antibodies and antigens Flashcards

1
Q

antibodies were orginally identified in the serum and termed _______ which is often used interchangeably with Abs

A

immunoglobulins

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2
Q

most Abs are found in the third slowest migrating group of globulins, named _____ globulins for the third letter of the greek alphabet

A

gamma

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3
Q

effector properties of Abs

A
  1. FcR (Fc receptor) - opsonization and phagocytosis of microbes
  2. activation of classical complement pathway
  3. toxin neutralization
  4. direct antibacterial activity - formation of three dimensional lattices (agglutination of bacteria) and wait for phagocytes to come and eliminate
  5. potential to modulate an immune response by immunization with AG-Ab complexes
  6. reduce damage to hose from inflammatory response
  7. organized T-cell (used to control acute T-cell mediated transplant rejection)
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4
Q

Abs have a basic unit of 4 polypeptide chains (2 light chains and 3 heavy chains) - bound together by covalent _______ _______ as well as by noncovalent interactions

A

disulfide bridges

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5
Q

both heavy and light chains are divided into _____ and _____ regions

A

variable (V)

constant (C)

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6
Q

the variable (V) region contains the ______ site and the constant (C) region determines the _____ properties of the Abs

A

Ag-binding

biological

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7
Q

Abs can be proteolytically cleaved to yield two ____ fragments and an ____ fragment that are responsible for effector functions

A

Fab (Fragment Ag-Binding)

Fc (Fragment Crystallized)

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8
Q

IgG is cleaved by what enzymes

A

papain and pepsin

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9
Q

papain digestion allows separation of ___ monovalent (having only 1 site of attachment) Fab fragments and complement and Fc receptors-binding the Fc fragment

A

2

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10
Q

pepsin digestion generates a single ______ Ag-binding fragment (F(ab’)2

A

bivalent (having two sites of attachment)

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11
Q

there are 5 different types of H-chains which determine the class of Ab

A

mu - IgM

delta - IgD

gamma - IgG

epsilon - IgE

alpha - IgA

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12
Q

there are 2 different types of light chains

A

kappa

lambda

(each with MW of 23kDa)

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13
Q

both heavy and light chains have intrachain disulfide bridges every 90 amino acid residues which create ______ ______ ; these Ig domains are referred to as ____ , ____, ____, and ____

A

polypeptide loops

Vh, Vl, Ch1, Ch2

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14
Q

a large group of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells belongs to the immunoglobulin superfamily they include:

A

T cell receptors

MHC molecules

CD4 coreceptor of T cells

CD28 (costimulatory receptor on T cells)

adhesion molecule ICAM-1

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15
Q

is IgG secreted or membrane-bound?

A

secreted

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16
Q

is IgM secreted or membrane-bound?

A

membrane-bound

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17
Q

secreted IgG:

the Ag-binding sites formed by juxtaposition of ___ and ___ domains

the heavy chain Constant regions end in ____ pieces

the locations of complement and Fc receptor - binding sites within the heavy chain constant regions are ____

A

VL and VH

tail

approximations

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18
Q

membrane- bound IgM:

has an additional ___ domain

CH4 domain has C-terminal transmembrane and ____ portions that anchor the molecule in the plasma membrane

A

CH4

cytoplasmic

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19
Q

hinge allows flexibility and abilty for Ab to bind to widely spaced cell surface determinants and closely spaced cell surface determinants; the hinge is located between what 2 domains?

A

CH1 and CH2

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20
Q

what Ags are recognized by Abs

A

conformational determinant

linear determinant

neoantigenic determinant (created by proteolysis)

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21
Q

different Abs vary in their _____ to the same Ag determinant

A

affinity

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22
Q

the higher the ____ constant (Ka) the less likely the Ab is to dissociate from the Ag

A

binding

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23
Q

Abs formed in the primary response soon after the injection of an Ag generally have ____ affinity (IgM)

A

lower

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24
Q

Abs produced by a memory response have ____ affinity than Ka in a primary response (IgG)

A

higher

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25
Q

the Ab affinity is critical when the Ag is a ___ or ___ and msut be neutralized rapidly at low titers of toxin or pathogen

A

toxin

virus

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26
Q

valence of an Ab is the ____ number of antigenic determinants with which it can react with Ag

A

maximum

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27
Q

molecule of IgG contains 2 Fab regions and it can bind 2 molecules of Ag or 2 identical epitopes on a single pathogen, and thus has a valence of ___

A

2

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28
Q

the valence is important for binding affinity, as having 2 or more binding sites for an Ag can dramatically increase the ____ of binding of the Ab to Ags

A

tightness

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29
Q

avidity gives a measure of the overall strength of an Ab-Ab complex. avidity depends on:

1.

2.

