参考文献

Langerhans cells (LC) are a unique subset of dendritic cells (DC),present in the epidermis and serving as the first line of defense against pathogens invading the skin. To investigate the role of human LCs in innate immune responses,we examined TLR expression and function of LC-like DCs derived from CD34+ progenitor cells and compared them to DCs derived from peripheral blood monocytes (monocyte-derived DC; Mo-DC). LC-like DCs and Mo-DCs expressed TLR1-10 mRNAs at comparable levels. Although many of the TLR-induced cytokine patterns were similar between the two cell types,stimulation with the TLR3 agonist poly(I:C) triggered significantly higher amounts of the IFN-inducible chemokines CXCL9 (monokine induced by IFN-gamma) and CXCL11 (IFN-gamma-inducible T cell alpha chemoattractant) in LC-like DCs as compared with Mo-DCs. Supernatants from TLR3-activated LC-like DCs reduced intracellular replication of vesicular stomatitis virus in a type I IFN-dependent manner. Finally,CXCL9 colocalized with LCs in skin biopsy specimens from viral infections. Together,our data suggest that LCs exhibit a direct antiviral activity that is dependent on type I IFN as part of the innate immune system. View Publication

Dendritic cells (DCs) are potent mediators of the immune response,and can be activated by exogenous pathogen components. Galectin-1 is a member of the conserved beta-galactoside-binding lectin family that binds galactoside residues on cell surface glycoconjugates. Galectin-1 is known to play a role in immune regulation via action on multiple immune cells. However,its effects on human DCs are unknown. In this study,we show that galectin-1 induces a phenotypic and functional maturation in human monocyte-derived DCs (MDDCs) similar to but distinct from the activity of the exogenous pathogen stimuli,LPS. Immature human MDDCs exposed to galectin-1 up-regulated cell surface markers characteristic of DC maturation (CD40,CD83,CD86,and HLA-DR),secreted high levels of IL-6 and TNF-alpha,stimulated T cell proliferation,and showed reduced endocytic capacity,similar to LPS-matured MDDCs. However,unlike LPS-matured DCs,galectin-1-treated MDDCs did not produce the Th1-polarizing cytokine IL-12. Microarray analysis revealed that in addition to modulating many of the same DC maturation genes as LPS,galectin-1 also uniquely up-regulated a significant subset of genes related to cell migration through the extracellular matrix (ECM). Indeed,compared with LPS,galectin-1-treated human MDDCs exhibited significantly better chemotactic migration through Matrigel,an in vitro ECM model. Our findings show that galectin-1 is a novel endogenous activator of human MDDCs that up-regulates a significant subset of genes distinct from those regulated by a model exogenous stimulus (LPS). One unique effect of galectin-1 is to increase DC migration through the ECM,suggesting that galectin-1 may be an important component in initiating an immune response. View Publication

NK cells express an activating FcR (FcgammaRIIIa) that mediates Ab-dependent cellular cytotoxicity and the production of immune modulatory cytokines in response to Ab-coated targets. IL-21 has antitumor activity in murine models that depends in part on its ability to promote NK cell cytotoxicity and IFN-gamma secretion. We hypothesized that the NK cell response to FcR stimulation would be enhanced by the administration of IL-21. Human NK cells cultured with IL-21 and immobilized IgG or human breast cancer cells coated with a therapeutic mAb (trastuzumab) secreted large amounts of IFN-gamma. Increased secretion of TNF-alpha and the chemokines IL-8,MIP-1alpha,and RANTES was also observed under these conditions. NK cell IFN-gamma production was dependent on distinct signals mediated by the IL-21R and the FcR and was abrogated in STAT1-deficient NK cells. Supernatants derived from NK cells that had been stimulated with IL-21 and mAb-coated breast cancer cells were able to drive the migration of naive and activated T cells in an in vitro chemotaxis assay. IL-21 also enhanced NK cell lytic activity against Ab-coated tumor cells. Coadministration of IL-21 and Ab-coated tumor cells to immunocompetent mice led to synergistic production of IFN-gamma by NK cells. Furthermore,the administration of IL-21 augmented the effects of an anti-HER2/neu mAb in a murine tumor model,an effect that required IFN-gamma. These findings demonstrate that IL-21 significantly enhances the NK cell response to Ab-coated targets and suggest that IL-21 would be an effective adjuvant to administer in combination with therapeutic mAbs. View Publication

