B cell Development and Immunity Flashcards
should you add lymph node pathways
Describe phase 1 of development
Repertoire formation: generation of diverse and clonally selected B cell receptors
Where does it take place?
in bone marrow
Describe Phase 2
negative selection: alteration, inactivation. or elimination of self reactive B cell receptors
Describe phase 3 of development
positive selection: small fraction of B cells selected to become mature B cells in secondary lymphoid tissues
Phase 4 of development
Searching for infection: Recirculation of mature B cells between lymph, blood, and secondary lymphoid tissues
Phase 5 of development
Finding infection: Activation and clonal expansion of B cells by pathogen-derived antigens in secondary lymphoid tissues
Phase 6 of development
Attacking infection: Differentation to antibody secreting plasma cells and memory B cells in secondary lymphoid tissue
How many cells per day begin the process becoming a B cell?
2.5 billion
How many cells/day die because they fail to productively rearrange Ig or are self reactive?
55 billion
how many exit the bone marrow, as mature naive B cells per day?
30 billion
What is a naive B cell?
has not yet encountered cognate antigen
How long can naive B cells circulate?
2-3 days
what happens if naive B cells don’t find antigen?
they die
where do they encounter antigen? what happens when they do?
spleen or lympg nodes; undergo further differentiation if they see their match
What is a critical step in B cell survival?
Producing heavy chain, using surrogate light chain to test it’s integrity
What does the combination of a rearranged light chain and surrogate heavy chain indicate?
end of heavy chain rearrangement, cell survival and cell proliferation
When does light chain rearrangement begin?
after the rearranged heavy chain binds to the light surrogate light chain
Describe heavy chain rearrangement
DJ occurs on both chromosomes, V-DJ attempted first on chromosome 1, then on chromosome 2, then apoptosis if unsuccessful
Describe light chain rearrangement
VJ rearrangement attempted first on kappa gene on chromosomes 1 and 2, then lambda gene on chromosomes 1 and 2, then apoptosis if unsuccessful
Describe the difference between autoreactive and non-autoreactive T cells.
immune cells that are self-reactive are retained in the bone marrow, whereas those that are not mature to express IgD and IgM
what enzyme is responsible for class switching? What else is it responsible for?
AID (activation-induced cytidine deaminase
somatic hypermutation
When can somatic hypermutation take place?
during class switching
What happens when germinal center centrocytes bind with low afinity to surface immunoglobin?
B cell receptor is not cross-linked and the centrocyte cannot present antigen to T cell
what happens when germinal center centrocytes bind with high affinity to surface Ig?
B-cell receptor is cross-linked and antigen is presented to helper T cell.
What does IL-4 induce? What does it inhibit?
IgG1, IgE;
IgM, IgG2a, IgG3
What does IL-5 do?
augments IgA production
What does IFN-gamma induce? Inhibit?
IgG3, IgG2a
IgM, IgG1, IgE
What does TGF-Beta induce? Inhibit?
IgG2b, IgA
IgM, IgG3
What happens when antigen-selected centrocytes mature under the influence of IL-10 secreting helper T cells?
Centrocytes differentiate into plasma cells; make antibodies that fight and terminate current infection
What hapens when antigen selected centrocytes mature under the influence of IL-4?
Centrocytes differentiate into memory B cells act as an investment that prevents further infections from causing disease
what is the germinal center?
collection of B cells (centrocytes) that proliferate and receive antigen from the follicular dendritic cells and interact with helper T cells
What is special about follicular dendritic cells?
They are actually not dendritic cells at all, they just have dendrites on them
What is an HEV?
High endothelial venule, serves as a point of entry for B cells and T cells into the lymph node
