ANTIBODIES Flashcards
Glycoproteins that recognize and bind to a particular antigen
with very high specificity
Antibodies
Antigen Binding sites
Epitope
(antibody binding site)
Paratope
What group of serum proteins does antibodies belong to?
Immunoglobulins
Where do immunoglobulins appear primarily?
Gamma band
At what band is Albumin found?
Alpha bond
At what bond is immunoglobulins found?
Gamma band
spleen is the primarily organ where the antigens
are destroyed
Reticular Endothelial system
postulated that certain cells had specific surface
receptors for antigen
Paul Ehrlich
• Occurred once antigen was introduced, it would select the cell
with proper receptor, combination would take place and
receptors would break off and enter the circulation as
antibody molecules
• New receptors would form in place of those broken off and
enter the circulation as antibody molecules
EHRLICH’S SIDE-CHAIN THEORY (SPECIFIC RECEPTOR)
Who postulates the Template theory?
Felix Haurowitz
• Antibody producing cells are capable of synthesizing a
generalized type of antibody and when contact with an
antigen occurs, the antigen serves as a mold or template and
alters protein synthesis so that antibody with specific fits is
made
• This now specific antibody enters the circulation, while the
antigen remains behind to direct further synthesis or
degradation to make more antibodies.
Template theory
Most accepted theory for antibody diversity. The key premise is that individual lymphocytes are
genetically programmed to produce one type of
immunoglobulin and that a specific antigen finds or selects
those particular cells capable of responding to it, causing it to proliferate.
Clonal selection
They independently supported
the idea of clonal selection process for antibody formation.
Niels Jerne and Mcfarlane Burnet
Which cell produces the antibody?
B-cells
How many polypeptide chains does an antibody contain?
4
They worked on Immunoglobulin G (IgG)
Gerald Edelman and Rodney Porter
A flexible Y-shaped molecule with four protein chains
Monomer
two sections at the end of Y’s arm. Contains also the antigen
binding sites (Fab) or the paratope. The Fab is identical on
the same antibody, but vary from one antibody to another.
Variable region
The number of binding sites = _________________?
the number of valences
• Stem of monomer and lower parts of Y arms
• Responsible for the type and antigen-antibody reaction that
occurs
• Constant region of heavy chain differs from one antibody
class to the other
• Structure serves as a basis for distinguishing the 5 different
classes: IgG, IgA, IgM, IgD and IgE
Constant region
• All of the antibodies have the same Fc region
• Mainly the one attached to the B cells or T cells
• For complement fixation, skin fixation and placental transfer
• No capability to bind the antibody
FC (FRAGMENT CONSTANT) REGION
FC region is for?
complement fixation, skin fixation and placental transfer
• First approximately 110 amino acids at the amino-terminal
end
• The remaining amino acids can typically be divided up into
two or three or more constant regions with very similar
constant regions with very similar sequences, designated CH1,
CH2, and CH3 (constant heavy chain 1,2,3)
Variable domain (heavy chain)
Constant regions of the H chain are unique to each class and
give each immunoglobulin
Constant region (heavy chain)
Refers to the heavy chain that determine the Ig class
Isotype
Minor variations of these sequences that are present in some individuals but not others
Allotype
• The aminoterminal ends of both L and H contain these
regions, which are essential to the formation of the antigen-
binding site
• variable portions of each chain are unique to a specific
antibody molecule.
Idiotype
Possess both constant and variable regions, it is the same for
all immunoglobulins
Light chain
Kappa: contains _____ of the Ig
Lambda: contains _____ of the Ig
65%
35%
How is Lambda and Kappa discovered?
produced by a malignant plasma cell from the urine of
Multiple Myeloma patients
At what temperature is bence jones proteins gonna precipitate?
60°C
Further heating of bence jones at 80 C, the precipitate will _______
Redissolve
• Connect heavy chains and heavy chains
• Connect heavy chains and light chains
• Connect light chains and light chains
Disulfide bond
Where is the hinge region found?
CH1 and CH2
Hinge region is also known as?
Flexible region
What causes the flexibility of the hinge region?
Proline
What is the other form of IgA?
