Fas 670 promoter polymorphism is associated to susceptibility, clinical presentation, and survival in adult T cell leukemia.

Fas (TNFRSF6/Apo-1/CD95) is a type I transmembrane receptor, which mediates apoptosis. Fas gene mutations, aberrant transcripts, and abundant expression of Fas have been reported in adult T cell leukemia (ATL). To further elucidate the role of Fas in ATL pathogenesis, we investigated whether the -670 FAS promoter A/G polymorphism (STAT1-binding site) might contribute to susceptibility and clinical outcome in ATL. Thirty-one patients with ATL, 33 healthy, human T lymphotropic virus type 1-infected individuals, and 70 healthy, uninfected controls were genotyped for the FAS -670 polymorphism by PCR-restriction fragment-length polymorphism. The AA genotype was significantly over-represented in ATL patients in comparison with healthy controls (P=0.006), as well as asymptomatics (P=0.037), corresponding to an odds ratio (OR) of 3.79 [95% confidence intervals (CI; 1.28-11.41)] and 4.58 [95% CI (1.13-20.03)], respectively. The AA group also comprised significantly more aggressive (acute and lymphoma) clinical subtypes [P=0.012; OR=8.40; 95% CI (1.60-44.12)]. In addition, we observed a statistically significant association between GG genotype and survival (log rank test, P=0.032). Finally, IFN-gamma-induced but not basal FAS mRNA levels were increased significantly (P=0.049) in PBMCs from AA versus GG individuals, demonstrating the IFN-dependent functionality of the -670 polymorphism. In conclusion, our results demonstrate that a functional Fas promoter polymorphism is significantly associated to susceptibility, clinical manifestation, and survival in ATL.

Treatment of multiple sclerosis patients with interferon-beta primes monocyte-derived macrophages for apoptotic cell death.

Although interferon (IFN)-beta has shown a significant clinical benefit in multiple sclerosis (MS), its mechanism of action remains unclear. We found that IFN-beta treatment of patients with MS resulted in a significant increase in apoptotic cell death (measured by annexin V staining and nuclear fragmentation) of monocyte-derived macrophages, as compared with cells derived from patients before treatment. Stimulation of the cells with IFN-beta in vitro resulted in an even further increase of annexin V binding, as well as increased Fas (CD 95, APO-1) expression. However, no increased Fas expression, apoptotic monocytes, or monocytopenia were observed upon in vivo treatment. This indicates that IFN-beta does not deliver a death signal to monocytes but rather primes for subsequent macrophage apoptosis upon activation or differentiation.

HIV-1 p17 and IFN-gamma both induce fructose 1,6-bisphosphatase.

The p17 matrix protein of the human immunodeficiency virus type 1 (HIV-1) plays a crucial role in AIDS pathogenesis. It orchestrates viral assembly and directs the preintegration complex to the nucleus of infected cells. Recently, the three-dimensional structure of p17 was shown to resemble that of interferon-gamma (IFN-gamma), suggesting that both proteins might share analogous functions. We demonstrate that in monocytes, p17 shares with IFN-gamma the ability to induce 1alpha-hydroxylase activity and to activate fructose 1,6-bisphosphatase gene expression in the presence of 25-hydroxyvitamin D3. However, p17 does not bind to the IFN-gamma cell membrane receptor and fails to increase expression of IFN-gamma-induced proteins, such as tryptophanyl-tRNA synthetase, Fc gammaRI, and HLA DR or B7/BB1 antigens. Altogether, our results raise the possibility that the structural resemblance between p17 and IFN-gamma causes the selective activation of a common pathway resulting in the production of 1,25-dihydroxyvitamin D3. We also found that unlike IFN-gamma, p17 increases the intracellular ATP content. Since transport of the HIV-1 preintegration complex through the nuclear membrane is an ATP-dependent process, our observation suggests that p17 plays a double role in this active transport, not only by acting as a chaperone molecule but also by recruiting the necessary energy for this process.

Synergistic effect of prolactin on IFN-gamma-mediated growth arrest in human monoblastic cells: correlation with the up-regulation of IFN-gamma receptor gene expression.

Interferon-gamma (IFN-gamma) stimulates the development of monocytic features in human myeloid precursors. Because transcriptional regulation of IFN-gamma and the pituitary hormone prolactin (PRL) has been described to involve common Jak-STAT pathways, we addressed here the question of whether PRL plays a role in monoblastic (U937) cell growth and macrophage maturation. In contrast to IFN-gamma, PRL did not affect U937 cell growth nor induction of differentiation as assessed by the unchanged cell surface expression of maturation markers CD11b and HLA-DR class II. However, PRL in synergy with IFN-gamma inhibited, in a time- and dose-dependence, proliferation of U937 cells without influencing their maturation induced by IFN-gamma. IFN-gamma and PRL both affected the expression of the IFN-gamma receptor (IFN-gamma R) gene by increasing IFN-gamma R mRNA levels. The rise in IFN-gamma R transcripts was accompanied by a low but significant release of IL-6 which has previously been shown to stabilize IFN-gamma R mRNA. Moreover, a transient increase in surface expression of IFN-gamma R was observed in U937 cells treated by IFN-gamma alone or in combination with PRL, whereas no apparent modulation of cell surface IFN-gamma R was observed in cells treated with PRL. Lastly, PRL did not induce transcriptional activation in IFN-gamma inducible IRF-1 and Fc gamma RI genes in U937 cells. Together, our data indicate that IL-6 secretion and increased expression of the IFN-gamma R gene correlate with U937 cell growth arrest induced by IFN-gamma and PRL, probably through a signaling mechanism which does not involve the Stat 1/IRF-1 pathway.

