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Molecular Pathology & Immunology Program
B.S. 1996, Tianjin Medical University
Thesis Advisor: Patricia Fitzgerald-Bocarsly, Ph.D.
Department of Pathology & Laboratory Medicine
Monday, May 3, 2010
MSB C-555, 1:30 P.M.
PDC are considered to be ¡§professional¡¨ type I interferon (IFN) producing cells in that they produce 10-100-fold more IFN-ƒÑ in response to enveloped virus or synthetic TLR7 and 9 agonists than other cell types. We were interested in determining the ability of human pDC to produce IFN-£f in response to enveloped viruses and synthetic Toll-like receptor (TLR) agonists and whether these cells respond to IFN-£f treatment. We found that HSV induced a 10-20-fold increase in both IFN-ƒÜ1 and IFN-ƒÜ2 transcripts in pDC compared with the unstimulated controls. We developed an intracellular flow cytometry assay using antibodies to IFN-ƒÜ1 and -£f2 to assess the expression of IFN-£f protein by pDC. A subset of human pDC were found to express intracellular IFN-£f as well as IFN-ƒÑ after stimulation with HSV, influenza virus, Sendai virus, or AT-2 inactivated HIV-1 as well as a synthetic TLR9 agonist, CpG A, (but not CpGB) and the TLR7 agonist imiquimod, although fewer cells responded with IFN-£f expression than IFN-ƒÑ. By using ELISA assay, the secretion of IFN-ƒÜ by virus-stimulated pDC was found to be time-dependent and cumulative. In order to understand the mechanism of induction of IFN-ƒÜƒnin pDC, a variety of approaches were utilized. First, we found that cross-linking of CD4 and BDCA2 molecules on pDC inhibited HSV-induced IFN-ƒÜ production. Similar to the production of IFN-ƒÑ in pDC, the HSV-induced IFN-ƒÜ production by pDC was found to be mediated through TLR9. The HSV-induced IFN-ƒÜ production was virus-proliferation independent. Exogenous IFN-ƒÑ was not sufficient to induce IFN-ƒÜ production by pDC, indicating virus induced IFN-ƒÜ production of pDC results from the direct stimulation of virus instead of indirect action of endogenous IFN-ƒÑ. Unstimulated and stimulated pDC were found to express high levels of IFN-£f receptor at both the mRNA and protein levels. Moreover, exogenous IFN-£f treatment of pDC (¡§priming¡¨) led to upregulation of the intracellular expression of both IFN-ƒÑ and IFN-£f. In addition, exogenous IFN-£f, like IFN-ƒÑ, was found to inhibit apoptosis of pDC. We conclude that pDC are major producers of IFN-£f in response to viral stimulation and also express receptors for this cytokine. Moreover, these receptors are functional in that IFN-£f has autocrine effects that strengthen the antiviral effect of the pDC by increasing IFN-ƒÑ and IFN-£f production and promoting pDC survival. With a better understanding the production of IFN-£f and its effects on pDC, we can focus on the role of pDC and IFN-£f in the immune system and a variety of diseases, such as AIDS, cancer, autoimmune diseases with the goal to discover new therapeutic strategies to cure these diseases.