A
  1. affinity of the Ab for a single epitope

2. valence of both the Ab and Ab

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30
Q

low affinity IgM can be extremely effective in neutralizing a microorganism because it has 10x Ag binding ____

A

domains

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31
Q

Ig vs T Cell Receptor (TCR)

Ag-binding site:

A

Ig: three CDRs in VH and three CDRs in VL domains

TCR: three CDRs in Valpha and three CDRs in Vbeta domains

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32
Q

Ig vs T Cell Receptor (TCR)

Ag that may be bound

A

Ig: proteins, lipids, polysaccharides, and small chemicals

TCR: peptide-MHC complexes

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33
Q

Ig vs T Cell Receptor (TCR)

Antigenic determinants recognized

A

Ig: linear and conformation determinants of various macromolecules and chemicals

TCR: linear determinants; only 2 or 3 aa residues of a peptide bound to an MHC molecules

34
Q

Ig vs T Cell Receptor (TCR)

affinity of Ag binding

A

Ig: higher

TCR: lower

35
Q

Ig vs T Cell Receptor (TCR)

on-rate/off-rate

A

Ig: rapid on-rate ; variable off-rate

TCR: slow on-rate ; slow off-rate

36
Q

all 5 classes of Ig originate from B cells that contain what B-cell receptors

A

IgM or IgD

37
Q

original B-cell with B-cell receptor –> Ag binds –> affinity maturation (somatic mutations in variable region) –> _____ affinithy

A

increased

38
Q

original B-cell with B-cell receptor –> activated and differentiates into plasma cell –> change from membrane bound Ab to secreted form –> change from B-cell receptor function to ____ function

A

effector

39
Q

original B-cell with ……

A

.

40
Q

what chain of Ab determines class?

A

heavy chain

41
Q

what Ig classes have basic 4 chain Ab structure?

A

IgG

IgD

IgE

42
Q

what Ig class has dimer Ab structure

A

IgA

43
Q

what Ig class has pentamer Ab structure

A

IgM

44
Q

B cell proliferation cytokines

activated B cell IgM/IgD –> proliferating B cells

A

IL-2 IL-4 IL-5

45
Q

proliferating B cells —> cytokine _____ –> IgG3 (Phagocytosis)

A

IFN-gamma

46
Q

proliferating B cells –> cytokine ____ –> IgA (mucosal defenses)

A

TFG-beta

47
Q

proliferating B cells –> cytokine ____ –> IgE (allergy) and IgG1 (phagocytosis)

A

IL-4

48
Q

proliferating B cells –> cytokine ____ , ____ , ____ –> IgM (complement activation)

A

IL-2 IL-4 IL-5

49
Q

IgA is the most common Ab in

A

mucosal secretions

50
Q

IgM is mainly found in

A

the plasma

51
Q

IgE is absorbed on the surface of

A

mast cells

52
Q

IgG penetrates deeper into the

A

tissue

53
Q

IgA in serum is mainly _____ but in secretions (tears, saliva, mucus, sweat, gastric fluid) IgA is found as a _____ connected by a joining peptide

A

monomeric

dimer

54
Q

IgG functions

A

neutralization

opsonization

NK cell activation

complement activation

55
Q

maternal IgG is bound by placental

A

FcRn which is recycled

56
Q

placenta performs _____ immunity of fetus

A

passive

57
Q

IgD properties

A

low quantities in circulation

primary function: an Ag receptor on B lymphocytes

58
Q

when IgM and IgD is expressed on a B cell, they act as receptors for an Ag for which they are specific, the Ag is internalized, processed, and presented to _____ cells

A

helper T

59
Q

naive B cells express both ____ and ____ in approx 50/50 proportions

A

IgM and IgD

60
Q

what is the first Ab produced by any Ag-activated B cell prior to contact with T helper cells?

A

IgM

T-cell independent

61
Q

IgM heavy chain

A

2 mu heavy chains

62
Q

functions of IgM

A

complement activation*

activation of B cells, some neutralization (low affinity)

63
Q

what is the first Ig presented on developing B cell (BCR- B cell receptor)

A

IgM

64
Q

overall avidity of IgM is very ____ , making IgM very effective in removal of the microbe

A

high

65
Q

what Ig forms a pentamer in blood (J joining chain)

A

IgM

66
Q

IgM is a big molecule and therefore found primarily in the ______ and provides protection from ______ pathogens

A

bloodstream

bloodborne

67
Q

what is the most abundant immunoglobulin in the blood

A

IgG

68
Q

IgG provides the bulk of immunity to most ______ and ______ pathogens

A

bloodborne

tissue

69
Q

IgG has 2 heavy ____ chains with either 2 ____ or 2 ____ light chains

A

gamma

kappa

lambda

70
Q

heavy chain of IgA

A

alpha chains

71
Q

in addition to heavy and light chains, IgA also contains 2 other polypeptides chains, they are

A
  1. secretory component (SC)

2. J-chain (joining chain)

72
Q

IgA is found in the blood as a _____ and found in mucosa as a _____

A

monomer

dimer (J-chain)

73
Q

major function of IgA

A

neutralization in mucosa

74
Q

IgA stimulation of secretion:

A

interactions with Th cells in presence of TGF-beta

75
Q

IgA secretory component is responsible for

A

crossing epithelium

76
Q

what Ig is found in secretions (saliva and breast milk)

A

IgA

77
Q

IgA from breast milk provides newborn immunity in transition period between _____ and when the infant produces their own Ig

A

fetal IgG

78
Q

IgE is present in the serum at very ____ levels

A

low

79
Q

major functions of IgE

A

acute inflammation

protection from infection by worms and allergic rxns

activation of mast cells

80
Q

IgE is an important component of immediate hypersensitivity syndromes such as

A

hay fever and asthma

81
Q

production of monoclonal Ab

A
  1. splenocytes from a mouse that has been immunized with a known Ag are isolated
  2. myeloma cells have immortalized properties but do not secrete its own Ig
  3. isolated cells are fused with myeloma cells to form hybrid cells
  4. only Ab-secreting hybrid cells survive in HAT medium