Interferons modulate Fc epsilon RI-dependent production of autoregulatory IL-10 by circulating human monocytoid dendritic cells.
BACKGROUND
Immature human blood monocytoid dendritic cells (mDCs) express high-affinity receptors for IgE (Fc epsilon RI), yet their exact function and regulation remain poorly understood.


OBJECTIVE
We sought to characterize Fc epsilon RI-dependent cytokine responses and their regulation in circulating human blood mDCs.


METHODS
Fc epsilon RI-dependent cytokine responses of circulating mDCs were studied by using anti-Fc epsilon RI alpha stimulation. Plasmacytoid dendritic cell (pDC) cross-regulation through Toll-like receptor 9 on these responses was investigated by examining the effects of exogenous IFN-alpha pretreatment and by coculturing pDCs and mDCs stimulated with CpG. Culture supernatants were analyzed by means of ELISA to determine cytokine levels. Cell markers were determined by means of flow cytometry.


RESULTS
mDCs express marked levels of Fc epsilon RI (net mean fluorescence intensity, 196 +/- 49; n = 4). After Fc epsilon RI-dependent activation in mDCs, TNF-alpha (2189 +/- 864 pg/10(6) mDCs, n = 3) levels were upregulated within 4 hours, whereas IL-10 (112 +/- 47 pg/10(6) mDCs, n = 3) levels were detectable only after 24 hours of incubation. After adding IL-10-neutralizing antibody, TNF-alpha Fc epsilon RI-dependent responses were significantly augmented (3903 +/- 197 pg/10(6) mDCs, P < .01, n = 3). Conversely, recombinant IL-10 dose-dependently inhibited Fc epsilon RI-mediated TNF-alpha responses up to 86% +/- 3% (n = 3, P < .001). Pretreatment of mDCs with IFN-alpha (100 U/mL) enhanced Fc epsilon RI-dependent secretion of IL-10 by 3.2-fold (183 +/- 11 pg/10(6) mDCs, n = 4) compared with that seen in untreated cells (57 +/- 33 pg/10(6) mDCs, P < .001, n = 4). In pDC/mDC cocultures pretreated with CpG, Fc epsilon RI-dependent IL-10 secretion by mDCs was similarly augmented by 3-fold.


CONCLUSIONS
Autocrine secretion of IL-10, a critical autoregulator of Fc epsilon RI-dependent proinflammatory responses in mDCs, is cross-regulated by IFN-alpha, a major product of Toll-like receptor 9 responses in pDCs that normally promotes T(H)1 immunity.
Le
Trong
T
Department of Pediatrics, Johns Hopkins Asthma and Allergy Center, Baltimore, MD 21224, USA.
Tversky
Jody
J
Chichester
Kristin L
KL
Bieneman
Anja P
AP
Huang
Shau-Ku
SK
Wood
Robert A
RA
Schroeder
John T
JT
D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000328:Adult; D000998:Antiviral Agents / Q000276:immunology / Q000494:pharmacology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D006801:Humans; D016898:Interferon-alpha / Q000276:immunology / Q000494:pharmacology; D016753:Interleukin-10 / Q000096:biosynthesis / Q000276:immunology* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000276:immunology / Q000494:pharmacology; D017455:Receptors, IgE / Q000276:immunology* / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000276:immunology / Q000494:pharmacology; D051217:Toll-Like Receptor 9 / Q000819:agonists / Q000276:immunology / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
D000276:Adjuvants, Immunologic; D000998:Antiviral Agents; C408982:CPG-oligonucleotide; C508609:IL10 protein, human; D016898:Interferon-alpha; D009838:Oligodeoxyribonucleotides; D017455:Receptors, IgE; D011994:Recombinant Proteins; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10