Purine nucleoside phosphorylase (PNP) deficiency in humans results in T lymphocytopenia. Forodesine,a potent inhibitor of PNP,was designed based on the transition-state structure stabilized by the enzyme. Previous studies established that forodesine in the presence of deoxyguanosine (dGuo) inhibits the proliferation of T lymphocytes. A phase 1 clinical trial of forodesine in T-cell malignancies demonstrated significant antileukemic activity with an increase in intracellular dGuo triphosphate (dGTP). High accumulation of dGTP in T cells may be dependent on the levels of deoxynucleoside kinases. Because B-cell chronic lymphocytic leukemia (B-CLL) cells have high activity of deoxycytidine kinase (dCK),we hypothesized that these lymphocytes would respond to forodesine. This postulate was tested in primary lymphocytes during in vitro investigations. Lymphocytes from 12 patients with CLL were incubated with forodesine and dGuo. These CLL cells showed a wide variation in the accumulation of intracellular dGTP without any effect on other deoxynucleotides. This was associated with DNA damage-induced p53 stabilization,phosphorylation of p53 at Ser15,and activation of p21. The dGTP accumulation was related to induction of apoptosis measured by caspase activation,changes in mitochondrial membrane potential,and PARP cleavage. Based on these data,a phase 2 clinical trial of forodesine has been initiated for CLL patients. View Publication

Natural killer (NK) cells from patients with familial hemophagocytic lymphohistiocytosis because of PRF1 (FHL2,n = 5) or MUNC13-4 (FHL3,n = 8) mutations were cultured in IL-2 prior to their use in various functional assays. Here,we report on the surface CD107a expression as a novel rapid tool for identification of patients with Munc13-4 defect. On target interaction and degranulation,FHL3 NK cells displayed low levels of surface CD107a staining,in contrast to healthy control subjects or perforin-deficient NK cells. B-EBV cell lines and dendritic cell targets reveal the FHL3 NK-cell defect,whereas highly susceptible tumor targets were partially lysed by FHL3 NK cells expressing only trace amounts of Munc13-4 protein. Perforin-deficient NK cells were completely devoid of any ability to lyse target cells. Cytokine production induced by mAb-crosslinking of triggering receptors was comparable in patients and healthy control subjects. However,when cytokine production was induced by coculture with 721.221 B-EBV cells,FHL NK cells resulted in high producers,whereas control cells were almost ineffective. This could reflect survival versus elimination of B-EBV cells (ie,the source of NK-cell stimulation) in patients versus healthy control subjects,thus mimicking the pathophysiologic scenario of FHL. View Publication

Human immunodeficiency virus type 1 (HIV-1) R5 isolates that predominantly use CCR5 as a coreceptor are frequently described as macrophage tropic. Here,we compare macrophage tropism conferred by HIV-1 R5 envelopes that were derived directly by PCR from patient tissue. This approach avoids potentially selective culture protocols used in virus isolation. Envelopes were amplified (i) from blood and semen of adult patients and (ii) from plasma of pediatric patients. The phenotypes of these envelopes were compared to those conferred by an extended panel of envelopes derived from brain and lymph node that we reported previously. Our results show that R5 envelopes vary by up to 1,000-fold in their capacity to confer infection of primary macrophages. Highly macrophage-tropic envelopes were predominate in brain but were infrequent in semen,blood,and lymph node samples. We also confirmed that the presence of N283 in the C2 CD4 binding site of gp120 is associated with HIV-1 envelopes from the brain but absent from macrophage-tropic envelopes amplified from blood and semen. Finally,we compared infection of macrophages,CD4(+) T cells,and peripheral blood mononuclear cells (PBMCs) conferred by macrophage-tropic and non-macrophage-tropic envelopes in the context of full-length replication competent viral clones. Non-macrophage-tropic envelopes conferred low-level infection of macrophages yet infected CD4(+) T cells and PBMCs as efficiently as highly macrophage-tropic brain envelopes. The lack of macrophage tropism for the majority of the envelopes amplified from lymph node,blood,and semen is striking and contrasts with the current consensus that R5 primary isolates are generally macrophage tropic. The extensive variation in R5 tropism reported here is likely to have an important impact on pathogenesis and on the capacity of HIV-1 to transmit. View Publication

