CELLULAR IMMUNOLOGY 140,237-247(1992) Cholera Toxin Promotes the Proliferation of Anti-p Antibody-Prestimulated Human B Cells’ EVANGELOSD.ANASTASSIOU, *,* HIDEHIRO YAMADA,* DIMITRIOS T. BOUMPAS,* GEORGE C. TSOKOS,*,~ GEORGE THYPHRONITIS,~ JAMES BALOW,* AND JAMES J. MoND=~,~ *Kidney Disease Section, National Institute qf Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and TDepartment of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799 Received September 30, 1991; accepted October 21, 1991 The predominant effect of cholera toxin (CT) on cell growth has been postulated to be inhibitory as a result of its induction of intracellular CAMP. We have recently reported that CT selectively enhances surface DR expression while it inhibits anti-p antibody-induced B lymphocyte prolif- eration. In the present seriesof experiments we studied the effect of CT on in vitro preactivated highly purified (>95% CD20+) human B cells. Cholera toxin enhanced thymidine incorporation of anti-r antibody-preactivated but not of Staphylococcus aureus Cowan I or PMA + ionomycin- preactivated B cells. Concentrations of 100 pg/ml CT stimulated an enhancement of thymidine incorporation equivalent to that of optimal dosesof BCGF. The growth factor-like effect of CT required the complete molecule, since binding of purified B subunit (B-CT) to GM, ganglioside by itself did not reproduce the holotoxin effect. Moreover, B-CT pretreatment of anti-p antibody- primed cells completely neutralized the holotoxin-enhancing effect. Both PGEz, a physiological agent that stimulates intracellular CAMP elevation, and the CAMP analogue, I-bromo-CAMP, mimicked the growth-promoting effect of CT. However, the EDS,,of CT required to augment proliferation in anti-p antibody-preactivated human B cells was approximately 100 times less than the EDSo for CAMP formation. These results demonstrate a specific growth factor-like pro- moting effect of CT on sIg-preactivated highly purified human B cells that may be mediated at least in part through elevation in intracellular CAMP levels. Increased DR expression and stim- ulation of growth of sIg preactivated B cells may explain some of the adjuvant properties of CT following orally or parenterally administered antigens. o 1992 Academic press, IW. INTRODUCTION Cholera toxin (CT),4 a potent exotoxin produced and secretedby Vibrio cholerue, is a multisubunit molecule composed of two structurally and functionally distinct ’ This work was supported in part by the Uniformed ServicesUniversity of the Health Sciences Protocol R083BQ, National Institutes of Health Grants AI24273 and A127465, and Office of Naval Research and Development Command Grant NO00759 1 WROOO 18. The opinions and assertionscontained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Department of Defense or the Uniformed Services University of the Health Services. 2Present address:Department of Microbiology, School of Medicine, University of Patras, Patras 26110, Greece. 3To whom correspondenceshould be addressed at Department of Medicine, A3060, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 208 14-4799. 4 Abbreviations used:CT, cholera toxin; B-CT, B subunit of CT; 8BrcAMP, 8-bromo-cyclic AMP, PDBU, phorbol 12,13-dibutyrate; PGE2, prostaglandin E2. 237 OOO8-8749192 $3.00 Copyright 0 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.