Feb. 14th (Exam 2) Flashcards
How are the different isotypes of immunoglobulins characterized?
By their constant region
What are the three things that vary between the isotypes?
- Hinge region
- Heavy chain length
- Carb binding
What are the 5 different classes of immunoglobulins as defined by the isotypes of the heavy chains?
- IgG (γ)
- IgM (μ)
- IgD (δ)
- IgA (α)
- IgE (ε)
What are the two light chain isotypes?
- Kamma (κ)
- Lambda (λ)
What are the functional differences between the two light chain isotypes?
Can one Ig have both types of light chains?
There has not been any functional difference found, and all the isotypes of heavy chains will bind to either light chain isotype.
Each Ig can only have one type of light chain isotype.
What is an immunoglobulin domain?
This is a single stable motif of about 100-110 amino acids
*on either the light and heavy chains that folds up into a compact and exceptionally stable protein domain.
What is the variable domain?
This is the domain that is present at the amino terminal end of each light or heavy chain
What is the antigen binding site created by?
- Variable Heavy domain
- Variable Light domain
What is the constant domain of the light chain?
This is always a single domain per light chain
Describe the constant domains of the various heavy chains.
What isotypes have three constant domains?
Four?
Can consist of 3 or 4 constant domains depending on the isotype.
Three constant domains: IgG, IgD, IgA
Four constant domains: IgM, IgE
Describe a single immunological domain and how it is held together generally.
Resembles a bulging sandwich of two Beta sheets that are held together by strong hydrophobic interactions of their side chains as well as a disulfide bond.
Adjacent strands within the beta sheet are connected by loops.
What are the hypervariable regions?
These are the regions of the variable regions that have extreme amino acid variability.
What is another name for the hypervariable regions regarding the binding that will happen to an epitope?
How many are there for each domain?
What type of protein structure do they always display?
We call these areas the Complementary Determining Regions (CDRs)
There are three per variable domain.
Loops
What is the rest of the variable domain that does not display such amino acid variability called?
Framework regions
What is an epitope?
What are epitopes usually made of?
This is the part of the antigen to which the antibody binds.
Carbohydrate or protein.
What is it called when an antigen contains more than one type of epitope or more than one of the same epitope?
When this is the case, we call it multivalent.
What are the two types of protein epitopes? Describe them.
Linear - these contain successive amino acids in a sequence
Discontinuous - these have amino acids that are brought together through complex folding
What type of chemical interactions are utilized in antibody-antigen interaction?
All non-covalent
- electrostatic forces
- hydrogen bonds
- van der Waals forces
- hydrophobic interactions
Define affinity as it relates to antigen-antigen binding site interaction.
Affinity is the binding strength of one epitope to an antigen binding site (there are two per antibody)
Why would two different antibodies that recognize the same epitope have different affinities?
Because there are small differences in the shapes and chemical properties of the antibodies.
What is avidity?
In what classes of antibodies is this term relevant?
This is the overall binding strength of multiple epitopes of an antigen
IgM pentametric 10 antigen binding sites
IgA 4 antigen binding sites
Explain, in detail, how monoclonal antibodies are made, as well as what they are.
In the explanation define:
- Myeloma cell
- Monoclonal antibodies
B-cells from an animal that is immunized with a particular antigen, usually a mouse, are isolated and fused with a myeloma cell.
Myeloma cell: cancerous plasma cell
The many different hybrid cells are then grown in a drug containing medium to kill off B-cells/Myeloma cells that did not fuse.
Then the individual hybrid cells are separated and the fused cells that are making the desired antibodies are identified and selected for future propagation.
Monoclonal Antibody: the antibodies that are made from one hybrid cell line - these are identical antibodies.
How does flow cytometry work?
Explain how to read the quadrant graph.
In the process of flow cytometry, we tag specific antibodies that are made in mice, specifically for human cell surface receptors, with fluorescence and are passed through the cytometer in droplets so they are singled out.
As they pass through a laser shoots at the cell, emitting a certain wavelengths.
The quadrant graph shows data collected for each individual cell.
Horizontal axis is for one type of cell receptor and how the various cells bound to the antibody that was tagged, either not at all (bottom left) or a lot (bottom right).
The vertical axis is for the other type of cell receptor and how the various cells bound to the antibody that was tagged, either a lot (top left) or not at all (top right).
Describe a chimeric monoclonal antibody.
This is the C region of a human antibody fused with the V region of mice antibodies.