RESUMEN

Vacancies in simple cubic crystals of hard cubes are known to delocalize over one-dimensional chains of several lattice sites. Here, we use computer simulations to examine the structure and dynamics of vacancies in simple cubic crystals formed by hard cubes, right rhombic prisms (slanted cubes), truncated cubes, and particles interacting via a soft isotropic pair potential. We show that these vacancies form a vacancy analog of the crowdion interstitial, generating a strain field which follows a soliton solution of the sine-Gordon equation, and diffusing via a persistent random walk. Surprisingly, we find that the structure of these "voidions" is not significantly affected by changes in density, vacancy concentration, and even particle interaction. We explain this structure quantitatively using a one-dimensional model that includes the free-energy barrier particles have to overcome to slide between lattice sites and the effective pair interaction along this line. We argue that voidions are a robust phenomenon in systems of repulsive particles forming simple cubic crystals.

RESUMEN

We use computer simulations to study the phase behaviour for hard, right rhombic prisms as a function of the angle of their rhombic face (the "slant" angle). More specifically, using a combination of event-driven molecular dynamics simulations, Monte Carlo simulations, and free-energy calculations, we determine and characterize the equilibrium phases formed by these particles for various slant angles and densities. Surprisingly, we find that the equilibrium crystal structure for a large range of slant angles and densities is the simple cubic crystal-despite the fact that the particles do not have cubic symmetry. Moreover, we find that the equilibrium vacancy concentration in this simple cubic phase is extremely high and depends only on the packing fraction and not the particle shape. At higher densities, a rhombic crystal appears as the equilibrium phase. We summarize the phase behaviour of this system by drawing a phase diagram in the slant angle-packing fraction plane.

RESUMEN

Using computer simulations we explore how grain boundaries can be removed from three-dimensional colloidal crystals by doping with a small fraction of active colloids. We show that for sufficient self-propulsion, the system is driven into a crystal-fluid coexistence. In this phase separated regime, the active dopants become mobile and spontaneously gather at the grain boundaries. The resulting surface melting and recrystallization of domains result in the motion of the grain boundaries over time and lead to the formation of a large single crystal. However, when the self-propulsion is too low to cause a phase separation, we observe no significant enhancement of grain growth.

RESUMEN

Using simulations we explore the behaviour of two-dimensional colloidal (poly)crystals doped with active particles. We show that these active dopants can provide an elegant new route to removing grain boundaries in polycrystals. Specifically, we show that active dopants both generate and are attracted to defects, such as vacancies and interstitials, which leads to clustering of dopants at grain boundaries. The active particles both broaden and enhance the mobility of the grain boundaries, causing rapid coarsening of the crystal domains. The remaining defects recrystallize upon turning off the activity of the dopants, resulting in a large-scale single-domain crystal.

RESUMEN

In this paper we study a two-dimensional system of charged colloidal particles using Brownian dynamics simulations. We determine the phase diagram and investigate the dynamics of this system in the density regime where hexatic and solid phases are stable. We find that the dynamics in these phases is heterogeneous by means of the spontaneous formation and diffusion of highly mobile defects. We identify two key mechanisms associated with the areas of high mobility. The first mechanism involves the highly cooperative motion of a closed loop of particles which shift coherently along the loop until each particle has replaced the position of its predecessor in the chain. The second mechanism involves the spontaneous creation of vacancy-interstitial pairs which diffuse within the hexatic and solid phases. We further explore quantitatively the properties of the open-ended and closed rearrangement strings and find that in the crystal phase the string-size distribution can be approximately matched with a simple, random walk description of vacancies and interstitials on a lattice.

