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MIIM30002 - Principles of Immunology > Lecture 4 - Antibody - Antigen interactions > Flashcards

Lecture 4 - Antibody - Antigen interactions Flashcards

1
Q

What is the difference between an antigen and an immunogen?

Give examples of each

A

Immungen: a substance that elicits an immune response
Antigen: target of the immune response

For example:
Immunogen:
• Influenza virion
• Hapten carrier complex

Antigen:
• NA (neuraminadase)
• Hapten
• HA (haemagglutinin)

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2
Q

What is the determinant?

A

AKA Epitope

The area on the antigen to which the Ab binds

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3
Q

What is Ab?

A

Antibody, aka immunoglobulin

Molecules made by B cells that bind to antigen

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4
Q

Describe generic variability of Ag.

What about the immunogen?

A

Antigen can be:
simple: moiety
or complex: protein structure

The immunogen is nearly always complex

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5
Q

What are haptens?

A
  • Small organic moiety found on polypeptides

* target of an Ab response

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6
Q

What is the hapten carrier complex?

A
  • A polypeptide / protein (containing the hapten moiety)

* required for the adaptive immune responsex

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7
Q

Why is the hapten-carrier complex required for the adaptive immune response?

A
  • It is the minimum size required for cross linking on surface B cell receptors
  • It contains T cell determinants
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8
Q

Describe binding of the hapten to the carrier molecule

A

Must be covalently bonded in order to generate an adaptive immune response

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9
Q

Draw a schematic of Ab

A

Slide 9

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10
Q

What types of molecules can antibodies recognise?

A

All manner of chemicals:
• protein
• peptide
• haptens

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11
Q

Describe Ab recognition of Ag

A

Dependent on Complementation of the antigen to the Ag recognition site on the Ab

The recognition site on Ab is very specific for Ag

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12
Q

What is the ‘footprint’

A

Another name for the Determinant, or Epitope on an Antigen

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13
Q

Describe Complementation in protein Ag

A

The recognition site on the Ab is specific for the side chains of the determinant.
Single amino acid changes can result in failure of complementation

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14
Q

What types of interactions happen between Ag and Ab?

A
  • Electrostatic bond
  • Van der Waals
  • Hydrogen bonding
  • Hydrophobic force
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15
Q

What are the two types of protein determinants?

A

Linear

Conformational (discontinuous)

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16
Q

Describe the effect of denaturation on the two types of protein determinants

A

Linear: no effect
Conformational: conformation is lost, no Ab-Ag binding

17
Q

Describe some instances of an immunogen having more than one antigen

A
  1. Influenza:
    • HA
    • NA
  2. Hapten-carrier molecule
    • anti-hapten antibody
    • anti-carrier antibody
    • anti-hapten+carrier antibody
18
Q

What is serum / antiserum?

What does it contain?

A

Blood depleted of erythrocytes from an immune individual

• contains multiple specificities of antibodies

19
Q

What does the antiserum of an individual immune to a given strain of influenza contain?

A
  • anti-HA antibodies

* anti-NA antibodies

20
Q

Describe cross-reactivity

A

Ab bind to various protein molecules

This comes about because the specific determinant is conserved between various protein molecules

21
Q

Describe cross-reactivity of flu strains

A

Influenza virions have many determinants.
Every flu season, the determinants change
From year to year however, there may be cross over of the determinants present on the virion

22
Q

What is antigenic drift?

A

Gradual change of viral antigenic determinant through mutation

23
Q

What is serology?

A

Use of antibodies to determine structural relatedness of antigens
For example, adding Ab to various strains of virus to determine the presence of the same antigens in the various strains

24
Q

Compare Antibody and T cell epitopes

A

T cell epitopes are always linear, whereas epitopes that Ig recognises can be linear or conformational

25
Q

What is an example of a hapten?

A

DNP: dinitrophenyl

26
Q

Describe the response when a single hapten molecule binds to a B cell receptor

A

This is not a strong enough stimulus to elicit a response

27
Q

How many B cell receptors need to be engaged in cross linking for a response to be elicited?

A

Around 20

28
Q

What is the other name for discontinuous antigen determinants?

A

Conformational

29
Q

Are haptens immunogenic?

A

No

They must be covalently linked to a hapten carrier

30
Q

What are van der Waals forces?

A

Weak interaction between atoms

31
Q

What are hydrogen bonds?

A

Weak bonds between electropositive and electronegative groups

32
Q

Draw a happen carrier complex

A

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MIIM30002 - Principles of Immunology (30 decks)

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