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J. Biol. Chem., Vol. 283, Issue 39, 26477-26483, September 26, 2008

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Calcium Signaling in Dendritic Cells by Human or Mycobacterial Hsp70 Is Caused by Contamination and Is Not Required for Hsp70-mediated Enhancement of Cross-presentation^*

Henriette Bendz, Boris-Christian Marincek^¶, Frank Momburg^¶, Joachim W. Ellwart, Rolf D. Issels, Peter J. Nelson^||, and Elfriede Noessner¹

From the Institute of Molecular Immunology, Helmholtz Zentrum München, German Research Center for Environmental Health, 81377 München, Germany, the Clinical Cooperation Group of Hyperthermia, Internal Medicine Department III, Klinikum Grosshadern, Ludwig Maximilians University, 81377 München, Germany, the ^¶Division of Molecular Immunology, German Cancer Research Center, 69120 Heidelberg, Germany, and the ^||Medizinische Poliklinik, Ludwig Maximilians University of Munich, 80336 München, Germany

Extracellular heat shock proteins (HSPs) can stimulate antigen-specific immune responses. Using recombinant human (rhu)Hsp70, we previously demonstrated that through complex formation with exogenous antigenic peptides, rhuHsp70 can enhance cross-presentation by antigen-presenting cells (APCs) resulting in stronger T cell stimulation. T cell stimulatory activity has also been described for mycobacterial (myc)Hsp70. MycHsp70-assisted T cell activation has been reported to act through the binding of mycHsp70 to chemokine receptor 5 (CCR5), calcium signaling, phenotypic maturation, and cytokine secretion by dendritic cells (DCs). We report that highly purified rhuHsp70 and mycHsp70 proteins both strongly enhance cross-presentation of exogenous antigens. Augmentation of cross-presentation was seen for different APCs, irrespective of CCR5 expression. Moreover, neither of the purified Hsp70 proteins induced calcium signals in APCs. Instead, calcium signaling activity was found to be caused by contaminating nucleotides present in Hsp70 protein preparations. These results refute the hypothesis that mycHsp70 proteins require CCR5 expression and calcium signaling by APCs for enhanced antigen cross-presentation for T cell stimulation.

Received for publication, April 30, 2008 , and in revised form, July 8, 2008.

^* This work was supported in part by Grants SFB455 (to E. N. and R. D. I.) and SFB-TR36 (to P. J. N.) from the Deutsche Forschungsgemeinschaft and EU Grant INNOCHEM (to P. J. N.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Inst. of Molecular Immunology, Helmholtz Zentrum München-German Research Center for Environmental Health, Marchioninistraβe 25, 81377 München, Germany. Tel.: 49-89-7099303; Fax: 49-89-7099300; E-mail: noessner{at}helmholtz-muenchen.de.

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