RESUMEN

Cancer stem cells (CSCs) are responsible for tumor initiation and progression. Toll-like receptors (TLRs) are highly expressed in cancer cells and associated with poor prognosis. However, a linkage between CSCs and TLRs is unclear, and potential intervention strategies to prevent TLR stimulation-induced CSC formation and underlying mechanisms are lacking. Here, we demonstrate that stimulation of toll-like receptor 3 (TLR3) promotes breast cancer cells toward a CSC phenotype in vitro and in vivo. Importantly, conventional NF-κB signaling pathway is not exclusively responsible for TLR3 activation-enriched CSCs. Intriguingly, simultaneous activation of both ß-catenin and NF-κB signaling pathways, but neither alone, is required for the enhanced CSC phenotypes. We have further identified a small molecule cardamonin that can concurrently inhibit ß-catenin and NF-κB signals. Cardamonin is capable of effectively abolishing TLR3 activation-enhanced CSC phenotypes in vitro and successfully controlling TLR3 stimulation-induced tumor growth in human breast cancer xenografts. These findings may provide a foundation for developing new strategies to prevent the induction of CSCs during cancer therapies.

Asunto(s)

Neoplasias de la Mama/patología , FN-kappa B/metabolismo , Células Madre Neoplásicas/metabolismo , Receptor Toll-Like 3/metabolismo , beta Catenina/metabolismo , Animales , Línea Celular Tumoral , Chalconas/farmacología , Modelos Animales de Enfermedad , Femenino , Humanos , Ratones Desnudos , FN-kappa B/genética , Trasplante de Neoplasias , Fenotipo , Transducción de Señal , Receptor Toll-Like 3/genética , beta Catenina/genética

RESUMEN

In this study, we investigated the role and expression of T helper type 17 (Th17) cells and Th17 cytokines in human tuberculosis. We show that the basal proportion of interferon (IFN)-γ-, interleukin (IL)-17- and IL-22-expressing CD4(+) T cells and IL-22-expressing granulocytes in peripheral blood were significantly lower in latently infected healthy individuals and active tuberculosis patients compared to healthy controls. In contrast, CD4(+) T cells expressing IL-17, IL-22 and IFN-γ were increased significantly following mycobacterial antigens stimulation in both latent and actively infected patients. Interestingly, proinflammatory IFN-γ and tumour necrosis factor (TNF)-α were increased following antigen stimulation in latent infection. Similarly, IL-1ß, IL-4, IL-8, IL-22 and TNF-α were increased in the serum of latently infected individuals, whereas IL-6 and TNF-α were increased significantly in actively infected patients. Overall, we observed differential induction of IL-17-, IL-22- and IFN-γ-expressing CD4(+) T cells, IL-22-expressing granulocytes and proinflammatory cytokines in circulation and following antigenic stimulation in latent and active tuberculosis.

Asunto(s)

Linfocitos T CD4-Positivos/metabolismo , Citocinas/sangre , Granulocitos/metabolismo , Interferón gamma/sangre , Interleucinas/sangre , Tuberculosis/sangre , Adulto , Etnicidad , Femenino , Humanos , Inflamación/sangre , Tuberculosis Latente/sangre , Tuberculosis Latente/etnología , Tuberculosis Latente/inmunología , Masculino , Persona de Mediana Edad , ARN Mensajero/sangre , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Th17/metabolismo , Tuberculosis/etnología , Tuberculosis/inmunología , Factor de Necrosis Tumoral alfa/sangre , Adulto Joven , Interleucina-22

RESUMEN

We determine the phase diagram of a binary mixture of small and large hard spheres with a size ratio of 0.3 using free-energy calculations in Monte Carlo simulations. We find a stable binary fluid phase, a pure face-centered-cubic (fcc) crystal phase of the small spheres, and binary crystal structures with LS and LS(6) stoichiometries. Surprisingly, we demonstrate theoretically and experimentally the stability of a novel interstitial solid solution in binary hard-sphere mixtures, which is constructed by filling the octahedral holes of an fcc crystal of large spheres with small spheres. We find that the fraction of octahedral holes filled with a small sphere can be completely tuned from 0 to 1. Additionally, we study the hopping of the small spheres between neighboring octahedral holes, and interestingly, we find that the diffusion increases upon increasing the density of small spheres.

