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Immunology Exam 1 > L6: Antibodies & Antigens > Flashcards

L6: Antibodies & Antigens Flashcards

1
Q

another name for abs

A

immunoglobulins

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2
Q

most abs are found in the _____ slowest _______ group of globulins, named ____ globulins for the third letter of the greek alphabet

A

third slowest migrating group of globulins

named gamma globulins

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3
Q

effector properties of abs

A
  1. reduce damage to host from inflammatory response
  2. organized t cell response
  3. opsonization
  4. activation of complement
  5. toxin neutralization
  6. direct antimicrobial activity
  7. immunomodulation
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4
Q

basic structure of abs

A

basic unit = 4 polypeptide chains – 2 light L chains

—2 heavy H chains

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5
Q

how are abs chains bound together?

A

by covalent disulfide bridges
and
noncovalent interactions

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6
Q

both H and L chains are divided into ?

A

V and C regions

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7
Q

V region

A

contain the ag binding site

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8
Q

C region

A

determine the fate of the ag bound in the V region

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9
Q

abs can be proteolytically cleaved to yield?

A

2 Fab fragments

1 Fc fragment

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10
Q

Fab fragments

A

fragment ag-binding

2 short arms of the Y

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11
Q

Fc fragment

A

fragment crystallized
responsible for effector functions

stem of the Y

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12
Q

IgG is cleaved by enzymes ____, where on the ab?

A

papain

at the 3-way junction of the Y shape

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13
Q

Papain digestion of IgG

A

allows separation of 2 Fab fragments and Fc fragment

Fc receptors then bind Fc fragment

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14
Q

proteolysis of IgG by pepsin

A

pepsin generates a single bivalent antigen-binding fragment = F(ab’)2

Stem + (2 arms still connected)

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15
Q

types of H chains

A

there are 5 dif types
greek letters or
IgM, IgD, IgG, IgE, IgA

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16
Q

types of L chains

A

2 types
k and gamma

each with a MW of 23 kDa

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17
Q

each Ab unit can have only what type of L chain?

A

k or y

cannot have both

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18
Q

both H and L chains have intrachain _______ bridges every _____ amino acid residues, which create ?

A

disulfide bridges
90 aa

polypeptide loops/domains of 110 amino acids (these domains are named by location)

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19
Q

Ig superfamily proteins

A

a large group of cell surface soluble proteins

are involved in the recognition, binding, adhesion processes of cells

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20
Q

Ig superfamily types

A 
T cell receptor
MHC molecules
CD4 coreceptor
CD28
ICAM-1
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21
Q

secreted IgG

A
  1. ag binding site formed by Vl and Vh domains
  2. heavy chain C regions end in tail pieces
  3. complement and Fc receptor binding sites w/in heavy chain
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22
Q

membrane bound IgM on ___ cell

A

B cells

1 more Ch4 domain than IgG

C-terminal transmemb portion
cytoplasmic portion to anchor on memb

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23
Q

abs have great flexibility due to ?

A

hinges – the junction point of the Y

hinge region located between Ch1 and Ch2 domains

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24
Q

what is the importance of ab flexibility?

A

allows them to attach to widely spaced cell surface determinants or to closely spaced ones