Halofuginone,a low molecular weight plant alkaloid,inhibits collagen alpha1 (I) gene expression in several animal models and in patients with fibrotic disease,including scleroderma and graft-versus-host disease. In addition,halofuginone has been shown to inhibit angiogenesis and tumor progression. It was demonstrated recently that halofuginone inhibits transforming growth factor-beta (TGF-beta),an important immunomodulator. The present study was undertaken to explore the effects of halofuginone on activated T cells. Peripheral blood T cells were activated by anti-CD3 monoclonal antibodies in the absence and presence of halofuginone and assessed for nuclear factor (NF)-kappaB activity,production of tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma),T cell apoptosis,chemotaxis,and phosphorylation of p38 mitogen-activated protein kinase (MAPK). A delayed-type hypersensitivity (DTH) model was applied to investigate the effect of halofuginone on T cells in vivo. Preincubation of activated peripheral blood T cells with 10-40 ng/ml halofuginone resulted in a significant dose-dependent decrease in NF-kappaB activity (80% inhibition following incubation with 40 ng halofuginone,P = 0.002). In addition,40 ng/ml halofuginone inhibited secretion of TNF-alpha,IFN-gamma,interleukin (IL)-4,IL-13,and TGF-beta (P textless 0.005). Similarly,halofuginone inhibited the phosphorylation of p38 MAPK and apoptosis in activated T cells (P = 0.0001 and 0.005,respectively). In contrast,T cell chemotaxis was not affected. Halofuginone inhibited DTH response in mice,indicating suppression of T cell-mediated inflammation in vivo. Halofuginone inhibits activated peripheral blood T cell functions and proinflammatory cytokine production through inhibition of NF-kappaB activation and p38 MAPK phosphorylation. It also inhibited DTH response in vivo,making it an attractive immunomodulator and anti-inflammatory agent. View Publication

CD4+CD25+ Tregs regulate immunity,but little is known about their own regulation. We now report that the human 60-kDa heat shock protein (HSP60) acts as a costimulator of human Tregs,both CD4+CD25int and CD4+CD25hi. Treatment of Tregs with HSP60,or its peptide p277,before anti-CD3 activation significantly enhanced the ability of relatively low concentrations of the Tregs to downregulate CD4+CD25- or CD8+ target T cells,detected as inhibition of target T cell proliferation and IFN-gamma and TNF-alpha secretion. The enhancing effects of HSP60 costimulation on Tregs involved innate signaling via TLR2,led to activation of PKC,PI3K,and p38,and were further enhanced by inhibition of ERK. HSP60-treated Tregs suppressed target T cells both by cell-to-cell contact and by secretion of TGF-beta and IL-10. In addition,the expression of ERK,NF-kappaB,and T-bet by downregulated target T cells was inhibited. Thus,HSP60,a self-molecule,can downregulate adaptive immune responses by upregulating Tregs innately through TLR2 signaling. View Publication

We have previously described a novel series of low molecular weight protein tyrosine kinase inhibitors which we named tyrphostins. The characteristic active pharmacophore of these compounds was the hydroxy-cis-benzylidenemalononitrile moiety. In this article we describe three novel groups of tyrphostins: (i) one group has the phenolic moiety of the cis-benzylidenemalononitrile replaced either with other substituted benzenes or with heteroaromatic rings,(ii) another is a series of conformationally constrained derivatives of hydroxy-cis-benzylidenemalononitriles in which the malononitrile moiety is fixed relative to the aromatic ring,and (iii) two groups of compounds in which the position trans to the benzenemalononitrile has been substituted by ketones and amides. Among the novel tyrphostins examined we found inhibitors which discriminate between the highly homologous EGF receptor kinase (HER1) and ErbB2/neu kinase (HER2). These findings may lead to selective tyrosine kinase blockers for the treatment of diseases in which ErbB2/neu is involved. View Publication