RESUMEN

In this paper we examine the phase behavior of the Weeks-Chandler-Andersen (WCA) potential with ßε = 40. Crystal nucleation in this model system was recently studied by Kawasaki and Tanaka [Proc. Natl. Acad. Sci. U.S.A. 107, 14036 (2010)], who argued that the computed nucleation rates agree well with experiment, a finding that contradicted earlier simulation results. Here we report an extensive numerical study of crystallization in the WCA model, using three totally different techniques (Brownian dynamics, umbrella sampling, and forward flux sampling). We find that all simulations yield essentially the same nucleation rates. However, these rates differ significantly from the values reported by Kawasaki and Tanaka and hence we argue that the huge discrepancy in nucleation rates between simulation and experiment persists. When we map the WCA model onto a hard-sphere system, we find good agreement between the present simulation results and those that had been obtained for hard spheres [L. Filion, M. Hermes, R. Ni, and M. Dijkstra, J. Chem. Phys. 133, 244115 (2010); S. Auer and D. Frenkel, Nature 409, 1020 (2001)].

RESUMEN

Over the last number of years several simulation methods have been introduced to study rare events such as nucleation. In this paper we examine the crystal nucleation rate of hard spheres using three such numerical techniques: molecular dynamics, forward flux sampling, and a Bennett-Chandler-type theory where the nucleation barrier is determined using umbrella sampling simulations. The resulting nucleation rates are compared with the experimental rates of Harland and van Megen [Phys. Rev. E 55, 3054 (1997)], Sinn et al. [Prog. Colloid Polym. Sci. 118, 266 (2001)], Schätzel and Ackerson [Phys. Rev. E 48, 3766 (1993)], and the predicted rates for monodisperse and 5% polydisperse hard spheres of Auer and Frenkel [Nature 409, 1020 (2001)]. When the rates are examined in units of the long-time diffusion coefficient, we find agreement between all the theoretically predicted nucleation rates, however, the experimental results display a markedly different behavior for low supersaturation. Additionally, we examined the precritical nuclei arising in the molecular dynamics, forward flux sampling, and umbrella sampling simulations. The structure of the nuclei appears independent of the simulation method, and in all cases, the nuclei contains on average significantly more face-centered-cubic ordered particles than hexagonal-close-packed ordered particles.

RESUMEN

Binary colloidal crystals offer great potential for tuning material properties for applications in, for example, photonics, semiconductors and spintronics, because they allow the positioning of particles with quite different characteristics on one lattice. For micrometer-sized colloids, it is believed that gravity and slow crystallization rates hinder the formation of high-quality binary crystals. Here, we present methods for growing binary colloidal crystals with a NaCl structure from relatively heavy, hard-sphere-like, micrometer-sized silica particles by exploring the following external fields: electric, gravitational, and dielectrophoretic fields and a structured surface (colloidal epitaxy). Our simulations show that the free-energy difference between the NaCl and NiAs structures, which differ in their stacking of the hexagonal planes of the larger spheres, is very small (approximately 0.002 k(B)T). However, we demonstrate that the fcc stacking of the large spheres, which is crucial for obtaining the pure NaCl structure, can be favored by using a combination of the above-mentioned external fields. In this way, we have successfully fabricated large, 3D, oriented single crystals having a NaCl structure without stacking disorder.

Asunto(s)

Coloides/química , Cloruro de Sodio/química , Cristalización , Campos Electromagnéticos , Electroforesis , Gravitación , Microscopía Confocal , Modelos Moleculares , Estructura Molecular , Tamaño de la Partícula , Dióxido de Silicio/química , Estrés Mecánico

RESUMEN

We study by computer simulations the stability of various crystal structures in a binary mixture of large and small spheres interacting either with a hard sphere or a screened-Coulomb potential. In the case of hard-core systems, we consider structures that have atomic prototypes CrB, gammaCuTi, alphaIrV, HgBr2, AuTe2, Ag2Se and the Laves phases (MgCu2, MgNi2, and MgZn2) as well as a structure with space group symmetry 74. By utilizing Monte Carlo simulations to calculate Gibbs free energies, we determine composition versus pressure and constant volume phase diagrams for diameter ratios of q=0.74, 0.76, 0.8, 0.82, 0.84, and 0.85 for the small and large spheres. For diameter ratios 0.76 < or = q < or = 0.84, we find the Laves phases to be stable with respect to the other crystal structures that we considered and the fluid mixture. By extrapolating to the thermodynamic limit, we show that the MgZn2 structure is the most stable one of the Laves structures. We also calculate phase diagrams for equally and oppositely charged spheres for size ratio of 0.73 taking into consideration the Laves phases and CsCl. In the case of equally charged spheres, we find a pocket of stable Laves phases, while in the case of oppositely charged spheres, Laves phases are found to be metastable with respect to the CsCl and fluid phases.

