e n i c i d e M l a t n e m i r e p x E f o l a n r u o J e h T CORRESPONDENCE Randolph J. Noelle: Randolph.Noelle@ Dartmouth.edu OR Micah J. Benson: Benson@IDI.Harvard.edu Abbreviations used: ASC, anti- body-secreting cell; BCR, B cell receptor; BMEM, memory B cell; GC, germinal center; IF, immunofluorescence; KLH, keyhole limpet hemocyanin; MZ, marginal zone; NF, naive follicular; NP, 4-hydroxy-3- nitrophenylacetyl; PB, plasm-a blast; PC, plasma cell; PE, phycoerythrin; SHM, somati- cally hypermutated; sPE, soluble PE; TLR, Toll-like receptor; VACVWR, vaccinia virus West- ern reserve strain. A RT I C L E Distinction of the memory B cell response to cognate antigen versus bystander inflammatory signals Micah J. Benson, Raul Elgueta, William Schpero, Michael Molloy, Weijun Zhang, Edward Usherwood, and Randolph J. Noelle Department of Microbiology and Immunology, Dartmouth Medical School and the Norris Cotton Cancer Center, Lebanon, NH 03756 The hypothesis that bystander inflammatory signals promote memory B cell (BMEM) self- renewal and differentiation in an antigen-independent manner is critically evaluated herein. To comprehensively address this hypothesis, a detailed analysis is presented examin- ing the response profiles of B-2 lineage B220+IgG+ BMEM toward cognate protein antigen in comparison to bystander inflammatory signals. After in vivo antigen encounter, quiescent BMEM clonally expand. Surprisingly, proliferating BMEM do not acquire germinal center (GC) B cell markers before generating daughter BMEM and differentiating into plasma cells or form structurally identifiable GCs. In striking contrast to cognate antigen, inflammatory stimuli, including Toll-like receptor agonists or bystander T cell activation, fail to induce even low levels of BMEM proliferation or differentiation in vivo. Under the extreme condi- tions of adjuvanted protein vaccination or acute viral infection, no detectable bystander proliferation or differentiation of BMEM occurred. The absence of a BMEM response to non- specific inflammatory signals clearly shows that BMEM proliferation and differentiation is a process tightly controlled by the availability of cognate antigen. Life-long immunity is central to the survival of reaction, they colonize the splenic marginal the host. This immunity is engendered by the zones (MZs) and the B cell follicles, where they persistence of memory T cells, memory B cells reside in a quiescent state for months or, likely, (BMEM), and long-lived BM plasma cells (PCs; years (Liu et al., 1988, 1991; Schittek and Amanna et al., 2007; Dörner and Radbruch, Rajewsky, 1990; Anderson et al., 2007). Upon 2007). Long-lasting B cell–mediated immunity rechallenge with cognate antigen, histological has been referred to as serological memory studies in rats observed that BMEM egress to- (Traggiai et al., 2003) and can be sustained by ward the T cell–rich periarteriolar lymphocytic recurrent antigen exposure. In the absence of sheath and, upon receiving T cell help, prol-if periodic exposure to antigen, it is thought that erate and differentiate into plasmablasts (PBs) the production of inflammatory signals to un- situated in both the periarteriolar lymphocytic related antigens serve as mediators sustaining se- sheath and in the splenic red pulp (Liu et al., rologic memory through activation of BMEM in 1991). Kinetic studies indicate that the genera- a noncognate manner. The in vitro and in vivo tion of this response is rapid and peaks 4-5 d response profiles of antigen-specific BMEM to after secondary antigen encounter (Liu et al., cognate antigen and “nonspecific” or bystander 1991; McHeyzer-Williams et al., 2000; Minges inflammatory mediators are analyzed herein to Wols et al., 2007). The PB response dissipates critically evaluate the mechanisms underlying shortly after its initiation, with a subset of PBs the maintenance of serological memory. further differentiating into long-lived PCs res-i BMEM and long-lived PCs are the products dent in the BM (Liu et al., 1991; Manz et al., of the germinal center (GC) reaction and ex- press somatically hypermutated (SHM) immuno- © 2009 Benson et al. This article is distributed under the terms of an Attribu- globulin receptors of the switched isotypes taifotner–Nthoencpoumbmliceartciioanl–Sdhaatere(sAeliekeh–tNtpo:/M/wirwrowr.jSeimte.sorlgic/emnissec/ftoerr mthse.shfitrmstl)s.ixAmfteorntshixs (MacLennan, 1994; McHeyzer-Williams and months it is available under a Creative Commons License (Attribution–Noncom- mercial–Share Alike 3.0 Unported license, as described at http://creativecommons Ahmed, 1999). After BMEM exit from the GC .org/licenses/by-nc-sa/3.0/). The Rockefeller University Press $30.00 J. Exp. Med. Vol. 206 No. 9 2013-2025 www.jem.org/cgi/doi/10.1084/jem.20090667 2013