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mbb 326 > lec 5- antibody structure > Flashcards

lec 5- antibody structure Flashcards

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1
Q

what are the three roles of antibodies in the immune response?

A

neutralization, opsonization, and complement activation

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2
Q

are antibodies the secreted from of B-cell receptors?

A

yes

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3
Q

how many epitopes is one antibody specific too?

A

one epitope for one antibody

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4
Q

what is an antigen?

A

any molecule or molecular fragment that is recognized by a B cell receptor or antibody and a T cell receptor in the context of a MHC molecule

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5
Q

what is an epitope?

A

the part of the antigen that binds antibody

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6
Q

where are epitopes for B cells?

A

on the surface of the pathogen

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7
Q

where are the epitopes for T cell receptors?

A

buried within the antigen

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8
Q

what is a multivalent antigen?

A

an antigen with more than one binding site

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9
Q

what are linear and discontinuous antigens?

A

linear: the binding is in order for 2 receptors
discontinuous: the binding occurs at two separated spots on the antigen

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10
Q

explain clonal selection and expansion:

A
  1. a single precursor cell gives rise to a large number of lymphocytes (B cells), each with different specificity
  2. removal of potentially self-reactive immature lymphocytes by clonal deletion
  3. pool of mature naive lymphocytes
  4. proliferation and differentiation of activated specific lymphocytes to form a clone of effector cells that can all secrete antibodies
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11
Q

do the cloned lymphocytes possess the same receptors with identical specificity to those of the parent cell?

A

yes

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12
Q

what do antibodies consist of? what bonds hold the heavy and light chains together?

A

-2 identical light chains
-2 identical heavy chains
-each light chain contains one variable region (of one domain) and one constant region (of one domain)
-each heavy chain consists of one variable region (of one domain) and one constant region (of 3 or 4 domains)
-disulfide bonds

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13
Q

what do the Vh and Vl domains make up?

A

the antigen-binding sites

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14
Q

what are the antigen binding sites on antibodies also called?

A

complimentary determining regions (CDRs)

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15
Q

what is the Fab fragment?

A

-fragment of antigen binding (Fab)
-composed of light chain and part of the heavy chain

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16
Q

what is the Fc fragment?

A

-fragment crystalizable (Fc)
-a portion of the constant region of the heavy chain

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17
Q

what does papain digestion do to an antibody?

A

-causes a cleave above the double bond, results in two Fab fragments and one Fc fragment

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18
Q

what does pepsin digestion do to an antibody?

A

-cleaves below the double bond and cuts the Fc fragment, results in one (Fab)2 fragment and multiple Fc fragments

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19
Q

what are the 5 classes of antibodies?

A

-IgM
-IgG
-IgD
-IgA
-IgE

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20
Q

what antibody class is the first to be produced?

A

IgM

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21
Q

what are the two classes of light chain?

A

kappa and lambda, no fucntional differences between the two

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22
Q

does the Fc region on antibodies bind to Fc receptors on the effector cells?

A

yes

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23
Q

are hypervariable regions also known as CDRs?

A

yes

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24
Q

what are CDRs flanked by?

A

less variable framework regions

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25
what determines the final antigen specificity on an antibody?
both heavy chains and light chain CDRs
26
can new antigen binding sites be formed by different combinations of heavy and light chain V regions?
yes
27
does every amino acid in the hyper variable region (HV) associate with antigen?
no
28
what creates a stable interaction between antigen and antibody?
multiple weak, non-covalent interactions between the two which are spread out over the six CDRs
29
where do B cells develop?
in the bone marrow
30
what do B cells differentiate into after encountering an antigen after they left the bone marrow?
plasma cells
31
what do plasma cells secrete?
IgM antibodies
32
what is agammaglobulinemia?
an inability to make antibodies
33
do the subclasses of antibodies have different characteristics, locations and functions?
yes
34
what antibody subclass makes up 80% of Lg present in blood?
IgG
35
why is IgG useful in passive immunization?
because it has a long half life (23 days)
36
why is the flexibility of IgG crucial for its function?
because It allows it to bind to multiple molecules at a time -has the ability to Wag, bend the elbow, Wave, and rotate
37
what does the wagging tail allow for on IgG molecules?
it allows for it to bind and activate complement Cq1
38
what antibody is produced first and what is the major antibody produced during secondary antibody response?
-IgM -IgG
39
what antibody makes up 5 to 10% of the antibodies in the blood?
IgM
40
what is the half life of IgM?
5 days
41
what type of IgM is expressed on the surface of B cells?
monomeric IgM
42
what shape is the IgM in its secreted from?
-it is a pentamer held together by disulfide bonds and a J chain (joining chain)
43
during pentamer formation does each successive joining of an IgM require a J chain which is then discarded except for the last one?
yes
44
what is the first class of antibody to be secreted during the primary antibody response?
IgM
45
how does IgM activate the classical complement pathway?
1. pentameric IgM molecules bind to antigens on the bacterial surface and adopt the staple form 2. C1q binds to one bound IgM molecule 3. binding of C1q to Ig activates C1r, which cleaves and activates the serine protease C1s (which would bind to CRP in the classical pathway)
46
how does IgG activate the classical complement pathway?
1. IgG molecules bind to antigens on the bacterial surface 2. C1q binds to at least two IgG molecules 3. binding of C1q to Ig activates C1r, which cleaves and activates the serine protease C1s (which would bind to CRP in the classical pathway)
47
where is IgA found?
in secretions like milk, saliva, tears, respiratory, and intestinal
48
what is the shape of IgA in the bloodstream?
it is a four chain monomer
49
does IgA have a known function?
no
50
what is the shape of IgA in secretions?
it is a eight chain dimer/trimer/tetramer held together by a J chain
51
what does the secretory component protect IgA from?
proteolysis
52
what are the two subclasses of IgA?
IgA1 and IgA2
53
where is IgA synthesized?
in plasma cells just below the epithelial membrane of the gut
54
what type of vesicle movement moves IgA across the cell to the apical surface?
transcytosis
55
what is the major role of IgE?
the elimination of parasites
56
if the half life of LgE antibodies are only 2 days, how do they have long lives?
because the Fc region binds with high affinity to mast cells and basophil cell Fc receptors, making it so they are passively aquired antigen receptors that live on
57
what are the main antibodies to "inappropriate" antigens?
IgE
58
what is a monoclonal antibody and a polyclonal antibody?
monoclonal antibodies = made from a cloned B cell, recognize one epitope polyclonal antibodies: made from multiple B cell clones, recognize multiple different epitopes
59
what are the 4 types of monoclonal antibodies?
-mouse -chimeric: mouse region is replaced by human constant region -humanized: only CDR loops are of mouse origin -human
60
does the antigen have to be close enough to the antibody so the epitope fits into the CDR of the antibody?
yes
61
is antigen-antibody binding reversible?
yes
62
what reverses antigen-antibody binding?
extreme pH, high salt concentrations, chaotropic ions (interfere with hydrogen bonding)
63
what is affinity?
-the strength of binding of an antigen to an antigen binding site
64
what is avidity?
-total binding strength of an antibody (one antibody binding to two epitopes increases overall affinity)

mbb 326 (6 decks)

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