Antibody 1 Flashcards
What are the two types of epitopes?
B and T cell
How does the antigen interact w a B-cell?
Membrane Ig and antigen
How does the antigen interact w a T-cell?
Membrane TCR, antigen, MHC
Which type of cell can detect soluble antigen?
B-cells
What additional molecules does a B-cell need to see antigen?
None
What additional molecules does a T-cell need to see antigen?
MHC, CD8/CD4
Chemical nature of antigen for B-cells
Protein, lipid, polysaccharide
Chemical nature of antigen for T-cells
Protein
The epitopes of B-cells can be what 4 forms?
- Accessible (topographical)
- Hydrophilic
- Mobile
- Sequential or conformational
What epitopes of T-cells can be what 3 forms?
- Accessible or internal
- Linear
- Amphipathic
Ag-Ab interactions involve what type of binding between molecules?
Highly specific and reversible
What type of interaction do Ag and Ab have?
On off on off
Stick and fall apart
What type of bond is Ag and Ab not?
Covalent
How is the specificity determined in a Ag-Ab bond?
Determined by multiple low affinity non-covalent bonds that require a specific fit
What type of bonds do Ag-Ab have? (4)
- Ionic (electrostatic)
- Hydrogen Bonds
- van der Waals interations
- Hydrophobic bonds
How many binding sites does affinity deal with?
One
What is affinity?
The strength of the sum of non-covalent interactions b/w a single Ag binding site on an Ab and a single epitope
How well one antibody stick to a single epitope of an Ag
What is Ka?
Association constant
What is the formula for affinity?
[Ab-Ag}/[Ab][Ag]
Compound/free Ag and free Ab
What does a low affinity mean?
Falls apart (lower #)
What does a high affinity mean?
Stuck together (higher #)
Avidity?
The strength of multiple interactions b/w multivalent antibody and antigen
How can we compensate weak bonds?
Avidity
More bonds
How can we compensate for low affinity?
High avidity
Affinity
The stregth of binding between a single Ag epitobe and an Ab
What is affinity dictated by?
The Ag-Ab fit
Avidity
The function of the combined strength of binding affinity and the Ab/Ag valency
What is avidity dictated by?
Affinity and the number of Ag/Ab bindings
What is the measure of how many hands you have on the monkey bars?
Avidity
What are two possible cross-reactivity of antigens?
- Different antigens may share common epitopes
2. Epitope of an antigen may be different but share common chemical properties
What happens if different Ag share common epitopes?
Ab will bind both
What happens if an epitope is different but may share common chemical properties?
Ab will bind 2 diff epitopes
Two cross reactions
Shared epitopes
SImilar chemical
What is an example of cross reactivity?
ABO blood
What antibodies do you have if you have boold type A?
Antibodies to blood type B
What antigens do blood type A have?
A antigen
What antibodies fo blood type B have?
A antibodies
What antibodies do AB have? Antigens?
No antibodies
A and B antigens
What blood type has no antigens?
O
Anti-A antibodies originate from
Influenza virus
Anti-B antibodies
Glycoproteins or Gram-negative bacteria
What happens if you get the wrong blood?
Precipitation occurs (clumps)
How does precipitation occur?
When Ag-Ab interactions result in the formation of a lttice structure
What does a lattice formation require?
Bivalent Ab and at least a bivalent or polyvalent Ag
How can we measure precipitin reactions?
By adding an increased amount of antigen to a fixed amount of Ab
What inhibits precipitation?
Excess of either Ab or Ab
In the zone of equivalence is the conc. of Ag and Ab equal?
No
What is the zone of equivalence?
Optimal conc of Ab and Ag (not equal)
What does the zone of equivalence give us?
The dilution factor
What theory did Paul Ehrlich put forth?
Side chain thoery
SIde chain theory
Antibody producy cells express multiple side chians w various antigen specificities
Once engaged with antigen what happened ?
Engagement with Ag results in the production and secretion of many more identical Ag specific side chains
What is the issue with the side chain theory?
The Ig gene locus would need to be 35x bigger than the entire genome
Instructional theory
The Ag serves as a template and the Ig molecule folds and mutates around it
How many genes are needed in the instructional theory?
Few genes bc a single molecule could assume many specificities
What type of Ig molecule do you need in the instructional theory?
Generic Ig
it folds around the Ag
What is the problem instructional theory?
It does not account for the pre-existing specificity we have
What theory came after the side-chain theory?
Instructional
What theory followed the instructional theory?
Two gene theory
