Immunology 2 (Kyle) Flashcards
1. Describe the basic structure of antibody molecules 2. Distinguish the structural difference between isotypes of an antibody 3. Catalog the functional difference between isotypes of an antibody 4. Recognize the characteristics of epitopes
What is an antibody?
Antibodies are identical to what? (On the surface of the Bcell that secreted it)
Antibodies (Ab) are globular proteins (immunoglobulins) that are produced by B Cells. Ab’s are the primary component of humoral immunity
The B Cell receptor.
What do antibodies bind to?
Ab’s bind to antigens and interact with the host system and cells to promote clearance of infectious agents.
What is the main component of B cell surface receptors?
What is an immunoglobulin that is secreted from a B cell?
Membrane integrated forms of Ab molecules
An antibody
What is the common structure of an antibody?
All Ab’s consist of a common core of two identical light chains (24 Kd) and two identical heavy chains (55 or 70 kD)
How are the heavy chains and light chains connected?
One of the two light chains is attached to each heavy chain, and the heacy chains are attached to each other. These attachments are formed by intrachain disulfide bonds.
Are the heavy and light chains transcribed from the same genes?
NO Heavy and light chains are encoded on different genes.
What are the similar (But not identical) regions of the heavy and light chains?
Immunoglobulin domains (Ig domains)
How are Ig domains formed and what are the regions within the Ig domains?
IG domains fold independently are are formed from disulfide bonds. The animo-terminal Ig domain of each chain is the VARIABLE region ( V- region ) and is highly variable between Ab molecules. The CONSTANT region ( C-region) is conserved throughout many Ab molecules.
Where do Ab molecules perform their function?
In the extracellular space in the presence of an infection.
What allows Ab molecules to withstand the variations in Ph, Salt conc, and proteolytic enzymes that are encountered in the extracellular space?
Their unique 3 degree structure.
What is the primary difference between the C and V domains of the immunoglobin molecule?
V domain is larger and contains an extra loop of polypeptide chain.
What forms the antigen binding domain?
The localized region of both heavy and light chain V domains form the antigen-binding site of each “arm” of an antibody molecule.
What is similar about the C and V domains?
Both the C and V domains are roughly cylindrical shape and are formed by two adjacent B-Sheets structures that are covalently linked by a disulfide bonds.
What forms immunoglobulin folds?
The adjacent B-Sheets in the C and V domains.
What is a hypervariable region?
Hypervairable regions are three distinct regions in the V chains of an Ab molecule designated HV1, HV2, and HV3. They are formed from the loops between B-Sheets and form the ANTIGEN BINDING SITES
What is a framework region?
A framework region is a low variable region between the hypervariable regions.
What do framework regions actually do?
The framework region of both the heavy and light chains from the B-Sheets that provide the structural framework of the domains.
What is the function of the Ab molecule?
The function of Ab’s is to bind to microorganisms and facilitate their destruction and removal from the body/
What is an EPITOPE?
The portion of any particular antigen that an antibody binds to is called an antigenic determinant or and EPITOPE
Complex macromolecules typically have multiple epitopes each of which can be bound by a separate antibody molecule, such molecules are called…?
Multivalent antigens
What chemical forces bind an Ab molecule to an antigen?
Noncovalent forces
The antigen-binding region of an Ab molecule is normally rich in what type of AA?
Aromatic
What determines how long an Ab stays bound to an antigen?
Binding affinity
What are the two types of antigenic determinants that antibodies can bind?
Continuous epitopes- formed by a linear structure of amino acids.
Discontinuous epitopes- Formed by AA from different parts of the protein brought together via protein folding.
What aspect of antibody structure allows them to be divided into five isotypes?
Isotypes of antibodies are determined by the structure of the heavy chain.