Producing Regulatory B Cells − IL-10 Cell-Activating Factor in The

Home , Interleukin 10, Regulatory B cell

Cutting Edge: Novel Function of B Cell-Activating Factor in the Induction of IL-10−Producing Regulatory B Cells

This information is current as Min Yang, Lingyun Sun, Shengjun Wang, King-Hung Ko, of September 24, 2021. Huaxi Xu, Bo-Jian Zheng, Xuetao Cao and Liwei Lu J Immunol 2010; 184:3321-3325; Prepublished online 5 March 2010; doi: 10.4049/jimmunol.0902551

http://www.jimmunol.org/content/184/7/3321 Downloaded from

Supplementary http://www.jimmunol.org/content/suppl/2010/03/05/jimmunol.090255 Material 1.DC1 http://www.jimmunol.org/ References This article cites 22 articles, 11 of which you can access for free at: http://www.jimmunol.org/content/184/7/3321.full#ref-list-1

Why The JI? Submit online.

• Rapid Reviews! 30 days* from submission to initial decision by guest on September 24, 2021 • No Triage! Every submission reviewed by practicing scientists

• Fast Publication! 4 weeks from acceptance to publication

*average

Subscription Information about subscribing to The Journal of Immunology is online at: http://jimmunol.org/subscription Permissions Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts

The Journal of Immunology is published twice each month by The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2010 by The American Association of Immunologists, Inc. All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. Cutting Edge: Novel Function of B Cell-Activating Factor in the Induction of IL-10–Producing Regulatory B Cells † ‡ ‡ Min Yang,* Lingyunx Sun, Shengjun Wang, King-Hung Ko,* Huaxi Xu, Bo-Jian Zheng,* Xuetao Cao, and Liwei Lu* Although B cells have been shown to possess a regulatory lating data indicate that IL-10–producing B cells possess function, microenvironmental factors or cytokines in- a regulatory function in the development of autoimmune volved in the induction of regulatory B cells remain diseases, microenvironmental factors and/or cytokines in- largely uncharacterized. B cell-activating factor (BAFF), volved in inducing regulatory B cell differentiation remain a member of TNF family cytokines, is a key regulator for largely uncharacterized (9, 10). B cell maturation and function. In this study, we detected B cell-activating factor (BAFF), a member of TNF family signiﬁcantly increased numbers of IL-10–producing cytokines, is a key regulator for B cell maturation and survival. Downloaded from B cells in BAFF-treated B cell cultures, an effect specif- Analyses of BAFF-deﬁcient mice reveal a fundamental role of ically abrogated by neutralization of BAFF with TACI- BAFF during the transition from immature T1 to T2 B cells Fc. BAFF-induced IL-10–producing B cells showed a (11). In addition to its crucial role in the maintenance of distinct CD1dhiCD5+ phenotype, which were mainly peripheral B cell pool, BAFF has been found to be essential for MZ B cell development (12). New evidence from BAFF-

derived from marginal zone B cells. Moreover, BAFF + + http://www.jimmunol.org/ transgenic mice indicates that BAFF induces CD4 Foxp3 activated transcription factor AP-1 for binding to IL- T cells to suppress T cell response through an indirect B cell- 10 promoter. Notably, BAFF treatment in vivo increased dependent manner, suggesting a regulatory role of BAFF in- the number of IL-10–producing B cells in marginal zone vivo (13). In this study, we report a novel function for BAFF regions. Furthermore, BAFF-induced IL-10–producing in inducing the differentiation of IL-10–producing B cells B cells possess a regulatory function both in vitro and with a CD1dhiCD5+ phenotype. Moreover, we show that in vivo. Taken together, our ﬁndings identify a novel BAFF-induced IL-10–producing B cells are mainly differen- function of BAFF in the induction of IL-10–producing tiated from the MZ B cell subset with a regulatory function in

