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Host Defense Exam 1 > Immunoglobulin Structure > Flashcards

Immunoglobulin Structure Flashcards

1
Q

What is the main function of each Ig isotype? (MAGDE)

A 
IgM = primary response
IgA = mucosal immunity
IgG = secondary response; can cross placental barrier
IgD = on B cell surface
IgE = allergic hypersensitivity
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2
Q

Describe the core structure of an antibody.

A

2 Heavy chains - variable region and constant region; indicates isotype
2 Light chains - variable region and constant region
variable regions determine antigen specificity

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3
Q

What does the antigen-binding site of the variable regions bind to?

A

epitope - 6-8 AAs on an antigen

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4
Q

Which Ig isotypes have more than one subtype?

A 
IgA = 2
IgG = 4
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5
Q

How many kinds of light chains are there?

A

kappa

lambda

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6
Q

On which terminal of the heavy and light chains is the variable region found?

A

N terminal

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7
Q

What functions do the constant regions carry out?

A
  • determines if it can cross the placenta
  • determines binding to Fc receptors on monocytes, mast cells, and macrophages
  • determines binding to complement
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8
Q

What are CDRs?

A

complementarity-determining regions

  • 3 regions of hypervariability in AA sequence
  • stick out as loops off the variable region’s antigen binding site
  • determines specificity to antigen
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9
Q

What is the Fab fragment? Fc?

A

Fab = antigen binding fragment; made up of VH and VL, constant region of the light chain, and one domain of the constant heavy chain region

Fc = crystallizable; made up of the heavy chain base; used to create antibodies against Ig

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10
Q

How would you detect presence of IgM in a solution?

A

use anti-mu antibodies that would bind to the IgM heavy chain (mu)

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11
Q

Describe the structure(s) of IgM.

A
  • transmembrane = monomeric; found on B cells; part of B-Cell Receptor
  • serum = pentameric; joined by J chain
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12
Q

Which antibodies can be involved in complement?

A 
IgM
IgG (depending on subclass)
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13
Q

Rank the antibodies by their serum concentration.

A 
IgG
IgA
IgM
IgD
IgE
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14
Q

Describe the structure of IgG.

A

monomeric

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15
Q

Which antibody can cross the placenta?

A

IgG via FcRn receptor

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16
Q

Describe the structure of IgD.

A

monomeric and transmembrane

found on B cells, part of BCR

17
Q

Describe the structure of IgE

A

monomeric

secreted

18
Q

Describe the activation of IgE during allergic hypersensitivity.

A
  1. Fc-epsilon receptors are found on the surface of mast cells, basophils, etc.
  2. IgE binds to the receptors
  3. allergen binds to 2 neighboring IgE molecules, causing the cross-linking of heavy chains
  4. signal cascade leads to degranulation
19
Q

Describe the structure(s) of IgA.

A

secretory/mucosal IgA = dimeric, held together by J chain

serum IgA = monomeric

20
Q

Which is the most produced antibody?

A

IgA
80% of immunoglobulin production is IgA
constantly being made

21
Q

Describe neutralization.

A

antibody binds to antigen
prevents adherence to host cells
prevents entrance

22
Q

Describe opsonization

A

antibody binds to antigen
Fc Ig binds to Fc receptors on phagocytes
facilitates phagocytosis of invader

23
Q

Describe complement activation

A

antibody binds to antigen
antibody binds to complement receptor on phagocytes
facilitates enhancement of opsonization
leads to lysis of invader

24
Q

Describe serum levels of antibodies around the time of birth.

A
  • passively transferred maternal IgG lasts about 3 months after birth (due to half-life)
  • IgM is the first to be produced by newborns and reaches adult levels after 9 months
  • IgG is the second to be produced by newborns and reaches adult levels after 4 years
  • IgA is the last to be produced by newborns and reaches adult levels after 10 years
25
Q

What are polyclonal antibodies?

A

antibodies are produced by different B cells and against different epitopes of the same antigen
- found in the serum of immunized individuals

26
Q

What is a clinical use of polyclonal antibodies?

A

IVIG

- infusion of Ig into an individual

27
Q

What are monoclonal antibodies?

A

antibodies produced by a single B cell with the same epitope binding site

28
Q

What is a clinical use of monoclonal antibodies?

A
  • against a specific tumor

Host Defense Exam 1 (12 decks)

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