Effect of cytofectins on the immune response of murine macrophages to mammalian DNA

Authors

  • Fu-Gang Zhu,

    1. Medical Research Service, Durham Veterans Administration Hospital and Division of Rheumatology, Allergy and Clinical Immunology, Departments of Medicine and Immunology, Duke University Medical Center, Durham, NC, USA
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  • Charles F. Reich,

    1. Medical Research Service, Durham Veterans Administration Hospital and Division of Rheumatology, Allergy and Clinical Immunology, Departments of Medicine and Immunology, Duke University Medical Center, Durham, NC, USA
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  • David S. Pisetsky

    1. Medical Research Service, Durham Veterans Administration Hospital and Division of Rheumatology, Allergy and Clinical Immunology, Departments of Medicine and Immunology, Duke University Medical Center, Durham, NC, USA
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Dr David S. Pisetsky, Durham VA Medical Center, 508 Fulton Street, PO Box 151G, Durham, NC 27705, USA. E-mail: dpiset@acpub.duke.edu

Summary

DNA, depending on base sequence, can induce a wide range of immune responses. While bacterial DNA is stimulatory, mammalian DNA is inactive alone and can, moreover, inhibit the response to bacterial DNA. To determine whether the mode of cell entry affects the immune properties of mammalian DNA, we have investigated the effects of the cytofectin agents Fugene 6 (Roche Diagnostics Corp., Indianapolis, IN), Lipofectin and Lipofectamine (Life Technologies, Grand Island, NY) on the responses of murine macrophages to DNA from calf thymus and human placenta. Whereas calf thymus and human placenta DNA alone failed to stimulate J774 or RAW264·7 cell lines or bone marrow-derived macrophages, these DNAs in complexes with cytofectin agents stimulated macrophages to produce nitric oxide but not interleukin 12. Both single-stranded and double-stranded DNAs were active in the presence of cytofectins. Macrophage activation by the DNA–cytofectin complexes was reduced by chloroquine, suggesting a role of endosomal acidification in activation. As shown by flow cytometry and confocal microscopy, the cytofectins caused an increase in the uptake of DNA into cells. Our findings indicate that macrophages vary in their response to DNA depending on uptake pathway, suggesting that activation by DNA reflects not only sequence but also context or intracellular location.

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