regulatory B cells. The Journal of Immunology, 2010, suppressing T cell proliferation and Th1 cytokine production. by guest on September 24, 2021 184: 3321–3325. Furthermore, in vivo transfer of BAFF-induced CD1dhiCD5+ B cells significantly inhibited the arthritis development in CIA xtensive studies have demonstrated the prominent mice. Thus, our findings identify a novel role of BAFF in functions of B cells in Ab production and Ag pre- inducing regulatory B cell differentiation. E sentation; however, certain B cell subsets have been Materials and Methods recognized as immune regulators through cytokine production Mice and reagents (1). Early studies revealed a suppressive role of B cells via IL- 2 2 DBA/1J, C57BL/6, NOD, and B6.IL-10 / mice were purchased from 10 production in the pathogenesis of experimental autoim- 2 2 The Jackson Laboratory (Bar Harbor, ME). B6.IL-10 / mice backcrossed mune encephalomyelitis (2, 3). Lines of evidence have shown to the DBA/1J background for 10 generations were used in this study. All the existence of regulatory B cells in murine models of experimental protocols were approved by the Institutional Animal Care collagen-induced arthritis (CIA) (4). Transitional 2 (T2)- and Use Committee. Unless otherwise indicated, all Abs were obtained marginal zone (MZ) precursor B cells have been shown to from BioLegend (San Diego, CA), and reagents were from R&D Systems (Minneapolis, MN). suppress the development of experimental arthritis and lupus in mice (5, 6). Recently, studies by Yanaba et al. (7, 8) have Cell culture and flow cytometric analysis characterized an IL-10–producing regulatory B cell subset Splenic B cells were purified with CD19 or B220 mAb-coated microbeads hi + with a unique CD1d CD5 phenotype. Although accumu- (Miltenyi Biotec, Bergisch Gladbach, Germany), and the purity was .95%.

*Department of Pathology and Center of Infection and Immunology, The University of The online version of this article contains supplemental material. Hong Kong, Hong Kong; †Department of Rheumatology, Afﬁliated Drum Tower ‡ Abbreviations used in this paper: BAFF, B cell-activating factor; BCMA, B cell matu- Hospital, Nanjing University Medical School, Nanjing; Department of Immunology, x ration Ag; BR3, BAFF receptor; ChIP, chromatin immunoprecipitation; CIA, collagen- Jiangsu University, Zhenjiang; and Institute of Immunology and National Key Labo- induced arthritis; DC, dendritic cell; FO, follicular; MZ, marginal zone; NF, newly ratory of Medical Immunology, Second Military Medical University, Shanghai, China formed; PIM, PMA, ionomycin, and monensin; T2, transitional 2; TACI, transmem- Received for publication August 17, 2009. Accepted for publication January 26, 2010. brane activator and calcium-modulator and cyclophilin ligand-interactor.

This work was supported by grants to L.L. from the Research Grants Council of Hong Ó Kong and the National Natural Science Foundation of China and Hong Kong Research Copyright 2010 by The American Association of Immunologists, Inc. 0022-1767/10/$16.00 Grants Council Joint Research Scheme. Address correspondence and reprint requests to Dr. Liwei Lu, Department of Pathology and Center of Infection and Immunology, The University of Hong Kong, Pokfulam Road, Hong Kong, China. E-mail address: [email protected] www.jimmunol.org/cgi/doi/10.4049/jimmunol.0902551 3322 CUTTING EDGE: ROLE OF BAFF IN IL-10–PRODUCING B CELL DIFFERENTIATION

