[Q] memory B cell
Richard R. Hardy
rr_hardy at fccc.edu
Sun Sep 22 13:39:29 EST 1996
In article <ochi-2009962217260001 at 188.8.131.52>, ochi at super.win.or.jp
(Yoshihiro Ochi) wrote:
>I have questions about memory B cell.
>1. How does B cell become memory B cell ?
>2. How does memory B cell memorise ?
>3. How condition can memory B cell be reactivated and secrete antibody ?
These are certainly interesting questions and by no means completely
solved, even though memory B cells have been recognized as a distinctive
subset since the 70s. I think a memory B cells is generated by T-dependent
activation of a "naive" B cell, typically (always?) in a germinal center.
The naive B cell turns on somatic mutation, looses IgD (thereby expressing
1/10 the previous surface Ig density) and becomes very sensitive to
ligation of it receptor (upregulates fas, downregulates bcl-2), so that
cells with efficient binding (due to mutation) are selected for survival.
Most of these progeny cells also switch to downstream isotypes (IgG). It's
somewhat controversial whether memory cells "memorize" (by this I mean
survive indefinitely) due to altered cell physiology or due to repeated
antigen re-stimulation. The neat thing about memory cells is that they
have high affinity for Ag and therefore can serve as very efficient antigen
presenting cells to T cells. Antigen pulsed memory B cells plus
"secondary" CD4+ T cells form a very good "conjugate" inducing the T cell
to secrete cytokines that then induce the activated memory B cell to
proliferate and generate plasma cells, secreting large amounts of specific
Richard R. Hardy Member, Inst. for Cancer Research
Fox Chase Cancer Center Tel: (215) 728-2463
7701 Burholme Ave. FAX: (215) 728-2412
Philadelphia, PA 19111 E-MAIL: RR_HARDY at fccc.edu
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