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Chapter 5 Flashcards

1
Q

What are the two types of B cells?

A

Plasma cells (antibody secreting) and memory cells

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2
Q

Where does the collaboration of Ig with other B cell receptors being?

A

At the ER

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3
Q

What is another name for antibodies?

A

Immunoglobulins (Ig)— they are called globulins because of their globular structure — can be membrane bound or secreted

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4
Q

Membrane bound immunoglobulins

A

Membrane bound antibody is present on the surface of B cells where it serves as the antigen specific receptor

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5
Q

What heterodimer combines with the membrane bound form of antibody to form the BCR?

A

Igalpha/Igbeta

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6
Q

What are secreted antibodies produced by?

A

Plasma cells

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7
Q

What amino acids make up the hinge region of antibodies?

A

Cysteine and proline residues; The cysteines are involved in the formation of inter chain disulfide bonds, and the proline residues prevent folding in a globular structure.

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8
Q

What is the variable region of an antibody?

A

Constitutes the part of the molecule that binds to the antigen for which the antibody is specific

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9
Q

What is another name for the variable region?

A

CDRs—- complementary- determining region

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10
Q

How many isotypes of immunoglobulins are there?

A

5 types; IgG, IgM, IgD, IgA, IgE

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11
Q

What is one of the best immunoglobulins that can activate the complement system?

A

IgM

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12
Q

What gene encodes the constant region of IgM?

A

Cµ

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13
Q

What gene encodes the constant region of IgA?

A

Cα

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14
Q

What gene encodes the constant region of IgE?

A

CƐ

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15
Q

What is an idiotype?

A

A unique combination of amino acids in the light and heavy chains of antibody at the combining site of specific antibody

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16
Q

What is binding specificity dependent on?

A

Different amino acid sequences

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17
Q

Anti antibody idiotype

A

Antibody produced against a particular antigen– immunize mice with that antibody— that mouse will then produce antibody against that antibody

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18
Q

Anti antibody idiotype

A

Antibody produced against a particular antigen in a mouse– immunize other mouse with that antibody— that mouse will then produce antibody against that antibody– this is because the variation of epitope on the antibody acts as an antigen and acts to produce another antibody (Jerne’s Theory on Regulation and Immunization)— if that antigen goes to combining site, there is a competition ?????

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19
Q

What is allotypy?

A

It is based on genetic differences between individuals. In other words, different allelic forms of the heavy or light constant region genes give rise to different forms of the same gene at a given locus.

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20
Q

What are the two most important features of immunoglobins?

A

Specificity and biological activity

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21
Q

What does specificity mean?

A

It is attributed to a defined region of the antibody molecule containing the hypervariable region complementary- determining region (CDR). This restricts the antibody to combine only with those substances that contain a particular antigenic structure

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22
Q

What are the biological effects of antibodies?

A

Neutralization of toxins, immobilization of microorganisms, neutralization of viral activity, agglutination of microorganisms or of antigenic particles

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23
Q

What can the differences in various biological activities of antibodies be attributed to?

A

Structural properties conferred by the germline- encoded portions of the Ig molecule. Antibody molecules contain structural components that are shared with other antibodies within their class, and an antigen binding component that is unique to a given antibody

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24
Q

What are myeloma proteins?

A

Homogeneous immunoglobulins produced by the progeny of a single plasma cell that has become neoplastic in the malignant disease called multiple myeloma— isolation and characterization of immunoglobulins???? Ask Azghani