Purified B cells were cultured in the presence or absence of recombinant T cell proliferation assay BAFF (20 ng/ml) for 72 h. For intracellular staining of IL-10, PMA (50 ng/ + 2 3 5 ml; Sigma-Aldrich, St. Louis, MO), ionomycin (500 ng/ml; Sigma-Aldrich), Sorting-purified and CFSE-labeled CD4 CD25 T cells (5 10 cells/well) and monensin (2 mM; BioLegend) were added to the culture for the last 5 h were cultured in a 24-well plate precoated anti-CD3 (2 mg/ml) and anti- CD28 (2 mg/ml). Purified CD19+ B cells or BAFF-induced CD1dhiCD5+ B before flow cytometric analysis (8). In separate experiments, B cell subsets 2/2 were sorted with an Epics Altra flow cytometer (Beckman Coulter, Fullerton, cells from wild-type DBA or IL-10 mice were cocultured with those CA), and the purity was routinely .96%. T cells at a ratio of 1:1 for 72 h before flow cytometric analysis. Administration of BAFF protein in vivo and induction of CIA Immunofluorescence microscopy DBA/1J mice were i.v. injected with 100 mg BAFF protein. Three days later, Cytospin-prepared slides of cultured B cells and frozen sections of spleens were 2 both splenocytes and frozen sections were prepared for flow cytometric fixed in acetone at 20˚C for 10 min, blocked in 1% BSA, stained with analysis and immunofluorescence microscopy, respectively. The CIA was CD19-PE and IL-10-FITC, mounted, and monitored under microscope induced in DBA/1J mice as described previously (15, 16). On the day of (Axiovision; Zeiss, Oberkochen, Germany). second immunization, 5 3 105 BAFF-induced CD1dhiCD5+ B cells from 2 2 wild-type DBA or IL-10 / mice were transferred to mice in the treatment Real-time PCR analysis group by i.v. injection. Eight weeks later, serum titers of CII-specific-IgG were measured by ELISA as reported previously (16). The expression levels of IL-10, BAFF receptor (BR3), B cell maturation Ag (BCMA), transmembrane activator and calcium-modulator and cyclophilin Statistics ligand-interactor (TACI), and AP-1 transcripts were measured by real-time PCR as previously described (14), in which fold differences were calculated Unless otherwise indicated, statistical analysis was performed using the with normalization to GAPDH and controls. unpaired Student t tests. A value of p , 0.05 was considered significantly different. Downloaded from Chromatin immunoprecipitation assay The chromatin immunoprecipitation (ChIP) assay was conducted using the Results ChIP assay kit following the manufacturer’s protocol (Upstate Biotechnology, BAFF induces IL-10–producing B cell differentiation in culture Lake Placid, NY). Briefly, purified MZ-B cells were treated with BAFF for To evaluate the effect of BAFF on B cell differentiation and 15 and 120 min, respectively. Normal rabbit IgG and c-Jun Abs (Cell Sig- + naling Technology, Beverly, MA) were used to immunoprecipitate DNA cytokine production, we cultured splenic CD19 B cells, pre- http://www.jimmunol.org/ fragments. PCR then was conducted by using IL-10 promoter specific pri- treated with or without TACI-Fc (a soluble BAFF blocker), in mers: sense, 59-TTGGGTAACTGA GTGCTAA-39, and antisense, 59-GA- the presence of BAFF for 72 h. ELISPOT analysis showed that ACTGGTC GGAATGAA-39. BAFF treatment significantly increased the frequency of IL-10– producing B cells, an effect specifically abrogated by the neu- ELISPOT/ELISAs tralization of BAFF with TACI-Fc (Fig. 1A). Moreover, the Purified splenic B cells or B cell subsets were cultured in IL-10–coated elevated levels of IL-10 in culture supernatant were confirmed Multiscreen 96-well plates (Millipore, Billerica, MA) for 72 h and detected by by a standard ELISA assay (Fig. 1A, Supplemental Fig. 1A). AP-conjugated goat anti-mouse IgG (H+L). For cytokine detection, ELISA g Upon increasing its concentrations from 2 to 20 ng/ml, BAFF

plates were coated with anti-mouse IL-10 or IFN- , and cytokine levels were by guest on September 24, 2021 + detected with IgG1-HRP as described previously (15). treatment signiﬁcantly increased the frequency of IL-10 B cells

