Antigen Binding Flashcards
(29 cards)
What part of the antibody determines specificity for antigens?
The variable (V) regions of the heavy and light chains, especially the hypervariable regions (CDRs).
What is cross-reactivity in antibody responses?
When an antibody made for one antigen also binds a different but structurally similar antigen.
Why is high specificity in antibodies important?
To prevent antibodies from reacting with self molecules or unrelated antigens, reducing risk of autoimmunity.
How is antibody diversity generated?
By random recombination of V(D)J gene segments and nucleotide additions during recombination.
What is the antibody repertoire?
The total collection of antibodies with different specificities in an individual.
Which cells are responsible for generating antibody diversity?
B lymphocytes, through mechanisms like V(D)J recombination and junctional diversity.
What is affinity in antibody-antigen binding?
The strength of binding between a single antigen-binding site and an epitope.
What is avidity?
The overall strength of binding between an antibody and a multivalent antigen, combining multiple affinities.
How does IgG achieve bivalent binding?
By using both its antigen-binding sites to engage with epitopes spaced appropriately.
Why does IgM have high avidity?
Because it has 10 identical antigen-binding sites that can bind simultaneously to multivalent antigens.
What is the ‘zone of equivalence’ in antigen-antibody interactions?
The point at which antigen and antibody concentrations are optimal for forming large immune complexes.
What happens when antigen is in excess?
Smaller immune complexes form, reducing immune effectiveness.
What can large immune complexes cause?
They can deposit in tissues like kidneys and joints, causing immune complex diseases.
What is affinity maturation?
The process by which B cells produce antibodies with increased affinity for an antigen during immune responses.
What causes the changes in antibody affinity during affinity maturation?
Somatic hypermutation of V region genes in activated B cells.
How are high-affinity B cells selected during an immune response?
They bind antigen more effectively and are preferentially selected to proliferate.
How does the dissociation constant (Kd) change with affinity maturation?
It decreases, indicating stronger binding (e.g., from 10⁻⁷ M to 10⁻¹¹ M).
What structural change allows B cells to secrete antibodies instead of expressing them on the surface?
A switch from membrane-bound to secreted forms by altering the C-terminal tail of the heavy chain.
What is isotype switching?
A change in the constant (C) region of the antibody heavy chain without altering the variable region.
Does isotype switching affect antigen specificity?
No, it only changes the antibody’s effector functions.
What does Figure 5.14 illustrate?
Valency and avidity in antibody-antigen interactions, showing how epitope spacing affects binding.
What does Figure 5.15 show about immune complexes?
Their size depends on relative concentrations of antigen and antibody.
What does Figure 5.16 demonstrate?
Structural changes in antibodies during humoral responses, including affinity maturation and isotype switching.
How do antibody structure and function relate?
The V region provides specificity for antigens; the C region determines effector function.
