system?

A

It responds to a specific pathogen

It has a ‘memory’ of specific antigens

It improves upon re-exposure

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2
Q

What is an antigen?

A

A molecule that provokes an immune response

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3
Q

What does the adaptive system require to become activated?

A

It requires the innate system

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4
Q

What are the cells of the adaptive immune system?

A

Lymphocytes

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5
Q

What are the two different types of lymphocytes?

A

B and T

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6
Q

How does the adaptive system response differ upon re-exposure?

A

It will be more rapid and more intense

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7
Q

Where do both types of lymphocytes originate from?

A

From progenitors in the bone marrow

Their precursor cell is the common lymphoid precursor

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8
Q

Where do B-cells mature?

A

In the bone marrow

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9
Q

Where do T-cells mature?

A

In the thymus

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10
Q

What does maturing mean in terms of lymphocytes?

2

A

Forming of a receptor

Gaining the ability to recognise and respond to specific antigens

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11
Q

What are cells called before they have matured?

A

Immature

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12
Q

What percentage of cells that go to the thymus die?

A

98%

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13
Q

What is it called when cells audition to become T cells?

A

T-cell education

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14
Q

What happens if a cell fails to become a T cell?

A

It is killed

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15
Q

What happens if a cell succeeds in becoming a T cell?

A

It enters the medulla

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16
Q

How many copies of its receptor does each lymphocyte have?

A

about 104 to 106 receptors

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17
Q

What is the receptor on a T cell called?

A

a T-cell receptor

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18
Q

What is the receptor on a B cell called?

A

a B cell receptor

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19
Q

What is present as the receptor on B cell?

A

antibodies

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20
Q

What are the two types of T cells?

A

Killer T cells

Helper T cells

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21
Q

What is the ratio between helper T cells and killer T cell?

A

You have twice as many helpers as you do killers

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22
Q

How are T cell receptors made?

A

They are made by a totally random process of gene shuffling

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23
Q

How do B cell receptors work?

2

A

The antibody molecule can be reproduced many times

These antibodies can be released from the cell at a distance

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24
Q

What are lymphocytes called after they have gotten their receptors?

