Exam II - B Cell Questions Flashcards
Where do B cells mature?
Bursa of Fabricious (birds) or Bone Marrow
Which 2 Igs make up the BCRs?
IgM, IgD
What is the function of a BCR?
To recognize and react to an antigen
What is the life span of most B Cells?
Most are short lived. Memory B cells are long-lived
What are the 2 ‘hallmark events’ of B cell development?
- expression of antigen receptor genes by the immature B cell
- functional competence
Which cytokine stimulates B Cell proliferation?
IL-7
Which BCR component is expressed on Pre-B cells?
IgM heavy chains
Which BCR component is expressed on mature naive B cells?
IgD along with IgM
At which step of maturation is functional competence achieved?
Full maturation; when B cell expresses both IgM and IgD
Where are B cells found after maturation?
Peripheral lymphoid organs and tissues (lymph nodes, MALT, GALT, etc…)
What is the fate of Ag bound to the BCR?
the antigen is endocytosed into a phagosome, merges with a lysosome to become a phagolysosome, which digests the antigen so that it can be presented by MHC class II molecules
What is the signal transduction protein associated with the BCR?
CD79
Which gene regions encode the lambda and kappa light chain proteins?
Chromosome 2 for kappa chain; Chromosome 22 for lambda chain
What is the purpose of somatic gene rearrangement?
It results in Ig diversity, and ensures that only B cells will produce immunoglobulins
Which light chain is rearranged 1st?
kappa
Which enzymes are responsible for cleaving DNA at recombination requences?
Recombinases
What cell types synthesize recombinase?
T and B lymphocytes
Which enzymes are responsible for repairing the double strand breaks?
DNA repair enzymes
DNA-dependent protein kinase is an example of a:
DNA repair enzyme
Which species/breed is known to suffer from Severe Combined Immunodeficiency (SCID)?
Arabian foals
Which lymphocytes will an animal with SCID be unable to synthesize?
T and B lymphocytes
Which receptors constitute the B cell coreceptor complex?
CR2, CD19, CD81
The CD21 receptor binds to:
C3d
The binding of which receptor and ligand facilitates activation of a B cell?
CD40 to CD40L
What can a TH cell secrete to help activate a B cell?
IL-2, IL-4, IL-6
What cell type do most B cells differentiate into?
Plasma cells
“terminally differentiated B cells” are also called:
plasma cells
Where are plasma cells found?
extrafollicular sites in peripheral lymphoid organs, and at a few inflammatory sites. Few are found in circulation
What is a tumor of plasma cells called?
multiple myeloma.
How do plasma cell tumors arise?
They are the result of a random mutation in a single B cell
What kind of Ig does a plasma cell tumor produce?
They produce homogenous Ig called Myeloma Protein (M Protein)
What is light chain disease?
Myeloma in which Ig light chains are produced alone or are predominant
What are the consequences of light chain disease?
They pass through the glomerulus and are excreted in the urine. They are toxic to renal tubular cells and cause renal failure
These are proteins that precipitate when heated to 60oC
Bence Jones proteins
What is the life span of Bence Jones proteins?
These cells survive indefinitely in cell culture
Which proteins regulate somatic mutations?
Protein antigens
What is the net result of affinity maturation?
A population of B cells that produce antibodies with significantly higher affinities for antigen
What is required for the development of memory B cells?
T cell-derived cytokines
Which cells to T-independent antigens bind?
B cells
What is the 1o antibody produced in response to T-independent Ags?
IgM
What happens to lymphocutes bearing receptors specific for self-peptides?
They are deleted at an early stage of development
Define mitogen
A mitogen is capable of inducing cell division in a high percentage of T or B cells
List some examples of T and B cell mitogens
Pokeweed, LPS, Protein A, Phytohemagglutinin, Concanavalin A.
How are the properties of mitogens used clinically?
To assess the ability of lymphocytes from patients with suspected immunodeficiency
Which Ig shows N-region diversity?
IgH
TdT is expressed by Pro-B cell only during the stage of IgH gene rearrangement. Therefore, only IgH shows N-region diversity.
During which stages are the RAGs expressed?
Pro, Pre
During which stage(s) is TdT expressed?
Just Pro-B
What are the progeny of B cells?
plasma cells and memory cells
What is the surrogate light chain made up of?
It is made up of two invariant proteins called VpreB and λ5
More than 40% of the total proteins produced by a plasma cell are:
antibodies
Ensures that one B cell will react with only one antigenic determinant and will produce antibodies to only that antigen:
allelic exclusion
What are the signal transduction molecules on Pro-B cells?
Ig-alpha and Ig-beta
What is the most important cytokine for T and B cell development?
IL-7
If we see IgD expressed on a B cell, at what developmental stage is that B cell?
Mature B cell
At which stage of B cell development do we no longer see TdT?
Precursor B cell
Made up of 2 invariant proteins called VpreB and lambda-5:
surrogate light chain
This is a process that attempts to rescue a self-reactive B cell from undergoing apoptosis:
Receptor editing
Full maturation of a B cell is signaled by the coexpression of ____ and ____ on the cell surface.
Full maturation of a B cell is signaled by the coexpression of IgM and IgD on the cell surface.
Where to Helper T cell-B cell interactions occur?
at the junction of the cortex and paracortex
