2&3 Flashcards
What are Immunoglobulins?
Immunoglobulins are globulin proteins that make up about 20% of the protein in blood plasma. They are found in serum, tissue fluids, and on the surface of B cells, produced by plasma cells in response to an antigen, and function as antibodies.
What is the structure of an Immunoglobulin?
An Immunoglobulin is a Y-shaped molecule composed of two heavy chains and two light chains, with a hinge region, antigen-binding sites, a variable region, and a constant region.
What are the components of the light chain in Immunoglobulins?
The light chain has one variable (V) region at the amino terminal end and one constant (C) region at the carboxy terminal end. It can be either kappa (κ) or lambda (λ).
What determines the classes of Immunoglobulins?
The amino acid composition and sequence of the heavy chains determine the five classes of Immunoglobulins: IgG, IgM, IgA, IgD, and IgE.
What is the hinge region in Immunoglobulins?
The hinge region is a flexible area rich in cysteine residues that allows for movement. It is found in IgG, IgA, and IgD, while IgM and IgE lack a hinge region.
What is the significance of hypervariable regions in Immunoglobulins?
Hypervariable regions in the variable region of both light and heavy chains form the antigen-binding site (paratope) and are crucial for the specificity of antibody-antigen interactions.
What is the difference between affinity and avidity in Immunoglobulins?
Affinity refers to the strength of binding between a single binding site of an antibody and an antigen, while avidity refers to the overall strength of interaction between an antibody and an antigen.
What are the functions of antibodies?
Antibodies recognize and bind antigen complexes (Ag-Ab) and promote the removal of these complexes through the activation of effector mechanisms.
What are isotypes, allotypes, and idiotypes?
Isotypes are defined by antigenic differences in the constant region of heavy chains. Allotypes are additional antigenic features that vary among individuals. Idiotypes are the antigenic determinants formed by specific amino acids in the hypervariable region.
What is the structure of IgG?
IgG is a monomer with a molecular weight of 150,000, a serum half-life of 28 days, and is the most abundant antibody in internal body fluids.
What is the role of IgA?
IgA exists as a monomer in serum and as a dimer in external secretions, playing a key role in mucosal immunity by preventing attachment of bacteria and viruses to mucosal membranes.
What is unique about IgM?
IgM is a pentamer in serum, accounts for about 10% of the serum antibody pool, and is the most efficient immunoglobulin in agglutination and complement activation.
What is the function of IgE?
IgE mediates immediate hypersensitivity reactions and participates in host defenses against certain parasites by binding to mast cells and eosinophils.
What is class switching in B cells?
Class switching is the process by which a B cell changes the class of immunoglobulin produced while preserving antigenic specificity, involving somatic recombination.
What is the significance of interleukins in class switching?
The control of class switching is dependent on concentrations of interleukins, such as IL-4 for IgE and IL-5 for IgA, as well as the interaction of CD40 on B cells with CD40 ligand on helper T cells.
What is the overall structure of a typical Immunoglobulin?
A typical Immunoglobulin is composed of two identical heavy chains and two identical light chains, with variable domains forming the antigen-combining site.
What does affinity define?
Affinity defines the strength of interaction between a single Ag-combining site and an epitope.
What does avidity refer to?
Avidity refers to the cumulative interactions of several combining sites with an Ag.
How are Ig isotypes defined?
Ig isotypes (classes) are defined by the differences in their H chain C region.
What role does Ig play in the immune system?
Ig plays a major role in defense mechanism and protection against infections.
Which antibody is considered the most protective?
IgG is considered the most protective antibody.
What is the predominant antibody isotype in secretions?
IgA is the predominant antibody isotype present in secretions.
Which antibody predominates in the primary immune response?
IgM predominates in the primary immune response.
What is the function of IgD?
IgD is an Ag specific receptor on mature B cells.
