Antibody Flashcards
They are produced by B lymphocytes (plasma cells) in response to exposure to foreign substances, called antigens.
ANTIBODY
are glycoproteins that play a crucial role in the humoral immune response.
ANTIBODY
Antibody aka
Immunoglobulins
ANTIBODY
FUNCTIONS
Neutralization
Opsonization
Complement Activation
Antibody-dependent cell-mediated
Cytotoxicity (ADCC)
Antibodies are…
created by the immune system to target foreign invaders in the body, like a bacteria or virus.
Antibodies prevent a virus or toxic protein from binding their target.
Neutralization
Neutralization
Antibodies prevent a virus or toxic protein from binding their target.
A pathogen tagged by antibodies is consumed by a macrophage or neutrophil.
Opsonization
Antibodies attached to the surface of a pathogen cell activate the complement system.
Complement activation
ANTIBODY PROPERTIES
• Protein in nature
• With high molecular weight
• Present in serum/plasma, saliva, semen, CSF, and other body fluids
ANTIBODY
STRUCTURE
The fundamental unit of an antibody is a________, composed of two identical_________ and_______ linked by________(Hinge region).
tetrapeptide
heavy (H) chains and two identical light
(L) chains
disulfide bonds
Immunoglobulin genes are found in:
Chromosome 14:
Chromosome 2:
Chromosome 22:
Heavy chain genes
kappa chain genes
epsilon chain
Bence-Jones Proteins
Discovered by….
Dr. Henry Bence Jones
Bence-Jones proteins
Monoclonal immunoglobulin light chains that are found in the urine of patients with_______
Multiple Myeloma
Heat solubility test
BJPs precipitate at_____ to_____, dissolve at______, and reappear upon cooling
60°C to 70°C
100°C
Bence-Jones protein
Types:
Kappa (к) light chains (60%)
Lambda (2) light chains (40%)
Variable Region
The _________end of both the heavy and light chains.
This region is unique to each antibody and determines its_______ for a particular antigen.
Forms the ______site.
amino-terminal
specificity
antigen-binding
The amino-terminal end of both the heavy and light chains.
This region is unique to each antibody and determines its specificity for a particular antigen.
Forms the antigen-binding site.
Variable Region
Constant Region
The _______end of the heavy chains.
This region is responsible for binding to_______ cells and molecules of the immune system.
carboxy-terminal
effector cells
The carboxy-terminal end of the heavy chains.
This region is responsible for binding to effector cells and molecules of the immune system.
Constant Region
• Composed of one light chain and one-half of a heavy chain linked by disulfide bonds.
Fragment antigen-binding (Fab)
Primary function: of the Fab region is
antigen recognition and binding
Fab region
Specificity is due to…
hypervariable regions
The carboxy-terminal end of the heavy chains.
This region is responsible for binding to effector cells and molecules of the immune system.
Fragment crystallizable (Fc)
Fragment crystallizable (Fc)
The ______end of the heavy chains.
This region is responsible for binding to ______ and ______of the immune system.
carboxy-terminal
effector cells and molecules
Fragment crystallizable (Fc)
Composition:
two heavy chains, held together by disulfide bonds.
Fc region
Mediates the antibody’s effector functions
Complement activation
Opsonization
ADCC
IMMUNOGLOBULIN VARIANTS
ISOTYPES
ALLOTYPE
IDIOTYPE
For example, the isotype determines whether an antibody belongs to….
IgG, IgM, IgA, IgD, or IgE class.
These determinants are associated with the constant region of the heavy chain and define the different immunoglobulin classes and subclasses.
ISOTYPES
The primary type of antigenic determinant present on the
immunoglobulins of all members of a particular species.
ISOTYPES
An example of an_______ is the Gm specificity found on the heavy chain of IgG molecules.
Allotype
are subtle genetic variations within the constant regions of heavy and light chains, resulting in minor amino acid sequence differences between individuals.
ALLOTYPE
• These variations in the antigen-binding site are responsible for the specificity of each antibody for a particular antigen.
IDIOTYPE
• Unique to each individual antibody molecule and are formed by variations in the variable regions of both heavy and light chains.
IDIOTYPE
Pentamer
5 identical units of Y-shaped antibodies
10 antigen-binding sites
IgM
IgM Linked by
J-chains
• The first antibody produced by the body when encountering a new infection (primary/initial immune response)
IgM
IgM
The most efficient immunoglobulin at:
activating the classical complement pathway
clumping together antigens (agglutination)
Four subclasses of IgG:
IgG1, IgG2, IgG3, and IgG4.
