Km. Aagaardtillery et Df. Jelinek, INHIBITION OF HUMAN B-LYMPHOCYTE CELL-CYCLE PROGRESSION AND DIFFERENTIATION BY RAPAMYCIN, Cellular immunology, 156(2), 1994, pp. 493-507
In this study, we have analyzed the effects of the immunosuppressive a
gent rapamycin on the activation of highly purified normal human B lym
phocytes. When the polyclonal activators Staphylococcus aureus (SA) an
d soluble CD40 ligand (CD40L) were used to stimulate B cells, rapamyci
n inhibited both interleukin 2 (IL2)-dependent and -independent prolif
eration, as well as IL2-dependent differentiation into antibody-secret
ing cells. Cell cycle analysis indicated that rapamycin inhibited the
progression of SA+IL2-stimulated B cells past the mid-G(1) phase of th
e cell cycle. To begin to identify rapamycin-sensitive signaling event
s essential for B cell activation, we examined the effects of rapamyci
n on p34(cdc2) and p33(cdk2) kinase activities. SA+IL2 stimulation ind
uced the activation of both cyclin-dependent kinases. Of interest, rap
amycin abrogated the activation of both p34(cdc2) and p33(cdk2). Our r
esults indicate therefore that rapamycin inhibits a number of SA- and
CD40L-inducible events that may be necessary for both entry into S pha
se and for permitting subsequent B cell differentiation. These studies
emphasize the utility of this drug as a tool to begin to dissect the
activation pathways utilized by human B eels, as well as to provide im
plications for the therapeutic use of rapamycin in vivo. (C) 1994 Acad
emic Press, Inc.