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25
how do abs recognize ags?
conformational determinant linear determinant neoantigenic determinant
26
conformational determinants
ab has selective binding for specific conformation of ag so determinant is lost if ag is denatured
27
linear determinant
Ig binds to determinant in denatured protein only or Ig can bind to native and denatured forms
28
neoantigenic determinant
this is created by proteolysis determinant near site of proteolysis
29
define abs affinity
the tightness of ag-ab binding is called affinity dif abs will differ in their affinity for one ag
30
when the binding constant is higher ?
it is less likely the ab will dissociate from the ag
31
which abs generally have lower affinity for ags?
abs produced in the primary response soon after injection of an ag
32
which abs generally have higher affinity for ags?
abs produced by a memory response association constants 1000x higher
33
when is affinity especially critical?
when the ag is a toxin or virus and must be neutralized rapidly at low titers
34
define valence of abs
the maximum number of antigenic determinants w/ which it can react
35
explain valence of IgG
it has 2 Fab regions thus can bind 2 molecules of ag or 2 identical sites on same particle thus its valence = 2
36
relate valence and binding affinity
valence is important for increased binding affinity having 2 or more binding sites for an ag can greatly increase the tightness of binding
37
define avidity
a measure of the overall strength of an ab-ag complex
38
avidity is dependent upon ?
1. affinity of ab for epitope | 2. valence of both ab and ag
39
compare the low affinity of IgM to IgG's high affinity
the low affinity can be extremely effective in neutralizing a microorganism because of large number of binding sites (valence)
40
changes in properties of abs produced by plasma cells
1. increased affinity when memb bound 2. secreted form changes from b cell receptor function to effector function 3. isotype switching form -- each isotype serves a dif set of effector functions
41
which ab has a secretory component?
iga
42
which ab has a J chain?
iga | igm
43
which ab is formed by heavy and light chains only?
igg igd ige
44
proliferation cytokines for activated b cells
IL-2 IL-4 IL-5
45
differentiation cytokines for activated b cells
IL-2, 4, 5 IFN-y TGF - b
46
cytokines can _______ the ab classes ________ by a differentiating ___ cell
regulate produce by b cell
47
cytokine IFN-y stimulates ?
IgG2a or IgG3 IgG3 = phagocytosis
48
cytokine TGF - b stimulates ?
IgA or IgG2b IgA = mucosal defenses
49
cytokine IL-4 stimulates ?
IgE = allergy or IgG1 = phagocytosis
50
cytokine IL - 2, 4, 5 stimulates ?
IgM = complement activation
51
influence of cytokines on ab isotype switching: IL-5 + IgA = ?
augments production of dif isotype
52
why are several classes of abs needed?
dif microbes have dif biological properties and can enter the body thru dif routes dif abs are needed for dif types of microbes and dif locations
53
it is likely that the 5 different ab classes and their subclasses have evolved to ?
facilitate protection against microbes entering at dif sites
54
list the most common use for each type of ab
``` iga = mucosal secretions igm = mainly found in plasma ige = absorbed by mast cells igg = penetrates deeper into tissues ```
55
what are the subclasses of IgG and IgA?
igg1 igg2 igg3 igg4 iga1 iga2
56
which ab comprises 15% of all abs in healthy serum?
iga
57
IgA in serum vs IgA in secretions. give examples of secretions
monomeric vs a dimer w/ a joining peptide ex. tears, saliva, mucus, sweat, gastric fluid
58
what can ags can Ig bind vs T cell receptor
proteins, lipids, carbs, small chemicals proteins only peptide-MHC complexes
59
IgG is found where ?
vascular and extravascular spaces | and in secretions
60
what ab is the most abundant in the blood?
igg
61
which ab provides the bulk of immunity to most bloodborne pathogens?
igg
62
what separates the subclasses of IgG?
they each have slightly dif sequences in their H chains which results in dif functions
63
which is the only ab that can cross the placenta to provide?
igg passive humoral immunity to fetus and infant at birth
64
how does maternal ab cross the placenta
epithelium of placenta have receptor for Fc regions (FcRn) for maternal igg thus allowing maternal igg to enter fetal circulation
65
function of maternal ab crossing the placenta
1. provide protection prior to generation of immunocompetence 2. protection for infant since immune system takes weeks to catabolize the maternal igg
66
what is the primary function of IgD
an ag receptor on b cells probably also involved in regulating b cell function when encountering an ag
67
naïve b cells express what abs?
igm and igd in 50/50 ratio but both are specific for same ag
68
IgM and IgD on a b cell
act as receptors for ag ag is internalized and processed then presented to helper T cells
69
ag activated b cells will?
proliferate differentiate into plasma cells thus initiating a humoral immune response
70
IgM on a b cell is expressed as ?
a 4 chain unity 2 H chains, 2 L and is the 1st ab produced by ag activated b cell prior t to Th cell interaction
71
critical role of IgM
role in defense before sufficient igg quantities have be produced
72
blood IgM
composed of 5 4-chain units held together by disulfide bridges thus has high avidity
73
J-chain on IgM
inititates polymerization of subunits during secretion from a plasma cell
74
IgM is a big molecule and thus is found primarily in ?
the bloodstream
75
the major Ig present in external secretions such as colostrum, milk, saliva, etc
iga
76
IgA structure
in addition to L and H chains 2 other polypeptide chains - -1 secretory component SC - -J chain
77
SC
secretory component of iga part of the poly-Ig receptor involved in transepi migration of exocrine iga and stabilizes iga against proteolytic degradation in GI tract
78
synthesis of IgA
most occurs locally by plasma cells in mammary and salivary glands along the respiratory, GI, and GU tracts
79
serum IgA
monomer composed of 4 polypeptide chains | 2 L, 2 H
80
how does IgA work in mucosal secretions?
bind to pathogen derived ags prevent their attachment or invasion of epithelial cells
81
IgE levels in serum
very low levels
82
IgE role
enhancing acute inflammation | protection from worms and allergic rxns
83
ab-mediated allergy is predominantly associated w/ ?
ige
84
when ag is reintroduced to sensitized mast cells
ag binds to ige on mast cell triggers activation and release of mediators
85
IgE is an important components of immediate ?
hypersensitivity syndromes such as: hay fever asthma

Immunology Exam 1 (8 decks)

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