FIGURE 1. BAFF induces IL-10–producing B cell differentiation in vitro. A, Frequencies of IL-10–producing B cells determined by ELISPOT. Splenic CD19+ B cells were incubated in the presence or absence of BAFF (20 ng/ml) for 72 h with B cells pretreated with TACI-Fc (200 ng/ml) as control. Results represent mean values of spot-forming cells per 105 CD19+ B cells from eight independent experiments. ELISA determinations of IL-10 secretion in culture supernatants are also shown (mean 6 SEM); **p , 0.01. B, Splenic CD19+ B cells were cultured with BAFF at various concentrations for 72 h, and the number of IL-10– secreting B cells was determined by ELISPOT. Data represents five separate experiments. C, Flow cytometric analysis of IL-10–producing B cell. B cells from 2 2 wild-type DBA and IL-10 / mice were treated with BAFF for 72 h. PMA, ionomycin, and monensin (PIM) were added for the last 5 h before immunostaining. Percentages indicate mean values (6 SEM; n = 6). D, Cytospin preparations of cultured B cells with or without BAFF treatment were stained with CD19-PE and IL-10-FITC (IgG2a, k-FITC as isotype control). The arrows indicate CD19+IL-10+ B cells (original magnification 3200). E, Phenotypic analysis of IL-10+ 2 (thick line) or IL-10 (thin line) B cells from BAFF-treated B cell cultures for 72 h by flow cytometry. PIM were added to the culture for the last 5 h. Gray- shaded histograms indicate the isotype staining. Results represent three independent experiments. The Journal of Immunology 3323 in a linear fashion, with its maximal effect detected at a concentration of 50 ng/ml. However, a higher concentration of BAFF (200 ng/ml) resulted in markedly reduced frequency of IL-10–producing B cells in culture (Fig. 1B). Flow cytometric analysis revealed that the percentages of IL-10+ B cells were substantially increased from 0.8 6 0.2 to 6.5 6 1.2% during a 3-d culture of BAFF-treated B cells (Fig. 1C), which was further confirmed by immunofluorescent microscopy (Fig. 1D), indicating that BAFF treatment can induce IL-10 production in splenic B cells. Accordingly, BAFF was shown to induce the expansion of IL-10+ B cells in culture (Supplemental Fig. 1B). However, BAFF showed no synergistic effect on IL-10 induction with either LPS or anti-CD40 treatment (Supple- mental Fig. 2). To characterize BAFF-induced IL-10–producing B cells, flow cytometric analysis revealed that IL-10+ B cells displayed a CD21hiCD23lo phenotype similar to MZ B cells. IL-10+

