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Immunology > Immunoglobulins > Flashcards

Immunoglobulins Flashcards

1
Q

Define antibody’s role

A

Glycoproteins secreted into serum in response to exposure to antigens

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2
Q

What were the 4 fractions when electrophoresis was carried out on serum?

A

Albumin
Alpha, beta and gamma globulin

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3
Q

Why were antibody molecules considered Gamma-globulins?

A

Most antibody activity is found in gamma fractions of the globulin

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4
Q

What are the two functionally distinct fragments of antibodies?

A

Fab = fragment antigen-binding
Fc = fragment crystallizaable

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5
Q

What are the functions of the distinct antibody regions?

A

Fab = antigen binding
Fc = effector function

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6
Q

What enzyme was used to cleave the antibody, and what type of cleavage was it?

A

Papain proteolytically cleaved the antibody into 3 fragments

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7
Q

Where does pepsin cleave the antibody?

A

Towards the C-terminal side of the disulphide bond
Splitting the antibody into Fab and Fc domains

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8
Q

When cleaved what can fragment I and II still do?

A

Retain the power to combine with the antigen

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9
Q

Properties of fragment III

A

Crystallizes easily
Has much of the antigenic specificity of the original molecule

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10
Q

What causes the antibody to dissociate into Light and Heavy chains?

A

Reduction of the disulphide bonds in antibodies = occurs in presence of denaturing agents

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11
Q

What are the molecular weights of L and H chains?

A

25kDa and 50kDa

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12
Q

How many chains and what molecules weight is IgG?

A

2 LC and 2 HC = 150kDa

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13
Q

What is the function of the hinge region?

A

Give flexibility
Create different bond angles between Ig arms

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14
Q

Where is hypervariability found?

A

Primary amino acid sequence of V regions

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15
Q

How are complementarity-determining regions formed?

A

3 hypervariable regions are separated in primary structure
CVD are formed when they come together in tertiary structure

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16
Q

What is the complementarity-determining region?

A

Antigen binding site

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17
Q

What separates the CDR?

A

Framework regions = highly conserved regions of the variable portion of the antibody

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18
Q

How many CDRs are involved when antibody and antigen interact?

A

6

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19
Q

What are Fr receptors?

A

Receptors on effector cells that bind antibodies’ Fc region

20
Q

What cells express receptors for antibodies?

A

Macrophages
Dendritic cells
Mast cells
Eosinophils
NK cells

21
Q

How many major types of light chains are there?

A

2 = kappa or lambda

22
Q

What are the 5 major genes that encode the heavy chains?

A

Gamma
Mu
Delta
Alpha
Epsilon

23
Q

What is special about the function of IgG?

A

Only IgG is transferred from mother to fetus
It is the only Ig that can cross the placenta

24
Q

When are there transient low levels of IgG?

A

2-4 months old
Disease susceptible period

25
Q

How do different subclasses occur?

A

Structural and functional differences

26
Q

Give examples of subclass structural differences

A

Different number of disulphide bonds
Different size of hinge region

27
Q

Give examples of different physiochemical properties of IgG subclasses

A

Serum concentrations
Serum half lives

28
Q

What form is IgA present in the serum (circulation)?

A

Monomeric

29
Q

What form is IgA present in secretion?

A

Dimeric

30
Q

What is the function of the J chain?

A

J chain regulates the multimerization of IgM and IgA in mammals

31
Q

What does the antibody isotype determine?

A

Effector function

32
Q

What are the 5 effector functions?

A
  1. Antibody dependent cellular cytotoxicity (ADCC)
  2. Degranulation of mast cells and eosinophils
  3. Opsonization of pathogens
  4. Recruitment of complement
  5. Neutralization of bacteria, viruses and toxins
33
Q

What are the functions of antibodies and how is this function carried out?

A

Protect us by recruiting other effector functions
Through interaction of Fc with other cells

34
Q

How do antibodies neutralize viruses?

A

Antibodies bind to the viruses, preventing the virus from binding to cell surface receptors

Blocks fusion event

35
Q

Which antibodies neutralize toxins?

A

IgA and IgG

36
Q

How can we protect against toxic effects of venom?

A

Passive immunization

37
Q

What is antibody opsonization?

A

Process by which a pathogen is marked for phagocytosis

38
Q

How does opsonization enhance pathogen killing?

A

C3b binds CR1 receptor on effector cell

39
Q

What must occur to cross-link with Fc receptors on effector cells?

A

Antibody must be bound to antigen on pathogen = this allows Fc receptors on effector cell to bind the complex

40
Q

What cells mainly use antibody dependent cellular cytotoxicity?

A

NK cells

41
Q

What is antibody dependent cellular cytotoxicity?

A

The activation of NK cells by antibodies binding to its Fc receptor and binding to pathogen

NK then releases the enzyme perforin that punches holes in the pathogen, causing it to lyse

42
Q

What antibodies recruits eosinophils?

A

IgE

43
Q

What do eosinophils mainly attack?

A

Parasites

44
Q

How is degranulation activated?

A

IgE coats the parasite and eosinophil binds IgR through Fc receptor

Eosinophil degranulates and releases lysozymes and cytotoxic granules

45
Q
A

Immunology (8 decks)

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