Secretory IgA.m
In one immunoglobulin, it contains ____ domains
6
antigen binding site known also as the paratope
Fab site
CH2 and CH3, where B cells, T cells and
complement bind to
Fc region
• mainly done to study the immunoglobulins
• In order to fragment the immunoglobulins, we are going to
use enzymes
Fragmentation of monomer
Cleaves the Ig above the hinge region
Papain digestion
How many fragments of a monomer will Papain digestion give?
3 = 2 Fab and 1 Fc region
Cleaves the Ig below the hinge region
Pepsin digestion
How many fragments dk pepsin digestion give?
2 = F(ab)2 + Fc
This is the basic Ig structure?
Monomer
What are the Immunoglobulins that are monomer?
IgG, IgD, IgE, IgA
How many binding sites are there in a monomer, dimer and polymer?
M: 2
D: 4
P: 10
• Secretory component/ piece of IgA/ another class of IgA
• Prevents the enzymatic degeneration of enzyme among
secretions
• With J chain- additional structure, also known as joining
chain
Dimer
• >2 monomer
• IgM- pentamer
• 10 valence- 10 binding sites
• With J chain
Polymer
• Predominant type of immunoglobulin in humans
• Longest half-life of any immunoglobulin class
o Also known as the secondary antibody in terms of
infection
IgG
the next antibody after IgM. It is the one
usually being tested in the laboratory, the presence if
IgG means that there is already a lifelong protection to
a particular disease/ infection
Secondary
What IgG type is predominant?
IgG1
How many disulfide bonds do IgG1, 2, 3, and 4 have?
1 = 2
2 = 4
3 = 15
4 = 2
What is the most efficient subclass?
IgG1
What are the functions of IgG?
Provides immunity to the newborn by crossing through the
placenta
Fixes complement
Opsonization
Neutralization of toxins and viruses
Participation in agglutination and precipitation reaction
Decreased level of IgG can be manifested in?
primary (genetic)
or secondary (acquired) Ig deficiencies.
Significant increases of IgG are seen in the following
conditions:
Infectious diseases
Hematologic disorders
Collagen disorders
expressed as membrane-bound
antibody on B cells
Monomeric IgM
joining chain, Seen mostly in serum
Pentameric IgM
What is the appearance of IgM in free state?
star-like appearance
What is the appearance of IgM when combined with Ag?
Crab-like appearance
IgM is also known as?
Macroglobulin
What immunoglobulin do newborns produce?
IgM
Most primitive, first to appear among infants
IgM
IgM is Formed in response to stimulus specifically by?
gram-negative bacteria
In terms of infections, it will be the first one to increase
IgM
If IgM only is present = ___________
If there is no reaction from the IgM and positive for
IgG = _________
Acute infection
Chronic infection
First one to appear in phylogeny and the last to leave in
senescence
IgM
first test
for syphilis), heterophile antibodies, RF (rheumatoid factor),
cold agglutinins and allohemagglutinins belong under this
type of antibody.
Wasserman test
What are the functions of IgM?
Complement fixation
Best agglunitin
Opsonization
Neutralization of toxins
10-15% serum immunoglobulin
IgA
Monomeric in serum:
Occurs as a dimer in secretions:
IgA1
IgA2
• Prevents attachment of pathogen to mucosal surface
• Prevent enzymatic degradation if IgA
• Secretary component will serve as a specific receptor for IgA
Mucosal Immunity
responsible for immunoregulation
IgD
Where is IgD found?
unstimulated but immunocompetent B cell
Postulated as anti-idiotypic antibody involved in a feedback mechanism to switch off B-cells
IgD
Where is the location of IgD?
on the surface of a B lymphocyte in association with IgM
Least abundant immunoglobulin in the serum
IgE
Heat-labile antibodies, originally called as ______________?
Reagin antibody
Binds strongly to a receptor on mast cells and basophils and
together with antigen, mediates the release of histamine and
heparin from these cells
IgE
What is the most important function of IgE?
Mediates hypersensitivity
reactions, such as allergies, and anaphylaxis, and generally
responsible for an individual’s immunity to invading
parasites
___________ recognizes the IgE attached to parasite to release
Major basic protein and Eosinophil Cationic Protein
Eosinophil
