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Immunology > Antibodies and Antigens (Lec 6) > Flashcards

Antibodies and Antigens (Lec 6) Flashcards

1
Q

Are antibodies and immunoglobulins interchangeable terms?

A

yes

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2
Q

most abs are found in the third fastest migrating group of globulins called what?

A

gamma globulins

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3
Q

What are the effector properties of the light chain part of abs?

A

direct antibacterial activity; immunomodulation

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4
Q

What is the effector property of the heavy chain part of abs?

A

toxin neutralization

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5
Q

What is the effector property of the variable region part of abs?

A

reduced damage to host from inflammatory response

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6
Q

What are the effector properties of the Ab combining site (Fab) part of abs?

A

organized T-cell response; opsonization

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7
Q

What is the effector property of the constant regions (Fc region) of abs?

A

activation of complement

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8
Q

Abs have a basic unit of four polypeptide chains - two light chains and two heavy chains. What keeps the chains bound together?

A

covalent disulfide bridges and non covalent interactions

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9
Q

Abs can be proteolytically cleaved to yield how many Fab and Fc fragments?

A

2 Fab fragments

1 Fc fragment

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10
Q

Both H and L chains are divided into V and C regions. What do the V and C regions contain?

A

V region contains Ag binding site

C region determines fate of the Ag

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11
Q

There are five different kinds of H chains which determine what?

A

the class of antibody (IgM, IgD, IgG, IgE, and IgA)

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12
Q

How many toes of L chains are there?

A

2: k and gamma, each with a MW of 23 kDa

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13
Q

True of false?

Each Ab unit can have only k or gamma L chains but not both

A

true

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14
Q

Both H and L chains have intrachain disulfide bridges every __ amino acid residues

A

90

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15
Q

What do intradisulfide bridges create in H and L chains?

A

polypeptide loops, domains of 110 amino acids

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16
Q

The domains domains created by intradisulfide bridges are referred to as what?

A

Vh, Vl, Ch1, Ch2, etc

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17
Q

In regards to secreted IgG, the Ag binding site is formed by the juxtaposition of what two domains?

A

Vl and Vh

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18
Q

True or False?

In regards to secreted IgG, the H chain C regions end in short pieces

A

false, tall pieces

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19
Q

True or false?

In regards to membrane-bound IgM on B cellls, there is one more Ch domain than IgG has

A

true

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20
Q

Membrane-bound IgM on B cell has C-terminal transmembrane and cytoplasmic portions that do what?

A

anchor the molecule in the plasma membrane

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21
Q

IgG is cleaved by what enzyme which results in 2 Fab fragments and an Fc fragment?

A

Papain

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22
Q

This enzyme cleaves IgG and generates a single bivalent antigen-binding fragment, F(ab’)2

A

Pepsin

note: there are also small peptide fragments as a result of cleavage

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23
Q

What is the role of hinge regions in abs?

A

provides flexibility between in regions between the Ch1 and Ch2 domains

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24
Q

The Ig superfamily is a large group of cell surface and soluble proteins that are involved in what?

A

recognition, binding, or adhesion processes of cells

examples: T cell receptor; MHC molecules; the CD4 receptor of T cells; CD28, a costimulatory receptor on T cells; and the adhesion molecule ICAM-1

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25
Q

Compare the on-rate/off-rate of Ig and TCR in regards to Ag binding

A

Ig - rapid on-rate, variable off-rate

TCR - slow on-rate, slow off-rate

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26
Q

What are CDRs?

A

complemtarity-determining regions from the H and L chain: loops that protrude from the surface of the two Ig V domains and in combination create an Ag-binding region

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27
Q

Each CDR is composed of how many antiparallel beta strands?

A

two; form two beta-pleated sheets held together by a disulfide bond

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28
Q

The tightness of Ag-Ab binding is called what?

A

ab affinity

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29
Q

Abs formed in the primary response soon after the injection of an Ag are generally higher or lower in affinity?

A

lower

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30
Q

Abs produced by a memory response have a higher or lower affinity than those in a primary response?

A

higher affinity

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31
Q

True or false?

Affinity of an Ab is critical when the Ag is a toxin or virus and must be neutralized rapidly

A

true

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32
Q

The valence of an Ab is the maximum number of ___ ___ with which it can react

A

antigenic determinants

33
Q

IgG contain two Fab regions and can bind two molecules of Ag or two identical sites on the same particle, thus having a valence of what?

A

2

34
Q

Valence is important for binding affinity, as having two or more binding sites for an Ag can dramatically increase or decrease the affinity?

A

increase

35
Q

The combined effect that results from synergy of the binding strengths of each binding site is called what?

A

avidity

36
Q

Ab with a low affinity for an Ag determinant but with a large number of binding sites, for example IgM as compared to IgG, can be extremely effective in doing what?

A

neutralizing a microorganism?

37
Q

True or false?