B cells were also positively stained for CD5 with high levels of Downloaded from CD1d expression (Fig. 1E), which expressed moderate levels of CD80, CD86, CD43, CD40, and CD83 but exhibited high densities of MHC class II. Furthermore, CD1dhiCD5+ Bcells were the major subset responsible for the IL-10 secretion (Supplemental Fig. 3). FIGURE 2. BAFF induces IL-10 production in MZ B cells. A, Splenic NF lo lo lo hi hi lo (CD21 CD23 ), FO (CD21 CD23 ), and MZ (CD21 CD23 ) B cells http://www.jimmunol.org/ BAFF-induced IL-10–producing B cells are mainly derived from MZ were sorting-purified and cultured with or without BAFF for 72 h. The fre- B cell subset quencies of IL-10–producing B cells were determined by ELISPOT. Values represent mean numbers of spot-forming cells per 105 B cells from five in- To identify the B cell subset(s) from which IL-10–producing B dependent experiments; **p , 0.01. B, Expression of BAFF receptor transcripts cells were differentiated, sorting-purified newly formed (NF) in FO B cells (N) and MZ B cells (n) evaluated by real-time PCR analysis. Values B cells, MZ B cells, and follicular (FO) B cells were cultured represent mean ratios of BR3, BCMA, and TACI transcripts normalized to with BAFF (20 ng/ml). We found that IL-10–producing B GAPDH transcript levels. Results are representative of three independent ex- cells were mainly derived from the MZ B cell subset, whereas periments; *p , 0.05; **p , 0.01. C, Expression of BAFF receptors on MZ B + cells (thick line) and FO B cells (thin line) determined by flow cytometry. Gray- very few IL-10 B cells generated from FO cell fraction (Fig. by guest on September 24, 2021 + shaded histograms indicate the isotype staining. Results represent three in- 2A). However, no IL-10 B cells were detected from cultured dependent experiments. D, Sorting-purified MZ B cells from normal mice were NF B cells. These data indicate a role of BAFF in preferen- treated with BAFF for various time intervals. Values represent mean ratios of IL- tially inducing MZ B cell differentiation into IL-10–pro- 10 and AP-1 transcripts normalized to GAPDH transcript levels as quantified by ducing B cells. real-time PCR. Results are representative of three independent experiments; To assess whether MZ and FO B cells differentially express *p , 0.05; **p , 0.01. E, ChIP analysis of AP-1 (c-Jun) binding to the IL-10 BAFF receptors, quantitative PCR analysis of RNA samples promoter in BAFF-stimulated MZ B cells. Sorting purified MZ B cells were from freshly purified B cell subsets revealed that MZ B cells treated with BAFF for 15 or 120 min, respectively. Immunoprecipitations were conducted using either c-Jun or normal rabbit IgG-specific Abs. Samples were expressed much higher levels of TACI and BCMA mRNA normalized to input DNA controls. expression with a lower level of BR3 transcripts when compared with FO B cells (Fig. 2B), which were consistent with the immunofluorescent staining profile of BAFF receptors on increase in the frequencies of IL-10–producing B cells (Fig. MZ and FO B cells by flow cytometry (Fig. 2C). Further- 3A). Moreover, immunofluorescent microscopy revealed that more, we prepared mRNA samples from BAFF-treated MZ B CD19+ IL-10–producing B cells were mainly located at MZ cells at various time intervals and screened a panel of tran- regions in BAFF-treated mice (Fig. 3B). Thus, these results scription factors for IL-10 gene by real-time PCR analysis. As indicate that increased levels of BAFF enhance the generation shown in Fig. 2D, AP-1 exhibited a rapid 4-fold increase only of IL-10–producing B cells in vivo. 15 min after BAFF stimulation. Notably, IL-10 transcripts in hi + MZ B cells displayed a 6-fold increase upon BAFF treatment. BAFF-induced CD1d CD5 B cells possess regulatory functions both Further analysis by a ChIP assay demonstrated that BAFF in vitro and in vivo stimulation activated AP-1 (c-Jun) for binding to IL-10 pro- To verify whether BAFF-induced IL-10–producing B cells moter region (Fig.2E). possess a regulatory function, we purified BAFF-induced 2 2 CD1dhiCD5+ B cells from both wild-type DBA and IL-10 / BAFF treatment induces the generation of IL-10–producing B cells mice and incubated them with CD3/CD28-activated T cells in vivo (Fig. 4A). T cell proliferation was significantly suppressed by To determine whether BAFF exerts any effects on IL-10– BAFF-induced CD1dhiCD5+ B cells from wild-type mice but 2 2 producing B cell differentiation in vivo, we i.v. injected BAFF not those from IL-10 / mice. Moreover, treatment of co- protein into normal mice and examined both frequencies and cultures with anti–IL-10 mAb abrogated the inhibitory effects absolute numbers of IL-10–producing B cells in the spleen 3 of B cells on T cell proliferation, suggesting that the sup- d after treatment. Flow cytometric analysis showed an ∼4-fold pressive function of BAFF-induced B cells is mediated by IL- 3324 CUTTING EDGE: ROLE OF BAFF IN IL-10–PRODUCING B CELL DIFFERENTIATION