IFN-beta and TGF-beta differentially regulate IL-12 activity in human peripheral blood mononuclear cells.

Both IFN-beta and TGF-beta have demonstrated their ability to antagonize several of the stimulatory activities of IFN-gamma on human macrophages, thereby classifying them as Th2-like. Aiming at a further characterization of their role in Th1/Th2 development, we studied their possible interaction with IL-12, the key Th1 cytokine. We found that IFN-beta by itself induced modest amounts of IFN-gamma, but was able to synergize with IL-12 for IFN-gamma induction. TGF-beta, on the other hand, had no effect by itself and inhibited significantly the IL-12-induced IFN-gamma secretion. The differential effect of IFN-beta and TGF-b on IL-12 bioactivity was most pronounced upon IFN-gamma synthesis, since IFN-beta induced only marginal amounts of IL-10 and IL-12 and TGF-beta diminished constitutive IL-10 production, while neither had a significant effect on TNF-alpha production. Although monocytes did not produce detectable IFN-gamma with any of the stimuli, adherent cells were found to cooperate with non-adherent lymphocytes for maximal IFN-gamma production. However, IL-18, a monocyte-derived IFN-gamma-inducing cytokine able to synergize with IL-12, was undetectable in IFN-beta or IFN-beta+IL-12-stimulated cells. In conclusion, the ability of IFN-beta to synergize with IL-12 for IFN-gamma synthesis, without significant concomitant IL-10 production, suggest a strong boost to Th1 development, which seems to be IL-18-independent.

Biological characterization and chemokine receptor usage of HIV type 1 isolates prevalent in Brazil.

The human immunodeficiency virus type 1 (HIV-1), the etiological agent of the acquired immunodeficiency syndrome (AIDS), shows a variety of biological properties, which may constitute an obstacle to development of effective vaccines or antiretroviral therapy. To characterize Brazilian strains of HIV-1, we studied 24 viruses isolated from blood samples of HIV-1-positive patients from different regions of the country. To examine the cell tropism and the virus ability to form syncytia, primary macrophages and the CD4+ T cell line MT-2 were infected with these viruses. We found that 22 isolates replicated well in macrophages (macrophage-tropic isolates), 2 infected only MT-2 cells (T cell line tropic variants), while 6 of them grew in both cells. We found 8 syncytium-inducing (SI) and 16 non-SI (NSI) isolates. Continuous cultures of 18 isolates were established in the CCR5+/CXCR4+ cell line PM-1, and SI/NSI features of these viruses were confirmed by cell fusion assay with uninfected CD4+ T cell lines (PM-1, MT-2, H9, and SUP-T1). The coreceptor usage of 18 isolates was investigated by infecting U87 cells transfected with CD4 and chemokine receptors, and we found that 11 isolates infected only CCR5+ cells, 3 only CXCR4+ cells, whereas 4 used both coreceptors. We also observed that X4 isolates were more sensitive to neutralization by dextran sulfate than R5 or R5X4 viruses. Our findings show that the Brazilian isolates are phenotypically similar to those prevalent in other regions, which could mean that therapeutic strategies based on HIV-1 phenotypic properties would be efficient in Brazil, as in other countries.

Mixed inflammatory/regulatory cytokine profile marked by simultaneous raise of interferon-gamma and interleukin-10 and low frequency of tumour necrosis factor-alpha(+) monocytes are hallmarks of active human visceral Leishmaniasis due to Leishmania chagasi infection.

Considering the complexity of the immunological events triggered during active visceral Leishmaniasis (VL), the relevance of the segregation of the immune response during human VL into type 1 and type 2 still remains unclear. For this purpose, in individuals living in risk areas for VL, we have evaluated especially asymptomatic individuals and patients with active VL, the plasmatic levels of cytokines and reactive nitrogen species under ex vivo conditions. In addition, we have also performed an analysis of intracellular cytokine patterns of circulating leucocytes after short-term culture, particularly in the absence of antigenic-specific stimulation, in order to reflect dynamic events of immune response in vivo during Leishmania chagasi infection. Although asymptomatic individuals and non-infected subjects presented a similar immunological profile, an outstanding inflammatory/regulatory profile, based on higher plasmatic levels of cytokines such as interleukin (IL)-8, interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, IL-6 and IL-10, was associated with clinical status observed in active VL. In this context, we hypothesize that IL-10, through its ability to inhibit anti-leishmanial macrophage activation, associated with the lower frequency of TNF-alpha(+) monocytes and ordinary levels of nitrite and nitrate are the major mechanisms associated with disease onset.

