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What are immunoglobulins (Igs)?
Glycoproteins produced by plasma cells that recognize and neutralize foreign objects like bacteria and viruses.
How are antibodies and immunoglobulins related?
They are often used interchangeably, but immunoglobulins are the structural class of antibodies.
What activates B cells to produce antibodies?
Binding to specific antigens, sometimes with T helper cell interaction.
What is the primary function of antibodies?
To bind antigens and eliminate them by neutralization, opsonization, or complement activation.
What are the components of an antibody?
Two identical heavy (H) chains and two identical light (L) chains held by disulfide bonds.
What is the Fc region of an antibody?
The stem of the "Y" that binds to cell receptors and complement proteins, mediating immune responses.
Define the variable (V) and constant (C) regions in antibodies.
The V region binds antigens; the C region defines the immunoglobulin class and mediates effector functions.
What types of light chains exist in antibodies?
Kappa (κ) and Lambda (λ), but only one type is present in each antibody.
What is the hinge region in antibodies?
A flexible region where the antibody arms form a Y shape, allowing movement.
Differentiate between affinity and avidity.
Affinity is the strength of binding between an antibody and antigen; avidity is the total strength of multiple bindings.
What are epitopes?
Specific parts of antigens that antibodies bind to.
What bonds stabilize antibody structure?
Inter-chain and intra-chain disulfide bonds.
What are the five immunoglobulin classes?
IgA, IgD, IgE, IgG, and IgM.
Which antibody is most abundant in blood?
IgG.
Which antibody is the first produced in an immune response?
IgM.
Which antibody is found in secretions like saliva and tears?
IgA.
Which antibody mediates allergic reactions?
IgE.
What is the function of IgD?
It serves as a receptor on immature B cells.
How does IgG protect newborns?
It crosses the placenta to provide passive immunity to the fetus.
What is the structure of IgA in secretions?
A dimer with a J chain and a secretory component.
How does IgM function in the immune response?
As a pentamer, it has high avidity and is highly effective in complement activation.
What role does IgE play in hypersensitivity reactions?
It binds to mast cells and basophils, triggering histamine release in allergic responses.
Which IgG subclass is the most effective at complement activation?
IgG3, followed by IgG1 and IgG2.
Which immunoglobulin is mainly involved in mucosal immunity?
IgA.
What is selective IgA deficiency?
A condition where IgA is absent or decreased, leading to increased susceptibility to infections.
Why is IgM called a "natural antibody"?
It arises early in life and reacts to naturally occurring antigens.
Which antibodies are involved in blood transfusion reactions?
IgM, due to its role in agglutination of red blood cells.
How do antibodies facilitate opsonization?
By coating pathogens to enhance phagocytosis.
Which antibody cannot activate the complement system?
IgG4.
What is the J chain in antibodies?
A polypeptide that joins monomers in IgA and IgM to form dimers or pentamers.
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