CpG ODN-induced NF-kB activation / IL-6 secretion through CD21-TLR9 dependent B cell signaling? (128.34)

Abstract

Abstract Human CR2, a receptor for complement C3d, EBV-gp350, CD23 and IFN-ƒÑ is a B lymphocyte membrane glycoprotein that plays a central role in immunity and autoimmunity. Dysfunction or absence of CR2 promotes development of anti-DNA antibodies in models of systemic lupus erythematosus. In this study, we show that CpG ODN and TLR9 bind to CR2 using ELISA and surface plasmon resonance (SPR). Using SPR, in which carboxy-terminal biotin-tagged CR2 SCR1-4 on a streptavidin chip and CpG ODN and TLR9 as solution phase analyte were studied, the calculated equilibrium dissociation constant (kd/ka) for this binding, reveal 3.1¡Ñ10-2/5.4¡Ñ10-5 s-1 and /1.1¡Ñ10-2/2.4¡Ñ106 s-1 M-1 with a maximal KD of 571 nM and 42 nM respectively. Monoclonal antibodies developed against the first 2 short consensus repeats (SCR) blocked full-length CR2 binding to CpG ODN and TLR9 by ELISA, identically to their effect on C3d binding, indicating the first two SCR involved in this binding. Further more, treatment with chloroquine, a known inhibitor of TLR9 signaling blocks the CR2-TLR9 interaction by ELISA. We are currently determining whether, by using activation of Namalwa B cells with CpG ODN, blockade of CR2 inhibits the CpG-induced NF-kB activation and induction of IL-6 release. These data suggest that CR2 may functionally interact with TLR9 on B cells.