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Avidity
HND Immunology
Question | Answer |
---|---|
Why are most antigen known as being multivalent? | Because they have multiple epitopes. |
What does the serum produced upon exposure to an antigen contain? | Many different antibodies against many different epitopes. |
Will each pairing between antibody and antigen have the same affinity? | No, each pairing will have a different affinity. |
Can individual affinities be measured in the antiserum? | No, individual affinities can not be measured. |
Define avidity. | The total binding strength between the antiserum and antigen. |
What is the relation between avidity and affinity? | Avidity is always greater than the total sum of affinities. |
What can be done with multi-valent antigens? | They can be linked together by two or more antibody molecules. |
What happens if one antibody dissociates from the multivalent antigen and antibody complex? | The cross-linkage can be maintained by the remaining antibodies until another antibody replaces the dissociated one. |
Why is avidity known as a dynamic situation? | Because some antibodies are dissociating and others are re-associating all the time. |
What is the linking of multi-valent antigens known as? | Cross-linking. |
What is cross-linking crucial for? | The activation of B cells and the compliment system. |
What is meant by valency? | The maximum number of epitopes an immunoglobulin can react with. |
What determines the valency of an immunoglobulin? | The number of Fab regions present on the immunoglobulin. |
What is the valency of IgG? | 2. |
What is the valency of IgD? | 2. |
What is the valency of IgE? | 2. |
What is the valency of IgA? | 2 in its monomeric serum form. 4 in its dimeric secretory form. |
What is the valency of IgM? | 2 in its monomeric form as a B cell receptor. 10 in its pentameric free floating antibody form. |
What leads to increased avidity? | More antigen binding sites, which lead to more binds, meaning less dissociation and greater avidity. |