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Block 4 > Immunigens, Antigens, And Antibodies > Flashcards

Immunigens, Antigens, And Antibodies Flashcards

1
Q

What are immunogens?

A

Any substance that can trigger an immune response in the body
All immunogens are antigens

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2
Q

What are antigens?

A

Any substance that is specifically recognized by the immune system
Not all antigens are immunogens

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3
Q

What are the 5 requirements for immunogenicity?

A
  • Foreignness
  • Size (>6kD)
  • Chemical complexity
  • Degradability
  • Dosage
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4
Q

What are epitopes?

A

Regions on an antigen that are recognized by the immune system —> immune response

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5
Q

Are all antigens immunogens?

A

No, all immunogens are antigens, but not all antigens are immunogens.

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6
Q

What is the specific binding property of antigens?

A

Antigens bind specifically to antibodies or T cells.

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7
Q

What is a requirement for immunogenicity related to foreignness?

A

Immunogens must be foreign; the more foreign, the more immunogenic.

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8
Q

What molecular weight is generally immunogenic?

A

Molecules greater than 6kD are generally immunogenic.

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9
Q

Are homopolymers of amino acids immunogenic?

A

No, they are not immunogenic due to low chemical complexity.

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10
Q

What is necessary for antigen presentation?

A

If a substance can’t be broken down, it can’t be presented
- Susceptible to enzymatic degradation
- Stable for antigen presentation

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11
Q

What can insufficient antigen dosages cause?

A

Insufficient doses may lead to tolerance.

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12
Q

What is a hapten?

A

A low molecular weight molecule that is non-immunogenic by itself but can be immunogenic when conjugated with a carrier.

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13
Q

What type of molecule is rarely immunogenic?

A

Lipids are rarely immunogenic.

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14
Q

Which class of molecules is highly immunogenic?

A

Proteins and glycoproteins are highly immunogenic.

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15
Q

What is cross-reactivity in immunology?

A

The ability of an antibody to react with a second, closely related antigen.

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16
Q

What is the role of adjuvants in immunogenicity?

A

Adjuvants enhance immunogenicity by prolonging antigen persistence, causing inflammation, or improving immune cell processing.

17
Q

Why are antibodies important? (5)

A
  • Neutralize toxins/viruses
  • Immobilize bacteria/parasites
  • Activate complement
  • Start opsonization
  • Antibody-dependent cell mediated cytotoxicity (ADCC)
18
Q

Where are hypervariable regions located in antibodies?

A

Hypervariable regions are located in both the light and heavy chains of antibodies.

19
Q

What are the five major classes of antibodies?

A

IgG, IgA, IgM, IgE, and IgD.

20
Q

What is unique about IgG antibodies?

A

IgG can cross the placenta, activate complement, and mediate ADCC.

21
Q

What is the primary function of IgA?

A

IgA provides defense on mucosal surfaces and is abundant in secretions.
Antiviral and antibacterial

22
Q

What does IgE mediate?

A

IgE mediates Type I hypersensitivity reactions and is elevated during parasitic infections.

23
Q

What is the first immunoglobulin produced after infection?

A

IgM is the first immunoglobulin produced and is efficient at complement fixation.

24
Q

What adjuvant is approved for human use?

A

Aluminum hydroxide or phosphate

25
Q

What is the hypervariable region of the antibody made of?

A

Heavy and light chains

26
Q

What is the function of the hypervariable region on the antibody structure? (3)

A
  • Antigen binding: happens at prongs of “Y” structure and interact with epitope
  • Specificity
  • Diversity and variability: 3 hypervariable regions in the prongs of the “Y” structure
27
Q

Explain antibody-dependent cell mediated cytotoxicity

A
  • Bridges innate and adaptive immune system
  • Ig coat target cells (tumour, infected cells) and mark them for destruction by effector cells (NK, macrophages, neutrophils, and eosinophils)
28
Q

What are the structural differences between IgG, IgA, and IgM?

A
  • IgG: monomer
  • IgA: dimer
  • IgM: pentamer
29
Q

What Ig is unchanged in a secondary response?

A

IgM

30
Q

What Ig is most increased in a secondary response?

A

IgG

31
Q

What is complement fixation?

A
  • Complement system activation
  • Complement becomes fixed to pathogen or antibody-antigen complex surface
  • Above leads to cascade of rxns to remove pathogens
32
Q

What Ig is unchanged in viral or bacterial infection?

A

IgE — only changes with parasitic infection

33
Q

What Ig mediates Type I hypersensitivity rxns?

A

IgE

34
Q

How does IgE mediate allergic rxns?

A
  • Allergen: harmless substance ID as threat
  • First exposure to allergen —> preparing response for next exposure
  • Re-exposure —> IgE x-linking —> histamine and cytokines release

Block 4 (6 decks)

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