39 Questions
What is the main function of the (Fab)2 fragment of an antibody?
Detect antigen
How do antibodies neutralize bacterial toxins and viruses?
By coating the bacterial toxins and virus particles
What is the role of antibodies in opsonization?
Coating an antigen to make it recognizable by phagocytes
Which component of an antibody initiates inflammatory and effector functions associated with cells?
Fc component
What is the main function of the Fc component of an antibody?
Initiate inflammatory and effector functions of complement
How do antibodies activate the complement system in relation to a bacterial cell?
By coating the bacterial cell
Which function is NOT associated with antibodies in host defense?
Causing the trafficking of antigens into the antigen processing pathways
In receptor-mediated endocytosis, what is the role of antibodies?
Coating an antigen for recognition by phagocytes
Which property of antibodies is crucial in rendering antigens recognizable as foreign by phagocytes?
(Fab) fragment coating effect
What is the MW of IgM in its pentameric form?
900,000 Da
What is the main function of IgG?
Activates the complement system
Which Ig is known for its ability to cross the placenta and be passed to newborns via colostrum?
IgG
What conformational change does IgM undergo when binding to antigen?
Staple or 'crab' conformation
Which Ig is most efficient for agglutinating antigen?
IgM
In which form does IgA exist in external secretions?
Dimer
'Secretory IgA' is primarily formed during what process?
'Transport through mucous membrane epithelial cells'
'Antibody-dependent cell-mediated cytotoxicity (ADCC)' is mediated by which cells?
'NK cells'
'Opsonizing antibody' primarily promotes which process?
'Phagocytosis'
'IgM' is the first Ig produced in the immune response and exists in what form?
'Pentameric molecule'
Which Ig antibody has the longest half-life of all Ig's and is the only class able to cross the placenta?
IgG
Which Ig antibody primarily mediates antibody-dependent cell-mediated cytotoxicity (ADCC)?
IgG
Which Ig antibody is known to exist in a pentameric form and is efficient at fixing complement?
IgM
In antigen-induced conformational changes, which conformation of IgM is efficient at fixing complement?
'Crab' conformation
Which Ig antibody is crucial in defense against local respiratory or gastrointestinal infections and possesses bactericidal activity?
IgA
What is the main function of the 'secretory component' in IgA dimers?
Prevention of epithelial attachment by pathogens
'Secretory IgA' is primarily formed during which process?
Transport through mucous membrane epithelial cells
'Opsonizing antibody' primarily promotes which process?
Phagocytosis of pathogens
'Antibody-dependent cell-mediated cytotoxicity (ADCC)' is mediated by which type of cells?
NK cells
Which Ig antibody is known to be an opsonizing antibody promoting phagocytosis?
IgG
Explain the process of receptor-mediated endocytosis involving dimeric IgA.
Dimeric IgA binds to a poly-Ig receptor on the basolateral membrane of an epithelial cell, internalizes, and after transport to the luminal surface, the poly-Ig receptor is enzymatically cleaved, releasing the secretory compound bound to the dimeric IgA.
What is the difference between antibody affinity and antibody avidity?
Antibody affinity is the binding strength at a single binding site, while antibody avidity is the overall strength of the antibody-antigen interaction taking into account multiple binding sites.
Why is the Fc region of an antibody important?
The Fc region of an antibody is crucial for effector functions like opsonization, complement activation, and antibody-dependent cell-mediated cytotoxicity (ADCC).
What is the primary function of IgE in the immune system?
IgE has the lowest concentration in serum and plays a role in hypersensitivity reactions (allergies) and protection against parasites through binding to mast cells and basophils.
How does antibody avidity compensate for low affinity?
High avidity, which incorporates the affinity of multiple binding sites, can compensate for low affinity by increasing the overall strength of the antibody-antigen interaction.
What is the function of IgD in the immune system?
IgD, co-expressed with IgM on mature B cells, is thought to be involved in the elimination of self-reactive B cells.
How does dimeric IgA reach the luminal surface of epithelial cells?
Dimeric IgA binds to a poly-Ig receptor on the basolateral membrane, is internalized by receptor-mediated endocytosis, and then transported to the luminal surface.
What is the significance of antibody affinity in binding to antigens?
Antibody affinity measures the binding strength at a single binding site, influencing the specificity and strength of the antibody-antigen interaction.
Explain the role of IgM in antibody-antigen interactions.
Secreted pentameric IgM has higher avidity than IgG, allowing it to efficiently bind to antigens and activate the complement system.
What is the function of the poly-Ig receptor in the process of receptor-mediated endocytosis?
The poly-Ig receptor binds dimeric IgA on the basolateral membrane, facilitates its internalization by endocytosis, and then cleaves to release the secretory component bound to dimeric IgA.
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