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25
What are Bence Jones proteins?
An aid to structural studies of antibodies, which are present in the urine. They are homogeneous proteins produced in large quantities in some patients with multiple myeloma.
26
What was discovered with papain digestion?
In England, in 1959, Porter found that proteolytic treatment with the enzyme papain split the immunoglobin molecule into three fragments of equal size. Two of the fragments were found to retain the antibody's ability to bind antigen specifically, but could no longer precipitate the antigen from solution. Referred to as Fab (fragment antigen binding). The third fragment was homogeneous and called the Fc fragment. It cannot bind antigen
27
What does mercaptoethanol do to antibody?
Breaks the molecule into 4 chains; two identical light chains and two identical heavy chains
28
What is the basic structure of antibodies?
Basic unit of 4 polypeptide chains, two identical heavy chains and two identical light chains held together by disulfide bonds
29
What are the immunoglobulin fold domains?
The heavy and light chains have intrachain disulfide bonds, which created antiparallel beta pleated sheet structure
30
What is the function of the hinge region?
Provides flexibility between the two Fab arms of the Y shaped antibody molecule. It allows the Fab arms to open and close to accommodate binding to two identical antigenic epitopes
31
Why are the sera or urine samples of patients with myeloma useful?
They contain copious amounts of immunoglobulin molecules, all identical in structure and specificity by virtue of their production by the neoplastic plasma cells causing the disease
32
Why are the sera or urine samples of patients with myeloma useful?
They contain copious amounts of immunoglobulin molecules, all identical in structure and specificity by virtue of their production by the neoplastic plasma cells causing the disease
33
What are the binding forces involved between an antigen and antibody?
Non covalent interactions such as Van der Waals, hydrogen bonding, electrostatic, hydrophobic interactions, so that means the antigen and antibody must become super close to allow a total binding force that is adequate for stable reaction
34
What is one thing that determines antibody specificity?
Different amino acid sequences in their hypervariable regions
35
What happens when antibodies with different amino acid sequences are specific for the same epitope?
They will have different binding affinities
36
What does redundancy mean?
A particular antibody combining site may have the ability to combine two or more apparently diverse epitopes. This is due to the size of the combining site on the antibody
37
Why are there several different effector mechanisms when a specific antigen binds with a specific antibody?
Because of the different classes of immunoglobulins or isotypes, which combine with the same epitope but each of which triggers different biologic response--- structural variations in constant regions of heavy chains
38
What is the predominant immunoglobulin in the blood, lymph, cerebrospinal, and peritoneal fluid?
IgG, with a molecular weight of 150,000 Da
39
What are the four subclsses of IgG?
IgG1, IgG2, IgG3, and IgG4
40
What is the half life of IgG?
23 days. Since it is so persistent (has the longest half life of all Igs), it is most suitable for passive immunization by transfer of antibodies
41
What happens to IgGs half life at high concentrations?
It is decreased
42
What is agglutination?
Clumping of particulate (insoluble) antigens such as microorganisms
43
Describe the FcRp receptor process
Circulating monomeric IgG plus antigen (immune complex) enters an antigen presenting cell through the process of endocytosis. Within the endosome, th complex binds FcRp; IgG and Ag dissociate allowing the IgG to be directed to the cell surface for recycling. Antigen undergoes lysosomal degradation (antigen processing), and its proteolytic fragments are ultimately expressed on the cell surface in the context of MHC class II molecules
44
Why is cross reactivity a good thing?
Because this means that antibodies do not have to be made for every single antigen
45
What immunoglobuins are apart of the BCR?
IgM and IgD
46
What are the biologic properties of IgG? (explained in more detail in notes!!)
Aggultination and Formation of Precipitate Passage through the placenta and absorption in neonates Opsonization Antibody dependent cell mediated cytotoxicity Activation of complement Neutralization of toxins Immobilization of bacteria Neutralization of viruses
47
Where is IgG found?
Distributed equally between the intravascular and extravascular spaces
48
Where is IgM found?
Predominantly in the intravascular spaces
49
What is the half life of IgG?
23 days
50