RESUMEN

Flow cytometry has evolved from single- and two-color analysis to the current use of 11-16 colors. The relatively bright excitation spectra of most fluorochromes have made color compensation a challenge especially when performed manually. We describe how by choosing filters with narrower bandwidths results in the color compensation values between FITC, PE, PE-TxR (ECD), PE-Cy5, and PE-Cy7 that range from 0 % to 50% depending on the combination of fluorochromes. Peripheral blood mononuclear cells were stained with alpha-CD4-FITC, alpha-CD27-PE, alpha-CD62L-ECD, alpha-CD45RA-PE-Cy5 and alpha-CD3-PE-Cy7. The samples were acquired on a MO Flo. The initial (first) and second filter sets for our experiments consisted of 530/30 or 519/20 for FITC, 580/30 or 575/20for PE, 630/30 or 630/22 for PE-TxR (ECD), 670/30 or 675/20 for PE-Cy5 and 740LP or 780/40 for PE-Cy7. Nonstained cells were used to adjust the threshold values of detection for each photo multiplier tube (PMT) for each filter set. The mean fluorescent intensity (MFI) of each fluorochrome was not reduced to any great extent by either filter set. However, the compensation value between PE and PE-TxR (ECD) with the first filter selection ranged from 84% to 89% and with the second set of filters it was 25-36%. In addition, the compensation between PE-TxR (ECD) and PE-Cy5 were reduced to 30.2% from 44.2% with the second filter set. The reduction of filter bandwidths that results in minimizing spectral overlaps without lost of signal provides a method by which discrimination of signals between PE containing fluorochromes can be achieved.

Asunto(s)

Citometría de Flujo/métodos , Recuento de Leucocitos/métodos , Citometría de Flujo/instrumentación , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Rayos Láser , Recuento de Leucocitos/instrumentación , Espectrometría de Fluorescencia/métodos

RESUMEN

MS is an inflammatory, presumably autoimmune, disease mediated by the activation of T cells, B cells and monocytes (MO). Inflammation is thought to occur early during the relapsing-remitting phase of MS (RRMS), whereas in the later phases of MS such as secondary progressive MS (SPMS), inflammation tends to diminish. Our objective was to compare the types and amounts of proinflammatory and regulatory cytokines produced by MO from relapsing-remitting patients with or without treatment with IFN-beta (RRMS+ therapy, RRMS- therapy), respectively, from secondary progressive patients (SPMS) and from healthy controls (HC). MO were isolated by a density-gradient technique and three different techniques (RNase protection assay, ELISA and intracellular cytokine staining) were used to assess cytokine levels. An increase in IL6, IL12 and TNF-alpha was observed by all three methods for RRMS- therapy and for SPMS patients compared to HC and RRMS+ therapy patients. We conclude that proinflammatory and regulatory monokines can be derived from MO of MS patients and that these levels are modulated by IFN-beta therapy. Although it is believed that inflammation tends to diminish in SPMS patients, our data show that inflammatory cytokines continue to be released at high levels, suggesting that IFN-beta or IL10 treatment may be beneficial for this group.

