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We investigated the in vivo role of CD69 by analyzing the susceptibility of CD69-/- mice to tumors. CD69-/- mice challenged with MHC class I- tumors (RMA-S and RM-1) showed greatly reduced tumor growth and prolonged survival compared with wild-type (WT) mice. The enhanced anti-tumor response was NK cell and T lymphocyte-mediated,and was due,at least in part,to an increase in local lymphocytes. Resistance of CD69-/- mice to MHC class I- tumor growth was also associated with increased production of the chemokine MCP-1,diminished TGF-beta production,and decreased lymphocyte apoptosis. Moreover,the in vivo blockade of TGF-beta in WT mice resulted in enhanced anti-tumor response. In addition,CD69 engagement induced NK and T cell production of TGF-beta,directly linking CD69 signaling to TGF-beta regulation. Furthermore,anti-CD69 antibody treatment in WT mice induced a specific down-regulation in CD69 expression that resulted in augmented anti-tumor response. These data unmask a novel role for CD69 as a negative regulator of anti-tumor responses and show the possibility of a novel approach for the therapy of tumors. View Publication

Multiple myeloma (MM) is an incurable plasma cell malignancy characterized by immunosuppression. In this study,we identified factors in patients' bone marrow (BM) sera inhibiting autologous anti-MM immunity and developed an ex vivo strategy for inducing MM-specific cytotoxic T lymphocytes (CTLs). We found that sera from BM of MM patients inhibited induction of dendritic cells (DCs),evidenced by both phenotype and only weak stimulation of T-cell proliferation. Anti-vascular endothelial growth factor (anti-VEGF) and/or anti-interleukin 6 (anti-IL-6) antibodies neutralized this inhibitory effect,confirming that VEGF and IL-6,at least in part,mediate immunosuppression in MM patients. To induce MM-specific CTLs ex vivo,immature DCs were generated by culture of adherent mononuclear cells in medium containing granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 for 5 days and then cocultured with apoptotic MM bodies in the presence of tumor necrosis factor alpha (TNF-alpha) for 3 days to induce their maturation. Autologous BM or peripheral blood mononuclear cells were stimulated weekly with these DCs,and cytotoxicity was examined against the MM cells used to pulse DCs. DCs cultured with apoptotic bodies stimulated significantly greater T-cell proliferation (stimulation index [SI] = 23.2 at a T-DC ratio of 360:1) than T cells stimulated by MM cells only (SI = 5.6),DCs only (SI = 9.3),or MM lysate-pulsed DCs (SI = 13.5). These CTLs from MM patients demonstrated specific cytotoxicity (24.7% at the effector-target [E/T] ratio of 40:1) against autologous primary MM cells. These studies therefore show that CTLs from MM patients can recognize and lyse autologous tumor cells and provide the framework for novel immunotherapy to improve patient outcome in MM. View Publication

Treatment with arsenic trioxide (As(2)O(3)) by inducing apoptosis and partial differentiation of acute promyelocytic leukemia (APL) cells results in clinical remission in APL patients resistant to chemotherapy and all-trans-retinoic acid. As(2)O(3) (iAs(III)) is methylated in the liver to mono- and dimethylated metabolites,including methylarsonic acid,methylarsonous acid,dimethylarsinic acid,and dimethylarsinous acid. Methylated trivalent metabolites that are potent cytotoxins,genotoxins,and enzyme inhibitors may contribute to the in vivo therapeutic effect of iAs(III). Therefore,we compared the potency of iAs(III) and trivalent metabolites using chemical precursors of methylarsonous acid and dimethylarsinous acid to induce differentiation,growth inhibition,and apoptosis. Methylarsine oxide (MAs(III)O) and to a lesser extent iododimethylarsine were more potent growth inhibitors and apoptotic inducers than iAs(III) in NB4 cells,an APL cell line. This was also observed in K562 human leukemia,lymphoma cell lines,and in primary culture of chronic lymphocytic leukemia cells,but not human bone marrow progenitor cells. Apoptosis was associated with greater hydrogen peroxide accumulation and inhibition of glutathione peroxidase activity. MAs(III)O,in contrast to iAs(III),did not induce PML-retinoic acid receptor alpha degradation,or restore PML nuclear bodies or differentiation in NB4 cells. In a cocultivation experiment,hepatoma-derived HepG2 cells,but not NB4 cells,methylate radiolabeled iAs(III). Methylated metabolites released from HepG2 cells are preferentially accumulated by NB4 cells. This experimental model suggests that in vivo hepatic methylation of iAs(III) may contribute to As(2)O(3)-induced apoptosis but not differentiation of APL cells. MAs(III)O as an apoptotic inducer should be considered in the treatment of other hematologic malignancies like lymphoma. View Publication

