B cells

Question 1

B cell development

Answer 1

Anatomical site: Bone marrow

Stages: HSC > Early Pro-B cell (Heavy chain DJ rearrangement) > Late Pro-B cell (VDJ rearrangement ) > Large Pre-B cell (Pre-BCR with surrogate light chain; RAG re-expression) > Small Pre-B cell (light chain rearrangement) > Immature B cell (Surface IgM expression)

B cell markers: CD19, B220(CD45R), CD43 (lost upon developing into immature B cell)…

Question 2

B cell subsets

Answer 2

Transitional B cells: Immature B cells that have migrated to the spleen for further maturation; All 3 subsets are CD93+

T1: IgMhi CD23-

T2: IgMhi CD23+

T3: IgMlo CD23+; Represent a population of autoreactive anergic B cells

BCR signalling contributes to the fate determination of T2 cells:
Weak- Marginal Zone B cells
Tonic- Follicular II B cells
Strong- Follicular I B cells

B2 cells:

Follicular B cells:
SLO-homing; BAFF-dependent survival in follicular niche; T cell-depensent responses

Marginal Zone B cells:
IgMhi CD1d+ CR2(CD21)+
Noncirculating; Speen-residing; Innate like defence against blood-bourne pathogens; T cell-independnet response; Differentiation into short-lived plasma cells

B1 cells:

B1a: CD5+; Natural antibody production
B1b: CD5-; Primary source of dynamic T cell-independent antibodies

B-1a progenitors are found principally in fetal liver, neonatal spleen & BM

B-1b and B-2 progenitors are found principally in adult BM

B10 cells:
CD1dhi CD5+ CD19hi
IL-10-secreting B cells with regulatory activities