Asunto(s)

Citocinas/biosíntesis , Monocitos/inmunología , Esclerosis Múltiple/inmunología , Adolescente , Adulto , Anciano , Células Cultivadas , Citocinas/genética , Progresión de la Enfermedad , Femenino , Expresión Génica , Humanos , Interferón beta/uso terapéutico , Interleucina-10/uso terapéutico , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/terapia , Esclerosis Múltiple Crónica Progresiva/inmunología , Esclerosis Múltiple Crónica Progresiva/terapia , Esclerosis Múltiple Recurrente-Remitente/inmunología , Esclerosis Múltiple Recurrente-Remitente/terapia , ARN Mensajero/genética , Proteínas Recombinantes/uso terapéutico

RESUMEN

The natural habitat of Legionella is the water environment. Little is known about their presence in groundwater in spite of the fact that many millions around the globe regularly rely on groundwaters. This pilot study was aimed at evaluating the occurrence of Legionella in groundwater samples (water and biofilms) collected from various sites. Water and biofilm samples from selected groundwater sources were examined for Legionella using culture media (selective and non-selective) and a semi-nested PCR assay. Innovative approaches such as immunomagnetic separation (IMS) in combination with cultivation and flow cytometry were also evaluated. The findings available thus far show that (a) Legionella could be readily recovered from groundwater samples by cultivation even though their numbers showed considerable variations, (b) surprisingly, the PCR methodology was not yet as sensitive as cultivation and (c) flow cytometry was not directly applicable on natural samples because of debris and the high number of heterotrophic associated microflora from which some members were likely to cross-react with the monoclonal antibody used for separation procedures (IMS).

Asunto(s)

Legionella , Microbiología del Suelo , Abastecimiento de Agua , Biopelículas , ADN Bacteriano/análisis , Monitoreo del Ambiente , Citometría de Flujo , Humanos , Reacción en Cadena de la Polimerasa , Dinámica Poblacional , Salud Pública , Sensibilidad y Especificidad

RESUMEN

ALX40-4C is a small peptide inhibitor of the chemokine receptor CXCR4 that can inhibit X4 strains of HIV-1. Prior to the discovery of chemokine receptors as the HIV coreceptors, ALX40-4C was used in phase I/II clinical trials to evaluate its therapeutic potential against HIV-1, making ALX40-4C the first anticoreceptor inhibitor to be tested in humans against HIV-1. Patients in the highest dose groups achieved ALX40-4C levels above the effective concentration of the drug for nearly the entire 1-month treatment period. ALX40-4C was well tolerated by 39 of 40 asymptomatic HIV-infected patients, despite the critical role of CXCR4 in normal development and hematopoiesis. No significant or consistent reductions in viral load were observed, but only 12 of the enrolled patients harbored virus types that used CXCR4. We also found that ALX40-4C interacts with the second extracellular loop of CXCR4 and inhibits infection exclusively by blocking direct virus-CXCR4 interactions.

Asunto(s)

Fármacos Anti-VIH/uso terapéutico , Infecciones por VIH/tratamiento farmacológico , VIH-1/efectos de los fármacos , Oligopéptidos/uso terapéutico , Receptores CXCR4/antagonistas & inhibidores , Adulto , Fármacos Anti-VIH/administración & dosificación , Fármacos Anti-VIH/metabolismo , Fármacos Anti-VIH/farmacocinética , Linfocitos T CD4-Positivos/efectos de los fármacos , Linfocitos T CD8-positivos/efectos de los fármacos , Línea Celular , Seguridad de Productos para el Consumidor , Femenino , Infecciones por VIH/sangre , Humanos , Masculino , Persona de Mediana Edad , Oligopéptidos/administración & dosificación , Oligopéptidos/metabolismo , Oligopéptidos/farmacocinética , Receptores CXCR4/genética , Receptores CXCR4/metabolismo , Receptores CXCR4/fisiología

