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.
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.
Bendz
Henriette
H
Institute of Molecular Immunology, Helmholtz Zentrum München, German Research Center for Environmental Health, 81377 München, Germany.
Marincek
Boris-Christian
BC
Momburg
Frank
F
Ellwart
Joachim W
JW
Issels
Rolf D
RD
Nelson
Peter J
PJ
Noessner
Elfriede
E
D017951:Antigen Presentation / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology*; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology*; D009711:Nucleotides / Q000276:immunology*; D011485:Protein Binding / Q000276:immunology; D019713:Receptors, CCR5 / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*
D001426:Bacterial Proteins; D018840:HSP70 Heat-Shock Proteins; C444642:HSP70 protein, Mycobacterium tuberculosis; D009711:Nucleotides; D019713:Receptors, CCR5; D011994:Recombinant Proteins