© The Rockefeller University Press, 0022-1007/2000/3/883/ $5.00
The Journal of Experimental Medicine, Volume 191, Number 5, March 6, 2000 883-890
CD5 Maintains Tolerance in Anergic B Cells
Keli L. Hippena,
Lina E. Tzea, and
Timothy W. Behrensa
a Center for Immunology, Department of Medicine, University of Minnesota Medical School, Minneapolis, Minnesota 55455
Correspondence to:
Keli L. Hippen, [same address]. Tel:612-625-5168 Fax:612-625-2199 E-mail:keli.l.hippen-1{at}tc.umn.edu.
Released online: 6 March 2000
Clonal anergy of autoreactive B cells is a key mechanism regulating tolerance. Here, we show that anergic B cells express significant surface levels of CD5, a molecule normally found on T cells and a subset of B-1 cells. Breeding of the hen egg lysozyme (HEL) transgenic model for B cell anergy onto the CD5 null background resulted in a spontaneous loss of B cell tolerance in vivo. Evidence for this included elevated levels of anti-HEL immunoglobulin M (IgM) antibodies in the serum of CD5-/- mice transgenic for both an HEL-specific B cell receptor (BCR) and soluble lysozyme. "Anergic" B cells lacking CD5 also showed enhanced proliferative responses in vitro and elevated intracellular Ca2+ levels at rest and after IgM cross-linking. These data support the hypothesis that CD5 negatively regulates Ig receptor signaling in anergic B cells and functions to inhibit autoimmune B cell responses.
Key Words:
CD5, hen egg lysozyme, B cell, anergy, signal transduction