Polyvalent relates to low avidity of interaction

A

false, very high avidity of interaction; the more valency present, the more avidity of interaction

38
Q

Match the following stage of B cell development with its pattern of Ig production:
stem cell

A

none

39
Q

Match the following stage of B cell development with its pattern of Ig production:
Pre-B cell

A

cytoplasmic u H chain and Pre-B receptor

40
Q

Match the following stage of B cell development with its pattern of Ig production:
Immature B cell

A

membrane IgM

41
Q

Match the following stage of B cell development with its pattern of Ig production:
Mature B cell

A

membrane IgM, IgD

42
Q

Match the following stage of B cell development with its pattern of Ig production:
Activated B cell

A

low rate Ig secretion; H chain isotype switching; affinity maturation

43
Q

Match the following stage of B cell development with its pattern of Ig production:
Ab-secreting cell

A

high rate Ig secretion; reduced membrane Ig

44
Q

Match the following change in antibody structure to its functional significance in antigen recognition and its effector function:
affinity maturation

A

Antigen recognition: increased affinity

Effector function: no change

45
Q

Match the following change in antibody structure to its functional significance in antigen recognition and its effector function:
change from membrane to secreted form

A

Antigen recognition: no change

Effector function: change from B cell receptor function to effector function

46
Q

Match the following change in antibody structure to its functional significance in antigen recognition and its effector function:
Isotype switching

A

Antigen recognition: no change

Effector function: each isotope serves a different set of effector functions

47
Q

IgA is the most common Ab in what?

A

mucosal secretions

48
Q

IgM is mainly found in what?

A

plasma

49
Q

IgE is absorbed on the surface of what?

A

mast cells

50
Q

IgG penetrates deeper into what?

A

tissue

51
Q

What is the most abundant Ig in the blood?

A

IgG

52
Q

True or false?

IgG provides the bulk of immunity to most bloodborne pathogens

A

true

53
Q

IgG is the only Ab to cross the placenta to provide what type of immunity to the developing fetus and to the infant on its birth?

A

passive humoral immunity

54
Q

What type of H and L chains do IgG Abs have?

A

two H gamma chains

either two k or two lambda L chains

55
Q

Subclasses of IgG have slightly different sequences in their H or L chains that result in differences in their functional activities?

A

H chains

56
Q

The epithelial cell surface receptor for Fc regions (FCRn) of maternal IgG is present where?

A

in the placenta

57
Q

FCRn does what?

A

transfers maternal IgG to the fetal circulation

58
Q

True or false?
IgA is the major Ig present in external secretions such as colostrum, milk, and saliva where it exists as a 420 kDa dimer

A

true

59
Q

In addition to the k or lambda L chains and the H alpha chain, the secreted IgA also contains two other polypeptide chains. What are they?

A

Secretory component (SC) and joining chain (J-chain)

60
Q

SC is part of the poly-Ig receptor involved in the ____ ____ of exocrine IgA and stabilizes IgA against proteolytic degradation

A

transepithelial transport

61
Q

The two Ig units composing secretory IgA are held together by what?

A

the J-chain through disulfide bridges

62
Q

Most IgA is synthesized locally by what?

A

plasma cells in mammary and salivary glands, and along the respiratory, GI and GU tracts

63
Q

IgA exists as a 170 kDa, four polypeptide chain protein where?

A

in the serum

64
Q

What is the first Ab produced by a B cell?

A

IgM

65
Q

Initially, IgM acts as what?

A

a BCR for B cells

66
Q

IgM is big molecule (900kDa) and therefore found primarily where?

A

in the bloodstream

67
Q

IgM are of particular importance before when?

A

before sufficient quantities of IgG have been synthesized

68
Q

The overall avidity of an IgM is quite high, making IgM very effective in doing what?

A

removal of the microbe

69
Q

What is the primary function of IgD?

A

Ag receptor on B lymphocytes

70
Q

True or Fasle?

B cells can’t express both IgM and IgD

A

false; B cells can express both and both are specific for the same Ag

71
Q

When IgM and IgD expressed on a B cell interact with an Ag for which they are specific, what happens?

A

Ag is internalized, processed, and presented to helper T cells

72
Q

B cells activated by B cell receptors proliferate and differentiate into ___ ___ thus initiating the development of a humoral immune response

A

plasma cells

73
Q

IgE is present in the serum at very low levels and plays a significant role in what?

A

enhancing acute inflammation, protection from infection by worms, and allergic reactions

74
Q

Ab-mediated allergy is predominantly associated with which Ig?

A

IgE

75
Q

IgE binds to receptors on mast cells which are specific for the __ region of IgE

A

Fc

76
Q

When Ag is reintroduced to such “sensitized” mast cells, it binds to IgE molecule on the mast cell and triggers what?

A

release of mediators

77
Q

IgE is an important component of immediate hypersensitivity syndromes such as?

A

hay fever and asthma

78
Q

In regards to production of monoclonal Ab, splenocytes from an immunized mouse are isolated and fused with myeloma cells to form hybrid cells with the help of what?

A

polyethylene glycol

79
Q

Myeloma cells have immortalized properties but do not secrete what?

A

their own Ig

Immunology (12 decks)

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