Acknowledgments We thank Genentech, South San Francisco, CA, USA for provision of the anti-human TLR2 mAb. References 1. Okamoto M, Oh EG, Oshikawa T, Furuichi S, Tano T, et al. (2004) Toll-like receptor 4 mediates the antitumor host response induced by a 55-kilodalton protein isolated from Aeginetia indica L., a parasitic plant. Clin Diagn Lab Immunol 11: 483–495. 2. Ando I, Tsukumo Y, Wakabayashi T, Akashi S, Miyake K, et al. (2002) Safflower polysaccharides activate the transcription factor NF-kappa B via Toll- like receptor 4 and induce cytokine production by macrophages. Int Immunopharmacol 2: 1155–1162. 3. Han SB, Park SK, Ahn HJ, Yoon YD, Kim YH, et al. (2003) Characterization of B cell membrane receptors of polysaccharide isolated from the root of Acanthopanax koreanum. Int Immunopharmacol 3: 683–691. 4. Han SB, Yoon YD, Ahn HJ, Lee HS, Lee CW, et al. (2003) Toll-like receptor- mediated activation of B cells and macrophages by polysaccharide isolated from cell culture of Acanthopanax senticosus. Int Immunopharmacol 3: 1301–1312. 5. Crotty S, Aubert RD, Glidewell J, Ahmed R (2004) Tracking human antigen- specific memory B cells: a sensitive and generalized ELISPOT system. J Immunol Methods 286: 111–122. 6. Farnes P, Barker BE, Brownhill LE, Fanger H (1964) Mitogenic Activity in Phytolacca Americana (Pokeweed). Lancet 2: 1100–1101. 7. Bekeredjian-Ding I, Inamura S, Giese T, Moll H, Endres S, et al. (2007) Staphylococcus aureus protein A triggers T cell-independent B cell proliferation by sensitizing B cells for TLR2 ligands. J Immunol 178: 2803–2812. 8. Yokoyama K, Terao T, Osawa T (1978) Carbohydrate-binding specificity of pokeweed mitogens. Biochim Biophys Acta 538: 384–396. 9. Yokoyama K, Yano O, Terao T, Osawa T (1976) Purification and biological activities of pokeweek (Phytolacca americana) mitogens. Biochim Biophys Acta 427: 443–452. 10. Yang JS, Kim HJ, Ryu YH, Yun CH, Chung DK, et al. (2006) Endotoxin contamination in commercially available pokeweed mitogen contributes to the activation of murine macrophages and human dendritic cell maturation. Clin Vaccine Immunol 13: 309–313. 11. Bekeredjian-Ding IB, Wagner M, Hornung V, Giese T, Schnurr M, et al. (2005) Plasmacytoid dendritic cells control TLR7 sensitivity of naive B cells via type I IFN. J Immunol 174: 4043–4050. 12. Hornung V, Rothenfusser S, Britsch S, Krug A, Jahrsdorfer B, et al. (2002) Quantitative expression of toll-like receptor 1–10 mRNA in cellular subsets of human peripheral blood mononuclear cells and sensitivity to CpG oligodeox- ynucleotides. J Immunol 168: 4531–4537. 13. Werts C, Tapping RI, Mathison JC, Chuang TH, Kravchenko V, et al. (2001) Leptospiral lipopolysaccharide activates cells through a TLR2-dependent mechanism. Nat Immunol 2: 346–352. 14. Adachi O, Kawai T, Takeda K, Matsumoto M, Tsutsui H, et al. (1998) Targeted disruption of the MyD88 gene results in loss of IL-1- and IL-18- mediated function. Immunity 9: 143–150. 