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M3: Immunology > Immunoglobulins > Flashcards

Immunoglobulins Flashcards

1
Q

What is another name for antibodies?

Where is it present? Product of which system?

Secreted by?

A
  • immunoglobulins
  • present in plasma, tissues, secretions and lymphatics
  • product of humoral immune system
  • secreted by activated B cells - plasma cells
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2
Q

How many classes of immunoglobulin are there?

What are their names?

Function?

A

There are 5 classes of immunoglobulin:

  • IgG
  • IgM
  • IgA
  • IgD
  • IgE

Provide recognition function and trigger effector functions

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3
Q

What region is at the N-terminus of an antibody?

C-terminus?

What are the regions of an antibody?

  • Upper:
  • Lower:
  • Inbetween:
A
  • N-Terminus: variable region
  • C-Terminus: constant region
  • Upper region: Fab arms
  • Lower: Fc region
  • Inbetween is a flexible region, part of the heavy chain: hinge
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4
Q

Where do we have disuphide bridges?

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A
  • Hinge - site of inter-heavy chain disulphide bonds
  • Between light and heavy chains
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5
Q

What is the dual function of antibodies?

A
  • Recognition function: binding to antigen by Fab arms
  • Effector function: clearance mechanisms to get rid of foreign material, occurs through interaction of Fc with effector molecules
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6
Q

What are the two types of light chains in humans?

Can light chains be different in an individual antibody?

What are the two globular domains

A
  • Lambda and kappa chains
  • No, both light chains are the same in any individual antibody molecule
  • Variable light domain (VL) and Constant light (CL)
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7
Q

Which chain determines the class of antibody?

Why?

A

The heavy chain determines class of antibody because the light chains are the same in all classes

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8
Q

Name the heavy chain for each type of immunoglobulin:

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How many globular domains do these heavy chains fold up into?

Name them:

A
  • IgG: gamma heavy chain
  • IgA: alpha
  • IgM: mu
  • IgE: epsilon
  • IgD: delta

Fold up into 4 or 5 globular domains:

  • Variable heavy (VH), constant heavy (CH) 1, CH2, CH3 and (CH4)
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9
Q

Name the key effector molecules:

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-

A
  • Fc receptors
  • Complement
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10
Q

What are CDRs?

A

Complementarity determining regions are key parts that determine which antigen they are going to bind to.

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11
Q

How many CDRs are their?

What do they create?

A

There are 6 CDRs, 3 from VH and 3 in VL domains

They create the antigen binding site

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12
Q

Where is the anitgen binding site found?

What is it formed from?

What do they form?

A
  • At the tip of each Fab arm
  • Formed from 6 hypervariable regions: 3 in VH and 3 in VL
  • A unique 3D structure, site for binding antigen, only allowing the complementary antigen to bind, therefore high specificity and high affinity for binding
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13
Q

IgG

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A
  • most abundant Ig in plasma (10mg/ml)
  • Y shaped, 2 heavy chains, 2 light chains
  • 4 subclasses: IgG1, IgG2, IgG3, IgG4
  • very efficient at triggering complement and phagocytosis via Fc receptors
  • only Ig class to cross placenta from mother to foetus - protects baby in first months of life
  • predominant antibody of secondary response
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14
Q

IgM

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A
  • Only in plasma and secretions: too large to enter tissues
  • 5 Y shaped units held together by J chain and disulphide bridges
  • heavy chain has 5 globular domains
  • 10 antigen binding sites for antigen - good at clumping viruses together
  • very efficient at activating complement
  • predominant antibody of primary response
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15
Q

What does agglutinating mean?

A
  • clumping virus particles together
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16
Q

IgA

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A
  • second most prevalent after IgG
  • major antibody in seromucous secretions e.g. saliva, milk, gut
  • class of antibody first encountered by many invading bacteria and viruses
  • two subclasses: IgA1, IgA2: exist in monomeric and dimeric forms
  • secretory component protects in harsh environment
17
Q

What does IgE do?

A
  • Interacts with FceR1
  • also important against parasitic infections
18
Q

IgD

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A
  • very low serum concentrations
  • found on surface of lymphocytes
  • function unclear - thought to be involved in control of antibody response
19
Q

What are the key effector molecules that immunoglobulins interact with?

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A
  • Fc receptors: receptors which bind specifically to Fc region of immunoglobulins
  • Complement
20
Q

Binding of antibody-coated targets to FcR on immune cells can result in:

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A
  • phagocytosis
  • release of activated oxygen species and enzymes
  • release of inflammatory mediators e.g. histamine
  • enhanced antigen presentation
  • clearance of immune complexes
21
Q
A

M3: Immunology (8 decks)

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