RESUMEN

The cytokine IL-12 manifests its biological activity via interaction with a heterodimeric receptor (IL-12R) present on activated T and NK cells. The cDNAs for two IL-12R subunits have been cloned from human and mouse and designated IL-12Rbeta1 and IL-12Rbeta2. The expression of IL-12Rbeta2 on T cells is influenced by cytokines, particularly IL-4, IL-12, and IFN-gamma; however, little is known regarding regulation of IL-12R expression on NK cells. In this study we show that murine NK cells differentiate into IL-12Rbeta2(low) and IL-12Rbeta2(high) subsets after in vitro stimulation with IL-2 in the absence of exogenous polarizing cytokines. Subset development occurs gradually as NK cells expand in vitro and is generally complete by 8-12 days of culture. Once established, IL-12Rbeta2(low) and IL-12Rbeta2(high) subsets are highly stable in vitro and can be maintained for at least 20 days after FACS sorting. Formation of these NK subsets appears to be strain independent. Flow cytometric analyses demonstrate that both subsets express a number of NK-associated markers, including NK1.1, DX-5, Ly-49A, and Ly-49C, but that the Ly-49G2 class I inhibitory receptor is expressed predominantly on the IL-12Rbeta2(high) population. Both IL-12Rbeta2(low) and IL-12Rbeta2(high) NK cells respond to exogenous IL-12 by rapid production of high levels of IFN-gamma and increased lytic activity against NK-sensitive YAC-1 target cells. Analyses of cytokine gene expression by RNase protection assay indicated that similar to the recently described human NK1 subset, both IL-12Rbeta2(high) and IL-12Rbeta2(low) murine NK subsets expressed high levels of IFN-gamma, whereas neither subset expressed mRNA for the NK2-associated cytokines IL-5 and IL-13.

Asunto(s)

Antígenos Ly , Interleucina-12/metabolismo , Células Asesinas Naturales/citología , Células Asesinas Naturales/metabolismo , Subgrupos Linfocitarios/citología , Subgrupos Linfocitarios/metabolismo , Receptores de Interleucina/biosíntesis , Animales , Especificidad de Anticuerpos , Diferenciación Celular/inmunología , Citocinas/biosíntesis , Citocinas/genética , Citotoxicidad Inmunológica , Dimerización , Femenino , Citometría de Flujo , Sueros Inmunes/biosíntesis , Inmunofenotipificación , Interferón gamma/biosíntesis , Células Asesinas Naturales/inmunología , Lectinas Tipo C , Activación de Linfocitos , Subgrupos Linfocitarios/inmunología , Glicoproteínas de Membrana/biosíntesis , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , ARN Mensajero/biosíntesis , Receptores de Interleucina/análisis , Receptores de Interleucina/inmunología , Receptores de Interleucina-12 , Receptores Similares a Lectina de Células NK

RESUMEN

The down regulation of CD4 by cultured monocytes has been observed by our group and by other investigators. Flow cytometric experiments were done to examine which factors might influence this phenomenon. The addition of lipopolysaccharide, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor, or interleukin-10 to monocyte cultures failed to inhibit the decrease in monocyte CD4 expression routinely observed following overnight culture. The down regulation was an adherence-independent phenomenon and was not influenced by the type of anticoagulant into which the peripheral blood was collected or by the presence or absence of lymphocytes within the cultures. The avoidance of the use of Ficoll-Paque to isolate peripheral blood mononuclear cells did not prevent monocyte CD4 down regulation. Finally, by tagging monocyte CD4 with an anti-CD4 phycoerythrin-conjugated monoclonal antibody prior to culture, we were able to determine that the down regulation observed was the result of the internalization of the molecule. At this time, we conclude that the observed down regulation of monocyte CD4 is probably due to the differentiation of blood monocytes into tissue culture-derived macrophages rather than to some artifact of the isolation procedure.

Asunto(s)

Antígenos CD4/biosíntesis , Regulación hacia Abajo , Monocitos/inmunología , Anticoagulantes , Adhesión Celular , Células Cultivadas , Ácido Cítrico , Ácido Edético , Glucosa/análogos & derivados , Factor Estimulante de Colonias de Granulocitos y Macrófagos/inmunología , Factor Estimulante de Colonias de Granulocitos y Macrófagos/farmacología , Heparina , Humanos , Interleucina-10/inmunología , Interleucina-10/farmacología , Cinética , Leucocitos Mononucleares/citología , Leucocitos Mononucleares/efectos de los fármacos , Leucocitos Mononucleares/inmunología , Lipopolisacáridos/inmunología , Lipopolisacáridos/farmacología , Factor Estimulante de Colonias de Macrófagos/inmunología , Factor Estimulante de Colonias de Macrófagos/farmacología , Monocitos/citología , Monocitos/efectos de los fármacos , Factores de Tiempo

