Virally stimulated plasmacytoid dendritic cells produce chemokines and induce migration of T and NK cells

Abstract

The natural interferon (IFN)-producing cell is now known to be identical to the plasmacytoid dendritic cell (PDC). These are Lin-, CD123+, CD11c-, and human leukocyte antigen-DR+ cells that secrete large amounts of IFN-alpha (1-2 IU/cell) when stimulated by enveloped viruses such as herpes simplex virus. In the current study, we have evaluated chemokine expression by virally stimulated PDC. Up-regulation of mRNA for CCL4, CCL3, CCL5, CCL2, and CXC chemokine ligand (CXCL)10 in herpes simplex virus-stimulated PDC was detected by RNAse protection assays. In contrast, PDC-depleted peripheral blood mononuclear cells did not up-regulate these mRNA species upon viral stimulation. Enzyme-linked immunosorbent assay and/or intracellular flow cytometry confirmed production of these proteins, and studies indicated overlapping production of IFN-alpha and the other cytokines/chemokines by PDC. Endocytosis plays a critical role in chemokine induction, as disruption of the pathway inhibits the response. However, transcription of viral genes is not required for chemokine induction. Autocrine IFN-alpha signaling in the PDC could account for a portion of the CXCL10 and CCL2 production in virally stimulated PDC but was not responsible for the induction of the other chemokines. To evaluate the functional role of the chemokines, chemotaxis assays were performed using supernatants from virally stimulated PDC. Activated T cells and natural killer cells, but not naïve T cells, were preferentially recruited by these PDC supernatants. Migration was subsequently inhibited by addition of neutralizing antibody to CCL4 and CXCL10. We hypothesize that virally induced chemokine production plays a pivotal role in the homing of leukocytes to PDC.

Characterization of Virus-Responsive Plasmacytoid Dendritic Cells in the Rhesus Macaque

“…We also observed HSVinduced upregulation of MIP-1␤/CCL4 expression in macaque PDC (Fig. 8B and D), a finding similar to what we reported earlier for humans (28). Finally, similar to human PDC, macaque PDC expressed intracellular TNF-␣ in response to HSV stimulation (Fig.…”

“…IP-10 (CXCL10) and MIP-1␤ (CCL4) are inflammatory chemokines that chemoattract Th1-polarized T cells and NK cells, respectively. We have previous demonstrated that human PDC produce CXCL10 in response to either IFN-␣ or HSV, whereas HSV but not IFN-␣ induces the expression of CCL4 (28). In the macaque model, utilizing intracellular flow cytometry, we detected significant IP-10/CXCL10 production in HSV-stimulated PDC from 7 of 11 monkeys tested ( Fig.…”

“…PDC produce vast amounts of IFN-␣ (3 to 10 pg/cell or 1 to 2 IU/cell) in response to enveloped viruses such as HSV and Sendai virus (SV), in addition to some bacteria and DNA-containing unmethylated CpG sequences (4,7,15,16,25,41). In addition, PDC have been shown to produce inflammatory chemokines such as macrophage inflammatory protein 1␣ (MIP-1␣) and MIP-1␤, IFNinducible protein 10 (IP-10) and MCP-1 in response to CpG, inactivated influenza virus, CD40L stimulation, and HSV stimulation (28,34), and HSV-stimulated PDC express chemokines that attract both natural killer (NK) cells and activated T cells (28). Depending on the nature of the stimulus they receive, PDC can direct either Th1 or Th2 responses (6,26).…”

Trafficking properties of plasmacytoid dendritic cells in health and disease

“…As mentioned, the potential of PDCs to regulate leukocyte recruitment is mostly related to the ability of these cells to respond to viral infection with high levels of type I IFN production. HSV1-activated PDCs recruit T and NK cells through the production of CXCL9, CXCL10 and CCL4, and CD40-engagement further strengthens this response [78,79]. Exposure of PDCs to HIV-1 surface components triggers the secretion of the CCR5 ligands CCL3 and CCL4, suggesting a role of PDCs in limiting viral spreading [80].…”

Receptor Cross-Linking on Human Plasmacytoid Dendritic Cells Leads to the Regulation of IFN-α Production

“…Initially, PDC were recognized for their role in innate antiviral immunity. However, it is now being revealed that these cells are involved in several aspects of immunity including directing cell trafficking via chemokine production (1,2), acting as accessory cells in B cell Ab production (3,4), and inducing Th1, Th2, or T reg responses, depending on the nature of the stimulation (5)(6)(7). Perhaps the best studied aspect of PDC function is their ability to produce the antiviral cytokine IFN-␣.…”