15. Kirschning CJ, Wesche H, Merrill Ayres T, Rothe M (1998) Human toll-like receptor 2 confers responsiveness to bacterial lipopolysaccharide. J Exp Med 188: 2091–2097. PWM-Induced B Cell Activation Author Contributions Conceived and designed the experiments: IB-D KH. Performed the experiments: IB-D SF MP. Analyzed the data: IB-D MP. Contributed reagents/materials/analysis tools: CK. Wrote the paper: IB-D. 16. Bekeredjian-Ding I, Roth SI, Gilles S, Giese T, Ablasser A, et al. (2006) T cell- independent, TLR-induced IL-12p70 production in primary human monocytes. J Immunol 176: 7438–7446. 17. Bernasconi NL, Onai N, Lanzavecchia A (2003) A role for Toll-like receptors in acquired immunity: up-regulation of TLR9 by BCR triggering in naive B cells and constitutive expression in memory B cells. Blood 101: 4500–4504. 18. Bekeredjian-Ding I, Jego G (2009) Toll-like receptors–sentries in the B-cell response. Immunology 128: 311–323. 19. Hou B, Saudan P, Ott G, Wheeler ML, Ji M, et al. (2011) Selective utilization of Toll-like receptor and MyD88 signaling in B cells for enhancement of the antiviral germinal center response. Immunity 34: 375–384. 20. Roberts TL, Turner ML, Dunn JA, Lenert P, Ross IL, et al. (2011) B cells do not take up bacterial DNA: an essential role for antigen in exposure of DNA to toll- like receptor-9. Immunol Cell Biol. 21. Heeg K, Dalpke A, Peter M, Zimmermann S (2008) Structural requirements for uptake and recognition of CpG oligonucleotides. Int J Med Microbiol 298: 33–38. 22. Ruprecht CR, Lanzavecchia A (2006) Toll-like receptor stimulation as a third signal required for activation of human naive B cells. Eur J Immunol 36: 810–816. 23. Kilpatrick DC, Graham C, Urbaniak SJ (1986) Inhibition of human lymphocyte transformation by tomato lectin. Scand J Immunol 24: 11–19. 24. De Castro C, Molinaro A, Lanzetta R, Silipo A, Parrilli M (2008) Lipopolysaccharide structures from Agrobacterium and Rhizobiaceae species. Carbohydr Res 343: 1924–1933. 25. Dalpke A, Frank J, Peter M, Heeg K (2006) Activation of toll-like receptor 9 by DNA from different bacterial species. Infect Immun 74: 940–946. 26. Fujii T, Hayashida M, Hamasu M, Ishiguro M, Hata Y (2004) Structures of two lectins from the roots of pokeweed (Phytolacca americana). Acta Crystallogr D Biol Crystallogr 60: 665–673. 27. Sasso EH, Silverman GJ, Mannik M (1989) Human IgM molecules that bind staphylococcal protein A contain VHIII H chains. J Immunol 142: 2778–2783. 28. Avalos AM, Latz E, Mousseau B, Christensen SR, Shlomchik MJ, et al. (2009) Differential cytokine production and bystander activation of autoreactive B cells in response to CpG-A and CpG-B oligonucleotides. J Immunol 183: 6262–6268. 29. Wang Y, Krieg AM (2003) Synergy between CpG- or non-CpG DNA and specific antigen for B cell activation. Int Immunol 15: 223–231. 30. Borjeson J, Reisfeld R, Chessin LN, Welsh PD, Douglas SD (1966) Studies on human peripheral blood lymphocytes in vitro. I. Biological and physicochemical properties of the pokeweed mitogen. J Exp Med 124: 859–872. 31. Chaturvedi A, Dorward D, Pierce SK (2008) The B cell receptor governs the subcellular location of Toll-like receptor 9 leading to hyperresponses to DNA- containing antigens. Immunity 28: 799–809. 32. Eckl-Dorna J, Batista FD (2009) BCR-mediated uptake of antigen linked to TLR9 ligand stimulates B-cell proliferation and antigen-specific plasma cell formation. Blood 113: 3969–3977. PLoS ONE | www.plosone.org 11 January 2012 | Volume 7 | Issue 1 | e29806