PURPOSE: Immunotherapy holds promise as a new strategy for the eradication of residual cells in acute myeloid leukaemia (AML). Leukaemic antigen presenting cells (APCs) combining optimal antigen presentation and tumour antigenicity could be used as potent T cell activators. For clinical purposes it is desirable to culture APCs under serum-free conditions. Therefore,we compared morphological,immunophenotypical and functional outcome of the serum-free culture of AML-APCs to their serum-enriched culture. METHODS: AML blasts (n=19) were cultured in the presence of either a cytokine mix or calcium ionophore (CI) for 14 and 2 days,respectively,in FCS-containing medium (FCS),StemSpan serum-free medium (SP) and CellGro serum-free medium (CG). After culture relative yields were calculated and immunophenotypic analysis of APC markers was performed. The mixed leukocyte reaction (MLR) was used to determine T cell stimulating capacity. RESULTS: Serum-free culture of AML-APCs resulted in comparable morphology,relative yields and immunophenotype to serum-enriched culture. By comparing both serum-free media we observed a trend towards a more mature phenotype of CI-cultured AML-APCs in SP. MLR showed that serum-free cultured cells have equal T cell stimulatory capacity in comparison with serum-enriched culture. CONCLUSION: These data show that the serum-free culture of AML-APCs is feasible and that these APCs are comparable to serum-enriched cultured AML-APCs with regard to morphological,immunophenotypical and functional characteristics. These AML-APCs are suitable for the development of active specific immunisation protocols which meet the criteria for good clinical practise (GCP). View Publication

OBJECTIVE: Dysregulation of the apoptotic mechanisms plays a key role in the accumulation of malignant B-chronic lymphocytic leukemia (B-CLL) cells. The transcription nuclear factor (NF)-kappaB is important for cell survival by regulating the expression of anti-apoptotic genes. Several cytokines can modulate leukemic growth and apoptosis in B-CLL. The aim of this study was to determine whether cytokine-mediated regulation of apoptosis occurs via modulation of NF-kappaB activity in peripheral blood mononuclear cells from B-CLL patients. PATIENTS AND METHODS: We evaluated NF-kappaB activity in peripheral blood mononuclear cells from 15 untreated B-CLL patients and 11 controls in resting conditions and in the presence of phorbol-12-myristate-13-acetate (PMA) and different cytokines by electrophoretic mobility shift assay. Apoptosis was studied by spectrophotometric analysis of DNA fragmentation. RESULTS: We found a constitutive high NF-kappaB activity not induced by PMA in B-CLL patients,in contrast with a normal inducible NF-kappaB activity in controls. In B-CLL cultures,addition of interleukin (IL)-4 and IL-13 increased,whereas transforming growth factor (TGF)-beta reduced NF-kappaB activity compared with unstimulated cultures. Accordingly,IL-4 and IL-13 decreased,whereas TGF-beta increased DNA fragmentation compared with unstimulated cultures. IL-13 and IL-4 production was increased,whereas TGF-beta was reduced in PMA-stimulated and unstimulated cultures from B-CLL patients compared with controls. CONCLUSIONS: B-CLL patients have a constitutive high NF-kappaB activity,which is modulated by cytokines. In particular,TGF-beta displays a pro-apoptotic activity,whereas IL-4 and IL-13 have opposite effects. These cytokine alterations could be responsible for a positive autocrine circuit that maintains leukemic cells in a pre-apoptotic state. View Publication

Human immunodeficiency virus type 1 (HIV-1) subtype C viruses with different coreceptor usage profiles were isolated from 29 South African patients with advanced AIDS. All 24 R5 isolates were inhibited by the CCR5-specific agents,PRO 140 and RANTES,while the two X4 viruses and the three R5X4 viruses were sensitive to the CXCR4-specific inhibitor,AMD3100. The five X4 or R5X4 viruses were all able to replicate in peripheral blood mononuclear cells that did not express CCR5. When tested using coreceptor-transfected cell lines,one R5 virus was also able to use CXCR6,and another R5X4 virus could use CCR3,BOB/GPR15,and CXCR6. The R5X4 and X4 viruses contained more-diverse V3 loop sequences,with a higher overall positive charge,than the R5 viruses. Hence,some HIV-1 subtype C viruses are able to use CCR5,CXCR4,or both CXCR4 and CCR5 for entry,and they are sensitive to specific inhibitors of entry via these coreceptors. These observations are relevant to understanding the rapid spread of HIV-1 subtype C in the developing world and to the design of intervention and treatment strategies. View Publication