FIGURE 3. BAFF promotes the differentiation of IL-10+ B cells in vivo. A, 2 2 Frequencies of splenic IL-10+ B cells from wild-type DBA and IL-10 / mice with or without BAFF treatment (100 mg/mouse) as detected by flow cytometry. PIM stimulation was performed for 5 h before IL-10 staining. Downloaded from The absolute numbers of IL-10+ B cells in the spleens were also shown (n =5; *p , 0.05). B, Frozen sections of spleens from BAFF-treated wild-type DBA FIGURE 4. BAFF-induced CD1dhiCD5+ B cells possess a regulatory mice were immunostained with CD19-PE and IL-10-FITC. The arrows in- + 2 + + function both in vitro and in vivo. A, CFSE-labeled CD4 CD25 T cells (T) dicate the CD19 IL-10 B cells located at the MZ regions (original mag- + hi + 3 were cocultured with CD19 B cells (B) (I), CD1d CD5 B cells from nification 100). 2 2 2 2 BAFF-treated IL-10 / B cells (induced B [IL-10 / ]) (II), CD1dhiCD5+ B cells from BAFF-treated wild-type B cells (induced B) (III), and BAFF-in- 10. Further analysis by ELISA revealed significantly reduced duced wild-type CD1dhiCD5+ B cells pretreated with anti–IL-10 mAb (200 http://www.jimmunol.org/ levels of IFN-g in the supernatant of cocultured T cells with ng/ml) at a ratio of 1:1 for 72 h (IV). T cell proliferation was evaluated by wild-type CD1dhiCD5+B cells (Fig. 4B). flow cytometry. Results represent four independent experiments. B, ELISA To further ascertain a regulatory role of BAFF-induced B determinants of IFN-g secretion in the supernatant from above cocultures (n = 8) were shown (mean 6 SEM; *p , 0.05). C, Purified BAFF-induced cells in a mouse model of CIA, we i.v. transferred BAFF- hi + 3 5 2/2 hi + CD1d CD5 B cells (5 10 cells) from wild-type or IL-10 mice were induced CD1d CD5 B cells from both wild-type and IL- i.v. transferred into immunized mice on the day of second immunization. 2/2 3 5 10 mice (5 10 ) into DBA/1J mice on the day of Control CIA mice were left untreated. The incidence of arthritis development second immunization with CII/IFA. Notably, only 60% of in immunized mice were monitored and compared by statistical analysis using hi + , mice treated with wild-type CD1d CD5 B cells developed the Fisher’s exact test (p 0.05). D, Serum levels of CII-specific autoanti- by guest on September 24, 2021 bodies in normal DBA/1J, control CIA, wild-type CD1dhiCD5+ B cell- arthritis as compared with 100% in control CIA mice (Fig. 2 2 transferred CIA, and IL-10 / CD1dhiCD5+ B cell-transferred CIA mice 4C). Moreover, an average of 10-d delay in arthritis onset was 6 observed in CIA mice following B cell transfer. However, were measured by ELISA. Values are the mean SEM derived from six mice 2 2 per group (**p , 0.01). transfer of CD1dhiCD5+ B cells from IL-10 / mice showed no protective effect on CIA development. As shown in Fig. 4D, serum levels of anti-CII Abs were significantly reduced in production (19). Consistent with a recognized function for wild-type CD1dhiCD5+ B cells-treated CIA mice. Further TACI in controlling T cell-independent B cell Ab responses, histological examination revealed markedly reduced joint we have detected a unique pattern of BAFF receptors on MZ pathology in mice treated with transferred B cells (data not B cells with high levels of TACI expression when compared shown). with FO B cells (20). Thus, it is possible that the expression pattern of BAFF receptors on MZ B cells might be closely Discussion implicated in mediating BAFF signaling effect on IL-10 in- Extensive studies have established a critical role of BAFF in duction. BAFF may lead to an expansion of IL-10–producing driving T2 B cell differentiation into FO B cells, post-GC B B cell subpopulation by several potential mechanisms, in- cell maturation, plasma cell generation, and Ab production cluding differentiation of regulatory B cells or BAFF-induced (17). In this study, we provide new evidence that exogenous proliferation or survival of a proliferating subpopulation of BAFF at low concentrations can preferentially induce IL-10 IL-10–producing B cells. Our current data do not rule out the production in MZ B cells. As a key regulator of B cell mat- latter possibilities. uration and function, BAFF interacts with three receptors Numerousstudieshavedemonstratedthattherapidactivation (BR3, BCMA, and TACI) expressed on B cells (17). BR3 and of MZ B cells is responsible for the early Ab response to blood- TACI differ significantly in their requirements for ligand borne pathogens (21). Although MZ B cells have been shown to oligomerization for transmitting BAFF signaling, whereas possess the capacity of directly priming naive CD4+ T cells and BAFF levels can further affect whether TACI delivers either driving their differentiation into effector T cells, it has become a positive or negative signal for B cell activation (18). Alter- clear that functional interaction of MZ B cells with dendritic natively, the strong signals mediated by high doses of BAFF cells (DCs) during a T-independent Ab response is critically may predominantly activate the BR3-ligation–mediated mediated by DC-produced BAFF in a CD40-CD40L–in- nonclassical NF-kB2 pathway and lead to the transcription of dependent manner (22). Our current data indicate that BAFF at antiapoptotic factor Bcl-2 for MZ B cell differentiation into low doses can induce IL-10 production in MZ B cells possibly plasma cells by overriding its effect on inducing cytokine via the direct activation of several transcription factors for the The Journal of Immunology 3325

