B-IV B-cell function Flashcards
What is required for signaling into the nucleus of a B-cell?
Invariant chain ( consisting of Ig alpha, and beta)
Signaling is crucial for B-cell development and function.
What is the first step in B-cell development during the antigen-independent phase?
Heavy chain locus rearrangement
This occurs in the pro-B cell stage in the bone marrow.
What do pre-B cells express to check if the receptor works?
Surrogate light chain
The pre-B cell receptor includes a μ chain as an invariant surrogate chain.
What is the most common light chain in BCR?
κ chain
The light chain rearrangement is driven by the pre-BCR signaling.
What happens to a naive B-cell upon antigen stimulation?
Activation
This leads to differentiation into plasma cells.
What occurs during the antigen-dependent phase of B-cell development?
Activation and differentiation
If no antibodies bind, the cell undergoes apoptosis.
What is allelic exclusion in B-cell development?
Only one allele is expressed. The other is inhibited by a functional gene product
A productive locus inhibits the other allele to ensure a single functional receptor.
What are the two types of selection in B-cell development?
Positive and negative selection
These processes ensure B-cell tolerance and prevent autoimmunity.
What is the role of the germinal center in B-cell activation?
Formation of antibody-producing cells and affinity maturation
Activated T and B-cells interact here, leading to higher affinity antibodies.
What cytokines are involved in class switching of B-cells?
IFN-γ, IL-4, IL-5, TGF-β, IL-21
These cytokines help produce different antibody classes beyond IgM.
What is the function of plasma cells?
High Ig secretion, low/no BCR expression
Plasma cells are fully differentiated and do not proliferate in response to antigens.
What is the function of the FcγRIIB receptor on B-cells?
Inhibits BCR signaling
This downregulates immune responses.
What types of antigens require T-cell help for B-cell activation?
Thymus dependent antigens (TD Ag)
These include proteins and lead to memory cell formation.
What is the difference between thymus independent antigens (TI Ag) and thymus dependent antigens?
TI Ag do not require T-cell help and mainly induce IgM production
They do not undergo isotype switching or affinity maturation.
What is the hapten-carrier effect?
B-cell processes carrier protein and presents peptide to T-cell, enabling T-cell to activate the B-cell and recognize a different epitope than the B-cell
This enables the T-cell to activate the B-cell, recognizing different epitopes.
What is the unique marker for the B-1 subset of B-cells?
CD5
B-1 cells primarily produce IgM and are found in mucosal sites.
What are the functions of antibodies?
Neutralization, opsonization, cellular cytotoxicity, mast cell activation, complement activation
Each function is associated with specific antibody classes.
What is the difference between polyclonal and monoclonal antibodies?
Polyclonal: several B-cell clones; Monoclonal: one B-cell clone
Monoclonal antibodies are produced using hybridoma technology.
What happens to naive B-cells when there is no antigen present in the lymph node?
They undergo apoptosis
This process ensures that only activated B-cells persist.
What role does activation-induced deaminase (AID) play in B-cell function?
Causes somatic mutations in CDR regions
This enhances the affinity of antibodies produced.
What do bone-marrow stromal cells do?
Bind to pro-B-cells, secrete IL-7 which causes proliferation and development into pre-B-cells
What is the different between pro-B-cells and pre-B-cells?
pre-B-cells expresses pre-B receptor at surface; H-chain genes are rearrenged
What is the function of the pre-BCR
To test if the heavy chain is functional, and signal to the light chain locus to begin rearrangement if so
Which is the more common light chain?
Kappa