A

Naive cells

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25
What happens to lymphocytes once they have become naive cells?
They travel to the lymph nodes, spleen or other lymphoid organs to await activation
26
Describe the structure of the T-cell receptor. | 4
Made of 2 polypeptide chains Usually an alpha and a beta chain Rarely a gamma and theta chain Has variable regions that dictate what it will bind to
27
Describe the structure of an antibody.
Made of 4 protein chains
28
What type of cell secretes antibodies?
Plasma cells
29
What is the process by which clonal lymphocytes form?
Clonal expansion
30
What is clonal expansion?
The process by which a lymphocyte with the correct receptor replicates to form clonal lymphocytes
31
How do T cells become activated?
T cells need antigen presenting cells to show them their target
32
Name the three antigen presenting cells.
Dendritic cells Macrophages/monocytes B-cells
33
How does antigen presentation work? | 4
The antigen presenting cells phagocytose pathogens The pathogens are killed and chopped up into peptides The antigen presenting cell display peptide fragments of the pathogens on their surfaces The antigen presenting cell then approaches the T cells and if its receptor binds to the peptide the T cell will become activated
34
What does MHC stand for?
Major Histocompatibility Complex
35
Why do T cells need MHC molecules?
antigen presenting cells need to present their pathogen's peptide in an MHC molecule to the T cells
36
Why are T cells known as MHC restricted cells?
Because T cells can only recognise antigens in the context of MHC
37
Where does antigen presentation and T-cell activation usually occur?
In peripheral lymphoid organs such as lymph nodes
38
What happens when an APC takes up a pathogem?
It becomes activated and migrates to a regional lymph node
39
What is the main function of lymph nodes?
They act as organising centres for immune responses
40
How does an APC know it has made contact with a pathogen? | 3
APCs have pattern recognition receptors on their surface These are called Toll Like Receptors (TLRs) TLRs recognise specific pathogen associated molecular structures (PAMS)
41
What are the receptors on APCs called?
Toll Like Receptors
42
What does PAMS stand for?
Pathogen associated molecular structures (PAMS)
43
What does TLR stand for?
Toll like receptors
44
Give some examples of PAMS.
LPS Double stranded RNA Flagellin
45
What happens to an antigen presenting cell when a toll like receptor is activated? (2)
The APC becomes activated This allows it to migrate to a lymph node and interact with T cells
46
Is antigen presentation needed for memory cells?
Yes
47
What are killer cells also called?
Cytotoxic cells
48
What do killer T cells do? | 3
They kill virus infected cells They kill tumour cells Apoptosis
49
What do helper T cells do? | 2
They secrete cytokines to react with other cells They help B cells make antibodies
50
What CD molecules are always expressed by T cells?
CD3
51
What CD molecules are always expressed by helper T cells?
CD4
52
What CD molecules are always expressed by killer T cells?
CD8
53
What type of cell is needed to activate a killer T cell?
Any nucleated cell MHC class 1
54
What type of cell is needed to activate a helper T cell?
APC MHC class 2
55
What is an epitope?
A specific amino acid sequence from an antigen
56
Can B cells activate without T cell help?
Yes But their function is limited
57
How exactly does a B cell activate without the help of a T cell? (5)
If more than one antibody reacts with the epitopes on an antigen they will become cross linked This cross linking activates the B cell B cell then becomes a plasma cells Plasma cell can now secrete antibodies However, it will only make IgM antibodies (1/5 types)
58
Explain how a helper T cell activates a B cell | 4
A B cell has a peptide (its an APC) and its trying to find a T cell If a Helper T cell recognise the peptide it can provide cytokines to the B cell These cytokines help the B cell make antibodies This also allows memory B cells to be made
59
What are antibodies? | 2
Soluble versions of the B cell receptor Immune proteins synthesized and released by plasma cells
60
What are antibodies also called? | 2
Gamma globulins Immunoglobulins (Igs)
61
Describe the structure of an antibody. | 4
4 protein chains - 2 identical light chains and 2 identical heavy chains Chains held together by disulphide bridges 2 regions - fab region (fragment with antigen binding) and the Fc region (fragment that is crystallisable) Two binding sites for antigens
62
What are the two regions in an antibody?
Fab region Fc region
63
What is the fab region of an antibody?
Fragment with antigen binding
64
What is the Fc region of an antibody?
Fragment that is crystallisable
65
How many different types of antibodies are there?
Five
66
What are the five different types of antibodies?
IgM IgA IgD IgG IgE
67
What does each variable region of an antibody contain?
An antigen-binding site
68
What are the four main ways antibodies deal with antigens?
Precipitation/agglutination Lysis Neutralization Opsonisation
69
Explain precipitation
Occurs when antibodies bind their soluble targets into clumps
70
Explain agglutination.
Occurs when antibodies cause clumping of insoluble particles Something insoluble is bound up by antibodies
71
What is the function of precipitation/aglutination?
This sequesters the target and increases the likelihood of phagocytosis Something soluble is bound up by antibodies
72
Explain how antibodies use lysis. | 5
Antibodies bind to a bacterium The complement system is activated Complement proteins form a MAC This perforates the bacterial cell membrane Cell lyses
73
Explain how antibodies are involved in neutralisation of antigens. (3)
Antibodies bind to their target and interfere with the pathogen function Antibody interferes with viral entry into host cell Antibody binds to toxins and renders them inactive
74
How are antibodies involved in opsonisation? | 2
Antibodies bind to pathogens This marks out pathogens for phagocytes
75
How long is the lag period after the initial encounter until antibody production?
It takes 5-7 days
76
What happens ten days after an initial encounter?
Plasma antibody levels peak and begin to decline
77
How is the memory response greater than the initial response? (4)
A shorter lag time- Plasma cells that last longer- Higher Antibody levels achieved more quickly- Higher efficiency of binding between Antigens & Antibodies

1. Immunology (9 decks)

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