Most abundant/prevalent antibody in serum
IMMUNOGLOBULIN G (IgG)
The only antibody isotype that can cross the placenta
• Except_____
IMMUNOGLOBULIN G (IgG)
IgG2
Has the longest half-life (~______)
IgG
23 days
Predominant antibody during secondary (anamnestic) immune response
IgG
IgG
Most efficient in:
Neutralization
Opsonization
ADCC
Precipitation
Can bind to mast cells or basophils and trigger these cells to release histamine and Fab region other inflammatory mediators.
IMMUNOGLOBULIN E (IgE)
• a unique antibody with a specialized role in allergic responses and defense against parasites.
IMMUNOGLOBULIN E (IgE)
iMMUNOGLOBULIN A (IgA)
• Exists as
both a monomer and dimer
Mainly circulates in the serum
• Act as an anti-inflammatory agent
IgA1 (Monomer)
• IgA1 (Monomer)
Mainly circulates in the_____
• Act as an______
serum
anti-inflammatory agent
• Has a secretory component that protects it from being broken down by gastrointestinal proteolytic enzymes
IgA2 (Dimer)
• Predominant immunoglobulin in mucosal secretions
IgA2(Dimer)
• IgA2 (Dimer)
• Predominant immunoglobulin in______
• Has a______ that protects it from being broken down by gastrointestinal proteolytic enzymes
mucosal secretions
secretory component
• It is the second type of immunoglobulin to Fab region appear on B cells
IMMUNOGLOBULIN D (IgD)
• Most IgD is found on the surface of…
immunocompetent, unstimulated
B lymphocytes alongside IgM.
essential for the development of a highly specific and adaptable humoral immune response
CLASS SWITCHING
• A biological process that allows B cells to change the class of antibody they produce while maintaining their antigen specificity
CLASS SWITCHING
Mechanism of CLASS SWITCHING
Mechanism:
Initial IgM production
Activated T-helper cells release cytokines that signal B cells to undergo class-switching
Gene rearrangement (class switch
recombination)
Production of new antibody isotype
CLASS SWITCHING
Mechanism:
Initial_________
_______release______ that signal _____to undergo class-switching
_______(class switch
recombination)
Production of______
IgM production
Activated T-helper cells; cytokines; B cells
Gene rearrangement
new antibody isotype
AFFINITY vS. AVIDITY
Affinity:
Avidity:
AFFINITY: the initial force of attraction that exists between a single Fab site on an antibody molecule and a single epitope or determinant site on the corresponding antigen
AVIDITY: represents the overall strength of the bond between a multivalent antibody and a multivalent antigen.
the initial force of attraction that exists between a single Fab site on an antibody molecule and a single epitope or determinant site on the corresponding antigen
Affinity
represents the overall strength of the bond between a multivalent antibody and a multivalent antigen.
Avidity
AGGLUTINATION
” the clumping of particles with antigens on their surfaces
are more efficient at agglutination because their large size and multivalency permit more effective bridging of the space between cells caused by zeta potential
Immunoglobulin M (IgM) antibodies
” IgM is the most efficient of all immunoglobulins at triggering the classical complement pathway because a single molecule can initiate the reaction as a result of its multiple binding sites
COMPLEMENT FIXATION
• IgG antibodies can bind to specific
sites on toxins or viruses essential for their attachment to host cells.
NEUTRALIZATION
This prevents the pathogen or toxin from interacting with the host cell, effectively neutralizing its ability to cause infection or damage.
NEUTRALIZATION
Combination of soluble antigen with soluble antibody to produce visible insoluble complexes.
PRECIPITATION
These cells achieve this by recognizing and binding to the Fc portion of the antibodies attached to the target cells.
ANTIBODY-DEPENDENT
CELL CYTOTOXICITY (ADCC)
a process where “antibody-coated target cells” are destroyed by immune cells such as natural killer (NK) cells, monocytes, macrophages, and neutrophils.
ANTIBODY-DEPENDENT
CELL CYTOTOXICITY (ADCC)
ADCC
Antibodies bind receptors on target cell surface
Effector cell Fc-receptors recognize cell-bound antibodies
Effector cell lyses target cell
Target cell death
All the antibodies in a ______preparation are identical and originate from a single B cell lineage.
Monoclonal antibody
• Purified immunoglobulin produced by cells cloned from a single fusion-type hybridoma cell.
MONOCLONALANTIBODIES