TGF-beta 1-stimulated adhesion of human mononuclear phagocytes to fibronectin and laminin is abolished by IFN-gamma: dependence on alpha 5 beta 1 and beta 2 integrins.

Monocyte migration within the extravascular space of inflamed tissues is controlled by adhesion molecules and inflammatory cytokines. In this study, we analyzed the capacity of TGF-beta 1 and IFN-gamma to regulate adhesion of human activated monocytes to fibronectin (FN) and to laminin (LM), two components of the extracellular matrix. When cultured in the absence of any of these two stimuli, human monocytes underwent "spontaneous activation" and adhered to both FN and LM. Adhesion to FN was inhibited in the presence of alpha 5 and beta 1 integrin blocking antibodies, whereas beta 2 blocking antibody blocked attachment to LM. Exogenous TGF-beta 1 increased the adhesive ability of monocytes to FN and to LM, respectively, linked to the increase of alpha 5 and beta 2 mRNA and protein synthesis levels. Moreover, an increase in alpha 5 expression at the monocyte cell surface was observed. In contrast, monocytes stimulated with exogenous IFN-gamma lost their capacity to bind to FN and this coincided with the down-regulation of surface alpha 5 expression which occurred at the posttranscriptional level of alpha 5 synthesis. Although IFN-gamma-treated monocytes also showed a decreased ability to adhere to LM, no alteration of beta 2 mRNA levels, beta 2 protein synthesis, and beta 2 cell surface expression was detectable, thus suggesting a modification of the functional state of surface beta 2 integrins. Furthermore, when stimulated with TGF-beta 1, IFN-gamma-pretreated monocytes reacquired the ability to bind to FN and LM. Conversely, IFN-gamma reduced adhesiveness to FN and LM of monocytes initially stimulated with TGF-beta 1. These in vitro adhesive-deadhesive responses of monocytes to TGF-beta 1 and IFN-gamma modulation may reflect mononuclear phagocyte motility within sites of inflammation.

Induction by zinc of specific metallothionein isoforms in human monocytes.

A low-molecular-mass zinc-containing protein was isolated by gel permeation and anion-exchange chromatography of lysates of human monocytes induced with zinc acetate. Characterization by sodium dodecyl sulphate/polyacrylamide gel electrophoresis and amino acid sequencing identified the two major charge-separable fractions and an occasionally occurring third fraction as metallothionein-1, metallothionein-2 and metallothionein-0, respectively. Metallothionein-1 was shown to consist of a mixture of isoforms, confirmed as metallothionein-1e, metallothionein-1g and metallothionein-1l by comparison with cDNA sequences obtained by screening a human monocyte cDNA library. We can find no previous observation in the literature of metallothionein-1g at both the protein and RNA level in a non-tumour cell, and of metallothionein-0 in a non-fetal cell or tissue. Since isoform-specific polymerase-chain-reaction amplification showed the presence of metallothionein-0 mRNA in zinc-induced but not in untreated monocytes, these cells can be used as an in vitro system to investigate the expression of this previously considered fetal isoform.

Antagonistic action of IFN-beta and IFN-gamma on high affinity Fc gamma receptor expression in healthy controls and multiple sclerosis patients.

Monocyte-macrophage activation by IFN-gamma is characterized by a pronounced increase of high affinity Fc receptors for IgG (Fc gamma RI), capable of triggering respiratory burst, phagocytosis, Ab-dependent cytotoxicity, and release of proinflammatory cytokines. In view of the antagonism of IFN-beta on IFN-gamma action, of interest in the chronic inflammatory disorder multiple sclerosis, we examined the possible effect of IFN-beta on IFN-gamma induction of Fc gamma RI gene expression. We found that IFN-beta significantly down-regulated IFN-gamma-induced Fc gamma RI surface expression in peripheral blood monocytes from healthy donors, in a dose- and time-dependent manner. This down-regulation of Fc gamma RI surface levels did not correspond to a decrease in Fc gamma RI mRNA, suggesting a posttranscriptional effect of IFN-beta. Down-regulation of Fc gamma RI surface expression correlated with diminished cellular signaling through Fc gamma RI, since the IFN-gamma-induced increase in Fc gamma receptor-triggered respiratory burst was nearly completely abrogated by simultaneous addition of IFN-beta. Finally, the same antagonism between both IFNs on Fc gamma RI surface expression was observed in peripheral blood monocytes derived from multiple sclerosis patients; inhibition by IFN-beta was even increased (82+/-11%), as compared with healthy controls (67+/-4%). These results may partially help explain the beneficial effect of IFN-beta in multiple sclerosis.