Regulatory T (Treg) cells act as terminators of T cell immuniy during acute phase of viral infection; however, their role and suppressive mechanism in chronic viral infection are not completely understood. In this study, we compared the phenotype and function of Treg cells during acute or chronic infection with lymphocytic choriomeningitis virus. Chronic infection, unlike acute infection, led to a large expansion of Treg cells and their upregulation of programmed death-1 (PD-1). Treg cells from chronically infected mice (chronic Treg cells) displayed greater suppressive capacity for inhibiting both CD8+ and CD4+ T cell proliferation and subsequent cytokine production than those from naive or acutely infected mice. A contact between Treg and CD8+ T cells was necessary for the potent suppression of CD8+ T cell immune response. More importantly, the suppression required cell-specific expression and interaction of PD-1 on chronic Treg cells and PD-1 ligand on CD8+ T cells. Our study defines PD-1 upregulated on Treg cells and its interaction with PD-1 ligand on effector T cells as one cause for the potent T cell suppression and proposes the role of PD-1 on Treg cells, in addition to that on exhausted T cells, during chronic viral infection.

This paper presents a circulating tumor cell (CTC) microseparator for isolation of CTCs from human peripheral blood using immunomagnetic nanobeads with bound antiepithelial cell adhesive molecule (EpCAM) antibodies that specifically bind to epithelial cancer cells. The isolation is performed through lateral magnetophoresis, which is induced by high-gradient magnetic separation technology, involving a ferromagnetic wire array inlaid in the bottom substrate of a microchannel. Experimental results showed that the CTC microseparator isolates about 90% of spiked CTCs in human peripheral blood at a flow rate of up to 5 mL/h and purifies to approximately 97%. The overall isolation procedure was completed within 15 min for 200 μL of peripheral blood. CTCs from peripheral blood of patients with breast and lung cancers were isolated with the CTC microseparator, and the results were compared with those of healthy donors. Using a fluorescence-based viability assay, the viability of CTCs isolated from peripheral blood of patients with cancer was observed. In addition, the usefulness of the CTC microseparator for subsequent genetic assay was confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR) amplification of cancer-specific genes using CTCs isolated from patients with cancer.

Background and purpose:Cilostazol is a specific inhibitor of 3′-5′-cyclic adenosine monophosphate (cAMP) phosphodiesterase, which is widely used to treat ischemic symptoms of peripheral vascular disease. Although cilostazol has been shown to exhibit vasodilator properties as well as antiplatelet and anti-inflammatory effects, its cellular mechanism in microglia is unknown. In the present study, we assessed the anti-inflammatory effect of cilostazol on the production of pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated murine BV2 microglia. Experimental approach: We examined the effects of cilostazol on LPS-induced nuclear factor-kappaB (NF-kB) activation and phosphorylation of mitogen-activated protein kinases (MAPKs). Key results: Cilostazol suppressed production of nitric oxide (NO), prostaglandin E2 (PGE2) and the proinflammatory cytokines, interleukin-1 (IL-1), tumour necrosis factor-a, and monocyte chemoattractant protein-1 (MCP-1), in a concentrationdependent manner. Inhibitory effects of cilostazol were not affected by treatment with an adenylate cyclase inhibitor, SQ 22536, indicating that these actions of cilostazol were cAMP-independent. Cilostazol significantly inhibited the DNA binding and transcriptional activity of NF-kB. Moreover, cilostazol blocked signalling upstream of NF-kB activation by inhibiting extracellular signal-regulated kinases 1 and 2 (ERK1/2) and c-Jun N-terminal kinase (JNK), but without affecting the activity of p38 MAPK. Conclusion and implications:Our results demonstrate that suppression of the NF-kB, ERK, JNK signalling pathways may inhibit LPS-induced NO and PGE2 production. Therefore, cilostazol may have therapeutic potential for neurodegenerative diseases by inhibiting pro-inflammatory mediators and cytokine production in activated microglia. (2010) 159, 1274-1285; doi:10.1111/j.1476-5381.2009.00615.x; published online 28 January 2010 British Journal of PharmacologyKeywords: cilostazol; inducible nitric oxide synthase; cyclooxygenase-2; nuclear factor-kB; monocyte chemoattractant protein-1; cAMP Abbreviations: COX-2, cyclooxygenase-2; IKK, IkB kinase; IL-1b, interleukin-1b; iNOS, inducible nitric oxide synthase; IkB, inhibitor of NF-kB; MAPK, mitogen-activated protein kinase; MCP-1, monocyte chemoattractant protein-1; MEKK1, MAPK/ERK kinase kinase 1; NF-kB, nuclear factor-kB; PGE2, prostaglandin E2; SEK1/MKK4, SAPK/ERK1/ MAPK kinase kinase 4; TNF-a, tumour necrosis factor-a

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B7 homolog 1 (B7-H1)-expressing myeloma cells not only inhibit myeloma-specific cytotoxic T lymphocytes (CTL), but also confer a proliferative advantage: resistance to antimyeloma chemotherapy. However, it remains unknown whether B7-H1 expressed on myeloma cells induces cellular responses associated with aggressive myeloma behaviors. To address this question, we analyzed the proliferation and drug sensitivity of B7-H1-expressing myeloma cells transfected with B7-H1-specific short-hairpin RNA or treated with programmed cell death (PD)-1-Fc-coupled beads. Knockdown of B7-H1 expression in myeloma cells significantly inhibited cell proliferation and increased apoptosis induced by the chemotherapeutic alkylating agent melphalan, with downregulation of the expression of cell cycle-related genes (CCND3 and CDK6) and antiapoptotic genes (BCL2 and MCL1). B7-H1 molecules thus contributed to myeloma cell-cycle progression and suppression of drug-induced apoptosis. B7-H1-expressing myeloma cells had a higher affinity for PD-1 than for CD80. PD-1-Fc beadtreated myeloma cells also became resistant to apoptosis that was induced by melphalan and the proteasome inhibitor bortezomib. Apoptosis resistance was associated with the PI3K/AKT pathway. Both myeloma cell drug resistance and antiapoptotic responses occurred through the PI3K/AKT signaling pathway, initiated from "reverse" stimulation of B7-H1 by PD-1. Therefore, B7-H1 itself may function as an oncogenic protein in myeloma cells. The interaction between B7-H1 on myeloma cells and PD-1 molecules not only inhibits tumorspecific CTLs but also induces drug resistance in myeloma cells through the PI3K/AKT signaling pathway. These observations provide mechanistic insights into potential immunotherapeutic benefits of blocking the B7-H1-PD-1 pathway.