RESUMEN

T helper (Th) responses are mediated in part by immunoregulatory cytokines and the signals delivered by the costimulatory CD28-B7 pathway. In this study, we have investigated the relationship between the regulation of B7 isoform expression on antigen-presenting cells from HIV+ individuals and the production of Th cytokines. The level of expression of both B7.1 and B7.2 isoforms as measured by mean channel fluorescence was significantly decreased on freshly isolated monocytes from HIV+ individuals compared with HIV- controls. However, the levels of expression of B7.1 and B7.2 on both B cells and monocytes increased significantly following culture in HIV+ individuals compared with HIV- controls. B7 expression is subject to regulation by immunoregulatory cytokines. Therefore, we analysed the regulation of B7 expression by cytokines, namely IL-10 and tumour necrosis factor-alpha (TNF-alpha), the production of which is enhanced in HIV infection and have similar inhibitory effects on B7 expression. Two groups of HIV+ individuals were distinguished on the basis of the inhibitory effect of IL-10 and TNF-alpha on monocyte B7.2 expression. IL-10 inhibited B7.2 expression on monocytes from some HIV+ individuals (termed responders) like the HIV- controls. However, in a subset of HIV+ individuals (non-responders) this inhibitory effect was lost. Loss of inhibition of B7.2 expression by IL-10 was associated with significantly reduced IL-2 production by phytohaemagglutinin (PHA)- stimulated peripheral blood mononuclear cells (PBMC). These observations showing an association of B7 dysregulation on monocytes and B cells with altered production of IL-2 may have implications in HIV immunopathogenesis.

Asunto(s)

Antígenos CD/biosíntesis , Regulación de la Expresión Génica , Infecciones por VIH/inmunología , Interleucina-2/biosíntesis , Leucocitos Mononucleares/metabolismo , Glicoproteínas de Membrana/biosíntesis , Adulto , Antígenos CD/genética , Linfocitos B/inmunología , Antígeno B7-2 , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Interleucina-10/farmacología , Interleucina-2/genética , Leucocitos Mononucleares/efectos de los fármacos , Cooperación Linfocítica/efectos de los fármacos , Glicoproteínas de Membrana/genética , Células TH1/inmunología , Células TH1/metabolismo , Células Th2/inmunología , Células Th2/metabolismo , Factor de Necrosis Tumoral alfa/farmacología

RESUMEN

Immune unresponsiveness in HIV-1 infection can result from impaired signals delivered by the costimulatory CD28-B7 pathway and the altered production of immunoregulatory cytokines, in particular IL-10, whose production is altered in HIV-1 infection. In this study we investigate IL-10 regulation in T cells and monocytes from HIV+ individuals, and its association with CD28-mediated T cell proliferation. IL-10 production as analysed in T cell- and monocyte-depleted peripheral blood mononuclear cells (PBMC), and by intracellular staining at the single-cell level, reveals a defect in IL-10 production by CD4+ and CD8+ T cells, whereas monocytes constitute the major IL-10-producing cell type. To investigate the impact of IL-10 on immune responsiveness, CD28-mediated proliferative responses in HIV+ individuals were correlated with PHA-induced IL-10 production. CD4+ T cells expressed CD28, yet exhibited markedly reduced CD28-mediated cell proliferation. This CD28-mediated CD4+ T cell proliferation was found to be inversely associated with the levels of PHA-induced IL-10 production and could be restored, at least in part, by anti-IL-10 antibodies. These results suggest that IL-10 production is differentially regulated in T cells and monocytes of HIV+ individuals, and that IL-10 may have a role in inducing immune unresponsiveness by modulating the CD28-B7 pathway.

Asunto(s)

Antígenos CD28/inmunología , Infecciones por VIH/inmunología , Interleucina-10/biosíntesis , Monocitos/metabolismo , Linfocitos T/metabolismo , Adulto , División Celular , Células Cultivadas , Regulación hacia Abajo , Humanos , Leucocitos Mononucleares/efectos de los fármacos , Leucocitos Mononucleares/metabolismo , Mitógenos/farmacología , Fitohemaglutininas/farmacología