SALL4,a human homolog to Drosophila spalt,is a novel zinc finger transcriptional factor essential for development. We cloned SALL4 and its isoforms (SALL4A and SALL4B). Through immunohistochemistry and real-time reverse-transcription-polymerase chain reaction (RT-PCR),we demonstrated that SALL4 was constitutively expressed in human primary acute myeloid leukemia (AML,n = 81),and directly tested the leukemogenic potential of constitutive expression of SALL4 in a murine model. SALL4B transgenic mice developed myelodysplastic syndrome (MDS)-like features and subsequently AML that was transplantable. Increased apoptosis associated with dysmyelopoiesis was evident in transgenic mouse marrow and colony-formation (CFU) assays. Both isoforms could bind to beta-catenin and synergistically enhanced the Wnt/beta-catenin signaling pathway. Our data suggest that the constitutive expression of SALL4 causes MDS/AML,most likely through the Wnt/beta-catenin pathway. Our murine model provides a useful platform to study human MDS/AML transformation,as well as the Wnt/beta-catenin pathway's role in the pathogenesis of leukemia stem cells. View Publication

During hematopoietic differentiation of human embryonic stem cells (hESCs),early hematopoietic progenitors arise along with endothelial cells within the CD34(+) population. Although hESC-derived hematopoietic progenitors have been previously identified by functional assays,their phenotype has not been defined. Here,using hESC differentiation in coculture with OP9 stromal cells,we demonstrate that early progenitors committed to hematopoietic development could be identified by surface expression of leukosialin (CD43). CD43 was detected on all types of emerging clonogenic progenitors before expression of CD45,persisted on differentiating hematopoietic cells,and reliably separated the hematopoietic CD34(+) population from CD34(+)CD43(-)CD31(+)KDR(+) endothelial and CD34(+)CD43(-)CD31(-)KDR(-) mesenchymal cells. Furthermore,we demonstrated that the first-appearing CD34(+)CD43(+)CD235a(+)CD41a(+/-)CD45(-) cells represent precommitted erythro-megakaryocytic progenitors. Multipotent lymphohematopoietic progenitors were generated later as CD34(+)CD43(+)CD41a(-)CD235a(-)CD45(-) cells. These cells were negative for lineage-specific markers (Lin(-)),expressed KDR,VE-cadherin,and CD105 endothelial proteins,and expressed GATA-2,GATA-3,RUNX1,C-MYB transcription factors that typify initial stages of definitive hematopoiesis originating from endothelial-like precursors. Acquisition of CD45 expression by CD34(+)CD43(+)CD45(-)Lin(-) cells was associated with progressive myeloid commitment and a decrease of B-lymphoid potential. CD34(+)CD43(+)CD45(+)Lin(-) cells were largely devoid of VE-cadherin and KDR expression and had a distinct FLT3(high)GATA3(low)RUNX1(low)PU1(high)MPO(high)IL7RA(high) gene expression profile. View Publication

AMP-activated protein kinase (AMPK) is a key sensor and regulator of intracellular and whole-body energy metabolism. We have identified a thienopyridone family of AMPK activators. A-769662 directly stimulated partially purified rat liver AMPK (EC50 = 0.8 microM) and inhibited fatty acid synthesis in primary rat hepatocytes (IC50 = 3.2 microM). Short-term treatment of normal Sprague Dawley rats with A-769662 decreased liver malonyl CoA levels and the respiratory exchange ratio,VCO2/VO2,indicating an increased rate of whole-body fatty acid oxidation. Treatment of ob/ob mice with 30 mg/kg b.i.d. A-769662 decreased hepatic expression of PEPCK,G6Pase,and FAS,lowered plasma glucose by 40%,reduced body weight gain and significantly decreased both plasma and liver triglyceride levels. These results demonstrate that small molecule-mediated activation of AMPK in vivo is feasible and represents a promising approach for the treatment of type 2 diabetes and the metabolic syndrome. View Publication