Exam 2: Dr. Pharr Antibody Structure and B-cell Development Flashcards
What is an immunoglobulin composed of?
2 identical heavy chains 2 identical light chains Variable region Hinge region Constant region
What is the light chain composed of?
A single variable domain and a single constant domain
What is the heavy chain composed of?
A single variable domain and three to four constant domains
What does the variable region do?
Antigen recognition
What is the hinge region?
Flexible polypeptide structure
What does the constant (Fc) region do?
Determines the effector function of the antibody
What is the constant region recognized by?
Leukocytes and plasma proteins
What are the 5 classes of antibodies defined by?
Heavy chain constant region
What are the 5 classes of antibodies?
IgG IgA IgM IgD IgE
In a primary immune response, wha is the first antibody produced?
IgM
What is it called when later in the immune response additional isotypes are produced?
Isotype switching
Why is it important that the B cell receptor recognizes the native form of an antigen?
The antibody will link the pathogen to the leukocytes and plasma proteins that will eliminate it
What is an epitope?
The part of the antigen bound by the antibody
What can an epitope consist of?
A cluster of amino acids or a portion of a polysaccharide
What can a pathogen express on the surface?
A number of complex proteins and carbohydrates
What must the shape of the antigen binding site be complementary to?
The shape of the the epitope
What is cross-reactivity?
The binding of an antibody to an antigen not used to generate that antibody
What are the reasons for cross-reactivity?
Shared epitope (different antigens share the same epitope) Similar epitope (pathogens express protein or carbohydrate epitopes that resemble host epitopes)
What are polyclonal antibodies?
A mixture of antibodies, each specific for a different epitope from the same antigen
What is a monoclonal antibody?
Antibody originating from a single B cell
The antibody is specific for one epitope
What does the mechanism of immunoglobulin development ensure?
That each lymphocyte expresses an immunoglobulin of a single antigen specificity
What is somatic recombination?
DNA recombination that occurs between gene segments in the immunoglobulin genes
How does the process of somatic recombination contribute to the diversity of antigen-binding sites?
There are multiple copies of gene segments in the light chain gene and the heavy chain gene
What is the construction of the antigen binding site by somatic recombination like?
- Gene segments are used construct the variable region of the light chain gene and the heavy chain gene
- The gene segments differ from one another in short regions called hypervariable regions
- Somatic recombination results in the random additional nucleotides at the joints between gene segments
What is the bone marrow responsible for?
Development of B cells
What is the development of B cells like?
Diverse repertoire of naive B cells produced in the bone marrow–somatic recombination
What is central tolerance?
Removal of immature B cells with specificity for self-proteins
What type of B cells will be transported into the blood from bone marrow?
B cells tolerant to self proteins
What happens during surveillance with naive B cells?
Naive B cells are exported to the periphery to circulate through secondary lymphoid tissues
What happens during the primary immune response to an infection?
- Recognition of antigen
- Activation by helper T cells
- Differentiation to short-lived plasma cells
In a primary immune response, IgM is secreted as a pentamer. Why?
IgM generally possesses low affinity for the antigen epitope. However, the pentameric structure increases the valence from 2 antigen binding site to 10 antigen binding sites
