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IMM005 > The humoral response > Flashcards

The humoral response Flashcards

1
Q

What does humoral immunity refer to?

A

The part of the immunity which exists in the cell-free part of the blood, plasma or serum

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2
Q

What is humoral immunity predominantly mediated by?

A

Antibody

Complement

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3
Q

What are the two functions of the humoral immunity?

A

Can directly inactivate a pathogen

Can act indirectly by promoting phagocytosis and cellular recruitment

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4
Q

What is the Fc portion of the antibody?

A

Long part of the heavy chain which is anchored to the cell membrane

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5
Q

What is the function of the Fc portion?

A

Gives the antibody most of the functional capability

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6
Q

What differentiates a mature B cell from a naive B cell?

A

The production and secretion of antibodies

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7
Q

What happens when a B cell is activated?

A

Differentiates into a plasma cell

Settles in the bone marrow

Produces antibodies that mop up the target in the blood

Switches off all genes but those essential for cell survival

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8
Q

How are cell membrane-bound antibodies converted to secreted antigens?

A

The transcription of genes is changed

The constant region has two start sites for transcription:

  • one that codes for the transmembrane form of the antibody
  • one that codes for the secreted form of the antibody

Initially, antibodies will start transcription at the position which includes the exon coding for transmembrane formation

Once the B cell is activated, it starts transcription at a site further along the sequence and forgets the exons that code for the transmembrane part

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9
Q

How are the transmembrane and secreted forms of the antibody different?

A

They are essentially the same molecule

The secreted form is a little shorter since the same molecule is formed lacking the longer sequence making it a transmembrane protein

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10
Q

What is the primary response?

A

The first time a cell is exposed to an antigen

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11
Q

Characteristics of the primary response

A

Slow

Takes between 1 week - 10 days

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12
Q

What is the secondary response?

A

When the same host is exposed with the same antigen

A secondary immune response is formed which is stronger and faster

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13
Q

What is the difference between subunit and live attenuated vaccines?

A

Subunit vaccines need multiple boosts to provide high numbers of circulating antibodies

Infection with the live organism provides the host with long-term immunity

The primary and secondary responses merge into one

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14
Q

What is another name for antibodies?

A

Immunoglobulins

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15
Q

What is the main difference between an immunoglobulin and an antibody?

A

Antibodies do not have transmembrane domains

Immunoglobulins have transmembrane domains

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16
Q

What are the different immunoglobulin isotypes?

A

IgG

IgA

IgM

IgD

IgE

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17
Q

What differentiates the different antibody isotypes?

A

The heavy chains making them up

IgG - gamma heavy chain

IgA - alpha heavy chain

Ect.

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18
Q

What determines the class of antibodies required?

A

The signals the B cell receives

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19
Q

What is the difference between VDJ variations and constant variations?

A

VDJ variations form before B cells become mature

Constant variations form when they are needed

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20
Q

What immunoglobulin is most common in blood?

A

IgG

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21
Q

What immunoglobulin is secreted into the gut, milk or lung spaces?

A

IgA

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22
Q

What immunoglobulin is present on naive B cells?

A

IgM

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23
Q

What is the importance of IgA?

A

Provides protection before the antigen gets into the body

However, deficiency is common and sufferers present with little immunodeficiency

Controversy about its importance

24
Q

What is the function of IgD?

A

Present on naive B cells only

Function is unknown

25
Q

What is the funciton of IgE?

A

Main type mediating common allergies

26
Q

Which immunoglobulins form polymers when secreted?

A

IgA

IgM

27
Q

What type of polymer does IgA make?

A

Dimer

28
Q

What type of polymer foes IgM make?

A

Pentamer

29
Q

Which immunoglobulin is released in high concentration in the primary immune response?

A

IgM

30
Q

Why is IgM released in high concentration in the immune response?

A

It is the immunoglobulin with the highest avidity, since it forms a pentamer structure

So the cumulative strength of bond of the antigen to the whole structure is bigger than in a monomer or dimer

31
Q

What is the difference between affinity and avidity?

