Receptor cross-linking on human plasmacytoid dendritic cells leads to the regulation of IFN-alpha production

• Published in: Journal of Immunology 2006-11, Vol.177 (9), p.5829-5839
• Main Authors: Fanning, Stacey L, George, Thaddeus C, Feng, Di, Feldman, Steven B, Megjugorac, Nicholas J, Izaguirre, Alexander G, Fitzgerald-Bocarsly, Patricia
• Format: Article
• Language: English
• Subjects: Antibodies - pharmacology; Antigens, Surface - drug effects; Apoptosis; CD4 Antigens - drug effects; Cross-Linking Reagents - pharmacology; Dendritic Cells - drug effects; Dendritic Cells - immunology; Endocytosis - drug effects; Herpesvirus 1, Human - physiology; Humans; Interferon Regulatory Factor-7 - metabolism; Interferon-alpha - biosynthesis; Interferon-alpha - genetics; Interleukin-3 Receptor alpha Subunit - antagonists & inhibitors; Interleukin-3 Receptor alpha Subunit - drug effects; Lectins, C-Type - antagonists & inhibitors; Lectins, C-Type - drug effects; Membrane Glycoproteins - antagonists & inhibitors; Membrane Glycoproteins - drug effects; Microspheres; Phosphorylation; Receptors, Immunologic - antagonists & inhibitors; Receptors, Immunologic - drug effects; Receptors, Immunologic - metabolism; Receptors, Interleukin-3 - antagonists & inhibitors; Receptors, Interleukin-3 - drug effects; Tyrosine - metabolism
• ISSN: 0022-1767; 1550-6606; 1365-2567
• DOI: 10.4049/jimmunol.177.9.5829

Plasmacytoid dendritic cells (PDC) are the natural type I IFN-producing cells that produce large amounts of IFN-alpha in response to viral stimulation. During attempts to isolate PDC from human PBMC, we observed that cross-linking a variety of cell surface receptors, including blood DC Ag (BDCA)-2, BDCA-4, CD4, or CD123 with Abs and immunobeads on PDC leads to inhibition of IFN-alpha production in response to HSV. To understand the mechanisms involved, a number of parameters were investigated. Cross-linking did not inhibit endocytosis of soluble Ag by PDC. Flow cytometry for annexin V and activated caspase-3 indicated that PDC are not undergoing apoptosis after receptor cross-linking. Cross-linking of CD123, but not the other receptors, caused the up-regulation of costimulatory molecules CD80 and CD86, as well as the down-regulation of CD62L, indicating PDC maturation. Thus, anti-CD123 Ab may be acting similar to the natural ligand, IL-3. Anti-phosphotyrosine Ab, as well as Ab to the IFN regulatory factor, IRF-7, was used in intracellular flow cytometry to elucidate the signaling pathways involved. Tyrosine phosphorylation occurred after cross-linking BDCA-2 and BDCA-4, but not CD4. Cross-linking did not affect IRF-7 levels in PDC, however, cross-linking BDCA-2, BDCA-4, and CD4, but not CD123, inhibited the ability of IRF-7 to translocate to the nucleus. Taken together, these results suggest that cross-linking BDCA-2, BDCA-4, and CD4 on PDC regulates IFN-alpha production at the level of IRF-7, while the decrease in IFN-alpha production after CD123 cross-linking is due to stimulation of the IL-3R and induction of PDC maturation.