B Cells Flashcards
Development of B cells occur in which structures
During gestation —> embryo— fetal liver,spleen and BM
After birth—> only in BM
How B cells exits BM
Immature ones at Endosteal niche
As they mature migration toward the vascular niche
Fully differentiated cells exit BM via BV
Phases of B cell development
1- Maturation phase — Foreign Ag Independent = Stem cell to mature-naive B cell
2-Differentiation phase— Foreign Ag dependent = Activated B- ab secreting Plasma or Memory B
Steps of maturation phase of B cell development
Stem cell—> Pro-B—> Pre-B—>Immature B—>Mature B
Which B cell type express enzyme RAG1/2 and TdT
Pro-B cell
DJ rearrangement starts in which phase
Latest stage of pro-B cell
Role of Surrogate Light chain in Pre-B cells
SLC binds to Cytosolic IgH and transfer IgH to membrane
Allelic Exclusion
Expression of a gene on one chromosome prevents expression of the allele on the second chromosome
Causes homogenous B cell receptors
Check points of B cells in BM
First check point caused by no pre-B cell receptor which results with apoptosis — Selects for functional heavy chains
Second checkpoint caused by no B-cell receptor which resulted with apoptosis — Selects functional light chains
Who makes the functional IgM
Immature B cell
If Immature B cells are auto reactive :
Undergo apoptosis — Negative selection, Clonal deletion
Receptor editing — avoiding negative selection
After positive selection B cell expresses
IgM
IgD
What happens when negative selection occurs
Immature B cell is retained in BM
Transition of Type 1 to Type 2 immature B cells derived by
BAFF
B Lymphocyte Activating Factor
What happens in the Early ProB part of the Maturation phase
DJ H chain recombination
Start of VDJ H chain recombination