Human immunodeficiency virus type 1 (HIV-1) impacts the activation state of multiple lineages of hematopoietic cells. Chronic HIV-1 infection among individuals with progressive disease can be associated with increased levels of activated signal transducers and activators of transcription (STATs) in peripheral blood mononuclear cells. To investigate interactions between HIV-1 and CD4(+) cells,activated,phosphorylated STAT proteins in nuclear extracts from lymphocytic and promonocytic cell lines as well as primary monocyte-derived macrophages were measured. Levels of activated STATs increased six- to tenfold in HUT78 and U937 cells within 2 h following exposure to virions. The response to virus was dose-dependent,but kinetics of activation was delayed relative to interleukin-2 or interferon-gamma. Activation of STAT1,STAT3,and STAT5 occurred with diverse viral envelope proteins,independent of coreceptor use or viral replication. Envelope-deficient virions had no effect on STAT activation. Monoclonal antibody engagement of CD4 identified a novel role for CD4 as a mediator in the activation of multiple STATs. Results provide a model for HIV-1 pathogenesis in infected and noninfected hematopoietic cells. View Publication

In humans the majority of endothelial cells (EC) constitutively express MHC class II Ags. We know that in vitro ECs can activate CD45RO(+) B7-independent CD4(+) T cells to proliferate and produce IL-2. The in vivo correlate of this T cell response is not known,and here we have explored whether endothelial expression of MHC class II Ags affects the transendothelial migration of alloreactive CD4(+) CD45RO(+) B7-independent T cells. Alloreactive CD4(+) T cell clones and lines were generated against HLA-DR11,DR13,DR4,and DR1 MHC Ags,and their rates of migration across untreated EC line Eahy.926 (MHC class II negative) or Eahy.926 transfected with CIITA (EahyCIITA) to express DR11 and DR13 were investigated. The migrations of EahyCIITA-specific T cell clones and lines were retarded in a DR-specific manner,and retardation was reversed in the presence of mAb to DR Ag. When investigating the ability of T cells to proliferate in response to EahyCIITA before and after transmigration,migrated cells were still able to proliferate,but the frequency of EahyCIITA-specific cells was much reduced compared with that of nonmigrated cells. The use of fluorescently labeled T cells revealed that specific cells become trapped within the endothelial monolayer. Pretreatment of EahyCIITA with IFN-gamma restored the ability of DR11- or DR13-specific T cells to transmigrate and proliferate,thus abrogating DR-specific retardation. We conclude that cognate interaction between T cells and endothelial MHC class II initiates a stop signal possibly similar to an immunological synapse,but this is overcome in an inflammatory milieu. View Publication

The generation and maintenance of virus-specific CD4(+) T cells in humans are not well understood. We used short in vitro stimulation assays followed by intracellular cytokine staining to characterize the timing,magnitude,and Ag specificity of CD4(+) T cells over the course of primary EBV infection. Lytic and latent protein-specific CD4(+) T cells were readily detected at presentation with acute infectious mononucleosis and declined rapidly thereafter. Responses to BZLF-1,BMLF-1,and Epstein-Barr nuclear Ag-3A were more commonly detected than responses to Epstein-Barr nuclear Ag-1. Concurrent analyses of BZLF-1-specific CD4(+) and CD8(+) T cells revealed differences in the expansion,specificity,and stability of CD4(+) and CD8(+) T cell-mediated responses over time. Peripheral blood EBV load directly correlated with the frequency of EBV-specific CD4(+) T cell responses at presentation and over time,suggesting that EBV-specific CD4(+) T cell responses are Ag-driven. View Publication

Killer immunoglobulin-like receptors (KIR) bind self-major histocompatibility complex class I molecules,allowing natural killer (NK) cells to recognize aberrant cells that have down-regulated class I. NK cells express variable numbers and combinations of highly homologous clonally restricted KIR genes,but uniformly express KIR2DL4. We show that NK clones express both 2DL4 alleles and either one or both alleles of the clonally restricted KIR 3DL1 and 3DL2 genes. Despite allele-independent expression,3DL1 alleles differed in the core promoter by only one or two nucleotides. Allele-specific 3DL1 gene expression correlated with promoter and 5' gene DNA hypomethylation in NK cells in vitro and in vivo. The DNA methylase inhibitor,5-aza-2'-deoxycytidine,induced KIR DNA hypomethylation and heterogeneous expression of multiple KIR genes. Thus,NK cells use DNA methylation to maintain clonally restricted expression of highly homologous KIR genes and alleles. View Publication