LB 0910

B lymphocytes
Subsets, Control of antibody
production and autoreactivity

Peripheral B cells
•Central selection during bone marrow
maturation
•Survival B cells incorporate in the
peripheral pool as small recirculating B
cells
•A fraction is selected in anatomically
distinct sites as sessile large cells with
partially activated phenotype -> MZB and
B1 cells

B lymphocyte subsets
•B1 lymphocytes
–CD5+
–Peritoneal cavity and MZB
–Autoreactive, low affinity
–IL-10 production upon TLR engagement
–Function: natural Ab ? First line of defense ?
•B2 lymphocytes
–Conventional peripheral B lymphocytes
–Develop in follicles

Peripheral B cell maturation
•Transitional B cells: HSA++, sIgM+, CD23-
(FcεRII), CD21/35low (C’R)
•Positive selection towards B2 cells (not clear?):
requirement for Igαchain
•Follicular B cells sIgM+, CD23+
•Tonic signaling by BCR required for survival

B1 lymphocytes
•Preferentially generated from fetal HSC as CD5+ B cells
•Partially autoreactive repertoire
•Important in the production of natural antibodies (IgM)
•Present in pleural and peritoneal cavities (Ab generation
for mucosal surfaces), IgA-producing cells
•Early responses to local infections