IL-10 gene. Because MZ B cells are anatomically surrounded by agonistic anti-CD40 is an efficacious strategy for the generation of induced regulatory T2-like B cells and for the suppression of lupus in MRL/lpr mice. J. Immunol. BAFF-producing DCs and macrophages in vivo, future studies 182: 3492–3502. would provide new insight in understanding the role of BAFF in 7. Yanaba, K., J. D. Bouaziz, K. M. Haas, J. C. Poe, M. Fujimoto, and T. F. Tedder. 2008. A regulatory B cell subset with a unique CD1dhiCD5+ phenotype controls T regulating MZ B cell function. cell-dependent inflammatory responses. Immunity 28: 639–650. Although BAFF has been generally considered as a driving 8. Yanaba, K., J. D. Bouaziz, T. Matsushita, T. Tsubata, and T. F. Tedder. 2009. The factor for its proinflammatory function, we have demonstrated development and function of regulatory B cells expressing IL-10 (B10 cells) requires antigen receptor diversity and TLR signals. J. Immunol. 182: 7459–7472. that BAFF induces MZ B cell differentiation into IL-10– 9. Mizoguchi, A., and A. K. Bhan. 2006. A case for regulatory B cells. J. Immunol. 176: producing B cells with a regulatory function both in vitro and 705–710. 10. Bouaziz, J. D., K. Yanaba, and T. F. Tedder. 2008. Regulatory B cells as inhibitors in vivo. These findings support the notion that BAFF plays of immune responses and inflammation. Immunol. Rev. 224: 201–214. a dual role in modulating B cell maturation and function. 11. Schiemann, B., J. L. Gommerman, K. Vora, T. G. Cachero, S. Shulga-Morskaya, + hi M. Dobles, E. Frew, and M. L. Scott. 2001. An essential role for BAFF in the Our data show that CD5 CD1d B cells isolated from normal development of B cells through a BCMA-independent pathway. Science 293: BAFF-treated culture can suppress autoimmunity in an IL- 2111–2114. 10–dependent fashion. However, the data do not address 12. Schneider, P., H. Takatsuka, A. Wilson, F. Mackay, A. Tardivel, S. Lens, T. G. Cachero, D. Finke, F. Beermann, and J. Tschopp. 2001. Maturation of marginal whether BAFF-dependent signals in vivo are necessary to in- zone and follicular B cells requires B cell activating factor of the tumor necrosis duce the suppressive activity of these cells. Further studies are factor family and is independent of B cell maturation antigen. J. Exp. Med. 194: 1691–1697. warranted to determine whether increased BAFF expression is 13. Walters, S., K. E. Webster, A. Sutherland, S. Gardam, J. Groom, D. Liuwantara, E. involved in the expansion of IL-10–producing regulatory B Marinõ, J. Thaxton, A. Weinberg, F. Mackay, et al. 2009. Increased CD4+Foxp3+ T cells in BAFF-transgenic mice suppress T cell effector responses. J. Immunol. 182: cells under autoimmune conditions and to validate the po- 793–801. Downloaded from tential application of regulatory B cells as a novel cellular 14. Lo, C. K., Q. L. Lam, L. Sun, S. Wang, K. H. Ko, H. Xu, C. Y. Wu, B. J. Zheng, therapy for the treatment of human autoimmune diseases. and L. Lu. 2008. Natural killer cell degeneration exacerbates experimental arthritis in mice via enhanced interleukin-17 production. Arthritis Rheum. 58: 2700–2711. 15. Lai Kwan Lam, Q., O. King Hung Ko, B. J. Zheng, and L. Lu. 2008. Local BAFF gene silencing suppresses Th17-cell generation and ameliorates autoimmune ar- Disclosures thritis. Proc. Natl. Acad. Sci. USA 105: 14993–14998. 16. Zhang, M., K. H. Ko, Q. L. Lam, C. K. Lo, G. Srivastava, B. Zheng, Y. L. Lau, and The authors have no financial conflicts of interest. L. Lu. 2005. Expression and function of TNF family member B cell-activating http://www.jimmunol.org/ factor in the development of autoimmune arthritis. Int. Immunol. 17: 1081–1092. 17. Mackay, F., P. Schneider, P. Rennert, and J. Browning. 2003. BAFF AND APRIL: References a tutorial on B cell survival. Annu. Rev. Immunol. 21: 231–264. 1. Harris, D. P., L. Haynes, P. C. Sayles, D. K. Duso, S. M. Eaton, N. M. Lepak, L. L. 18. Mackay, F., and P. Schneider. 2008. TACI, an enigmatic BAFF/APRIL receptor, Johnson, S. L. Swain, and F. E. Lund. 2000. Reciprocal regulation of polarized with new unappreciated biochemical and biological properties. Cytokine Growth cytokine production by effector B and T cells. Nat. Immunol. 1: 475–482. Factor Rev. 19: 263–276. 2. Wolf, S. D., B. N. Dittel, F. Hardardottir, and C. A. Janeway, Jr. 1996. Experi- 19. Enzler, T., G. Bonizzi, G. J. Silverman, D. C. Otero, G. F. Widhopf, A. Anzelon- mental autoimmune encephalomyelitis induction in genetically B cell-deficient Mills, R. C. Rickert, and M. Karin. 2006. Alternative and classical NFkB signaling mice. J. Exp. Med. 184: 2271–2278. retain autoreactive B cells in the splenic marginal zone and result in lupus-like 3. Fillatreau, S., C. H. Sweenie, M. J. McGeachy, D. Gray, and S. M. Anderton. 2002. disease. Immunity 25: 403–415. B cells regulate autoimmunity by provision of IL-10. Nat. Immunol. 3: 944–950. 20. Mantchev, G. T., C. S. Cortesaõ, M. Rebrovich, M. Cascalho, and R. J. Bram.