A

Affinity explains how tightly a ligand binds to one receptor

Avidity describes the cumulative bonds between the ligand and its receptors on a structure

32
Q

Why does the immune system prioritise on making an immunoglobulin with high avidity instead of high affinity?

A

In the primary immune response, you don’t want to find the antibody which binds most strongly to the antigen, since this takes a long time

Instead, you want to find and make antibodies with relatively low affinity and multiple binding sites to increase the avidity

33
Q

Which antibody is release following secondary exposure to an antigen?

A

IgG

34
Q

Why is IgG released on secondary exposure to an antigen?

A

They expand wuicker

Multivalent antibodies are dangerous since they can lead to blood clots

35
Q

Describe a condition involving the switch between multivalent to single valent antibodies

A

Some rare individuals can’t switch between IgM and IgG

Present with overactive immune systems

36
Q

What 3 ways does an antibody work through?

A

Neutralisation

Direct opsonisation and phagocytosis

Complement activation

37
Q

Which processes do IgG carry out?

A

Neutralisation

Direct opsonisation and phagocytosis

38
Q

Which processes do IgM carry out?

A

Complement activation

39
Q

How do antibodies neutralise toxins?

A

Toxins work through binding to receptors on cells

Antibodies can prevent this from happening by binding to the toxin

A lot of the antibody has to be produced in order to favour the equilibrium where more toxin binds to the antibody than to the receptor

40
Q

What is a disadvantage in the way antibodies neutralise toxins?

A

In order for antibodies to neutralise toxins, there must be antibody present within the time of infection

Therefore, the subject has to have already built immunity to the toxin in order to work

41
Q

Examples of toxins

A

Diphtheria toxin

Tetanus

42
Q

How do antibodies fight viral infection?

A

In order for viruses to work, they bind to cell receptors

Antibodies can block this and stop the virus from infecting the cell

43
Q

What is a disadvantage of how antibodies prevent viral infection?

A

The mechanism won’t work if the subject has not been exposed to the virus, or the virus is already in the cell

44
Q

How do neutrophils and macrophages kill bacteria?

A

Production of toxic agents

45
Q

What is problematic with killing encapsulated bacteria?

A

They can prevent phagocytosis through preventing the phagocyte from fixing onto them

46
Q

How has the body adapted to the resistance of encapsulated bacteria to phagosomes?

A

Antibodies have been developed against the cell wall through adaptive immunity

The antibodies recognise the proteins of the cell wall and coats the bacteria

The phagosome recognises the antibodies

47
Q

How do phagosomes recognise antibodies?

A

Through the Fc portion on antibodies

Fc receptors on macrophages and neutrphils bind to the Fc portion on antibodies

48
Q

What does the Fc and FcR interaction represent?

A

An important example of interaction between the innate and adaptive immunity

49
Q

Describe the function of the different FcR on phagocytes

A

FcRy facilitates uptake and activates phagocytic killing mechanisms

FcRg binds to IgG

FcRe binds to IgE

50
Q

What is the complement system an example of?

A

Part of the innate immunity enhanced by the help of the adaptive immunity

Classical pathway is activated by IgG and IgM

51
Q

Which two Immunoglobulins trigger the classical complement pathway?

A

IgG

IgM

52
Q

Which complement protein do IgG and IgM bind to?

A

C1q

53
Q

Why is serum not a useful tool in conferring passive immunisatio?

A

Contains a lot of different antibodies

Difficult to control

54
Q

What technology allows the formation of monoclonal antibodies?

A

Hybridoma technology

55
Q

What are monoclonal antibodies?

A

Population of one specific antibody specific for an antigen

56
Q

Describe the formation of monoclonal antibodies

A

Mice are injected with antigen you want an antibody against

Spleen is removed

Fuse spleen cells with tumour cells to multiply them

Produce different antibodies

Put one of each B cell extracted in wells to see if you obtained the antibody you want

Harvest the B cell producing the antibody you want, leading to a high concentration of monoclonal antibody production

IMM005 (17 decks)

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