B Cell Development Flashcards
Process of negative selection in the BM
Immature B cell bound to self cell-surface antigen is removed from the repertoire
B cell origin
- hematopoeitic stem cell
- multipotent progenitor
- early lymphocyte progenitor (ELP)
- common lymphocyte progenitor (CLP)
- Pre-B cell
- B cell
When is IgM first expressed on cell surface?
after Light chain rearrangement
Importance of stromal niche cells
Define the fate of developing cell
Role of CXCL12
Controls pre-pro B cell anchoring in correct stromal niche
Role of Il-7/ Il-7 receptor
requried for lineage progression
Role of Cell adhesion molecules
Assist cell anchoring
Role of cKIT/SCF (stem cell factor)
interaction induces intracellular signalling pathways to drive B cell development
Molecular markers that drive VDJ re-arrangement
E2A and EBF
What is an allotype
polymorphisms of the constant regions of the heavy and light chains
What is allelic exclusion?
if the first IgH rearrangement is productive, the second allele will not rearrange and is excluded
What is the result of allelic exclusion?
only 1 rearranged heavy chain per B cell
How self-reactive B cells are eliminated
- multivalent self molecule (apoptosis)
- soluble self molecule (anergic B cell)
- Low-affinity noncross-linking self molecule (mature B cell that isclonally ignorant)
What is receptor editing
If IgM binds self-antigen, B-cell development is arrested and L-chain rearrangement continues and IgM expression is decreased. A new receptor specificity is expressed
Molecules expressed by mature B cells
- MHC II
- CD 40(costim for APC activation)
- CD 21 (act. of B cells by complement)
- CD 19 (corecep with CD21+81)
- CD 81 (corecep with CD19+21)
Role of secondary lymphoid tissue
To increase the chance of encounterding antigen and initiating an immune response
What regulates the migration of B cells to the T zone and follicles?
chemokines
What is somatic hypermutation
- random mutagenesis (single base changes)
- occurs in mature, antigen-activated B-cells
What is affinity maturation?
- an increase in the affinity for the specific antigen of the antibodies produced during a humoral immune response
- prominent in memory immunizations
Types of mature B cells
- plasma cells
- memory B cells
- B-1 cells (express IgM)
- B-2 cells (conventional mature B cells)
- marginal zone B cells
- follicular B cells