What is the half life of IgM?
5 days
51
What is the most efficient immunoglobulin as initiator of complement mediated lysis of microorganisms and other cells?
IgM
52
What is the first class of antibodies generated after immunization or infection?
IgM
53
What is the first isotype synthesized after immunization?
IgM
54
Which antibody can form macromolecular bridges between epitopes on molecules that may be too distant from each other to be bridged by smaller antibodies?
IgM
55
Which antibody is well suited for combining with antigens that contain repeated patterns of same antigenic determinant?
IgM
56
What are isohemagglutinins?
They are the naturally occurring antibodies against red blood cells antigens of the ABO blood groups
57
Which Ig is an isohemagglutinins?
IgM
58
Does IgM pass through the placenta?
NO
59
What is the shape of IgM?
It is a pentameric molecule composed of 5 immunoglobulins. The Fc portions are linked by a polypeptide chain termed the J chain.
60
How many Fab regions does IgM have?
You would think that there are 10 variable regions, however, there are only 5 because of conformational restraints imposed by the polymerization. Each Fab region cannot open fully with respect to the adjacent Fab.
61
What is the major Ig found in the external secretions such as saliva, mucus, sweat, gastric fluid, and tears?
IgA
62
What is the main Ig found in the colostrum of milk in nursing mothers and may provide the neonate with a major source of intestinal protection against pathogens during the first few weeks after birth?
IgA
63
Which Ig is of importance in the primary immunologic defense against local respiratory or gastrointestinal infections?
IgA
64
What is IgA's role in mucosal infections?
It prevents organisms from attaching to and penetrating epithelial surface of mucosal sites
65
Which Ig does not contain receptors for complement and thus cannot induce complement- mediated bacterial lysis?
IgA
66
What is IgA's bactericidal activity?
IgA has been shown to possess bactericidal activity against gram negative organisms, but only in the presence of lysozyme
67
What are the biological properties of IgA?
1. Role in mucosal infections 2. Bactericidal Activity 3. Antiviral activity
68
What is IgA's antiviral activity?
It prevents viruses from entering host cells. It also is an efficient agglutinating antibody
69
Which immunoglobulin is highly susceptible to proteolytic degradation?
IgD-- because of its hinge region
70
Which Ig is very low and variable amounts in the serum?
IgD
71
What is the purpose of IgD when co-expressed with IgM to form a BCR?
It serves as a marker of the differentiation of B cells to a more mature form
72
What is the major biological significance of IgD?
May be in silencing autoreactive B cells
73
Which two Igs have an extra Ch domain?
IgE and IgM
74
What is the half life of IgE?
2 days-- shortest half life of all Igs
75
Why is IgE so low in concentrations in the serum?
Because of its slow rate of synthesis and to the unique ability of the Fc portion containing two extra CH domain to bind with very high affinity to receptors found on mast cells and basophils. Once bound to these cells, IgE may be retained for weeks or months. Antigen can bind to the Fab regions of the Ig bound to another cell, which activates that cells, and it releases its contents into the cell (histamines, heparin) that mediate hypersensitivity reactions
76
Which Ig is neither an aggultinating or complement activating antibody?
IgE
77
What is IgE's role?
It has a role in protection against certain parasites such as helminths (worms), a protection achieved by activation of the same acute inflammatory response seen in a more pathologic form of immediate hypersensitivity responses
78
Describe the phases of the primary antibody response.
1. Latent or lag phase: After initial exposure to an antigen, a period of 1 to 2 weeks follows before antibody is detectable in the serum. 2. Exponential phase: During this phase, the concentration of antibody in the serum increases exponentially. 3. Steady state: During this period, production and degradation of antibody are balanced 4. Declining phase: Finally, the immune response begins to shut down, and the concentration of antibody in serum declines rapidlyq
79
What is the first class of antibody detected in primary responses?
Generally IgM
80
What cells are responsible for mounting a secondary response?
Memory cells
81
What is class switching?
Occurs during secondary response. There is a marked change in the type of antibody produced in the secondary response in the appearance of different classes of immunoglobulins with the same antigen specificity. Usually IgG becomes more concentrated in serum than IgM antibodies, which might disappear all together.

Immunology (5 decks)

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