4. Mauri, C., D. Gray, N. Mushtaq, and M. Londei. 2003. Prevention of arthritis by 2007. TACI is required for efﬁcient plasma cell differentiation in response to T- by guest on September 24, 2021 interleukin 10-producing B cells. J. Exp. Med. 197: 489–501. independent type 2 antigens. J. Immunol. 179: 2282–2288. 5. Evans, J. G., K. A. Chavez-Rueda, A. Eddaoudi, A. Meyer-Bahlburg, D. J. 21. Lopes-Carvalho, T., and J. F. Kearney. 2004. Development and selection of mar- Rawlings, M. R. Ehrenstein, and C. Mauri. 2007. Novel suppressive function of ginal zone B cells. Immunol. Rev. 197: 192–205. transitional 2 B cells in experimental arthritis. J. Immunol. 178: 7868–7878. 22. Bala´zs, M., F. Martin, T. Zhou, and J. Kearney. 2002. Blood dendritic cells interact 6. Blair, P. A., K. A. Chavez-Rueda, J. G. Evans, M. J. Shlomchik, A. Eddaoudi, D. A. with splenic marginal zone B cells to initiate T-independent immune responses. Isenberg, M. R. Ehrenstein, and C. Mauri. 2009. Selective targeting of B cells with Immunity 17: 341–352.