Pre-validation of SENS-IS assay for in vitro skin sensitization of medical devices

According to ISO 10993-1:2018, the skin sensitization potential of all medical devices must be evaluated, and for this endpoint ISO 10993-10:2010 recommends the use of in vivo assays. The goal of the present study was to determine if the in vitro SENS-IS assay could be a suitable alternative to the current in vivo assays. The SENS-IS assay uses the Episkin Large and SkinEthic RHE reconstructed human epidermis models to evaluate marker genes. In our study, the SENS-IS assay correctly identified 13 sensitizers spiked in a non-polar solvent. In a subsequent analysis six medical device silicone samples previously impregnated with sensitizers were extracted with polar and non-polar solvents. The SENS-IS assay correctly identified five of these extracts, while a sixth extract, which contained the weak sensitizer phenyl benzoate, was classified as negative. However, when this extract was concentrated, or a longer exposure time was used, the assay was able to detect phenyl benzoate. The SENS-IS assay was transferred to a naïve laboratory which correctly identified sensitizers in six blinded silicone samples, including the one containing phenyl benzoate. In light of these results, we conclude that the SENS-IS assay is able to correctly identify the presence of sensitizers in medical devices extracts.

Genes specifically modulated in sensitized skins allow the detection of sensitizers in a reconstructed human skin model. Development of the SENS-IS assay

Analysis of genes modulated during the sensitization process either on mice (LLNA) or human (blisters) combined with data mining has allowed the definition of a comprehensive panel of sensitization biomarkers. This set of genes includes already identified markers such as the ARE family and others not yet associated with the sensitization process (the so-called SENS-IS gene subset). The expression of this set of genes has been measured on reconstituted human epidermis models (Episkin) exposed to various sensitizers and non-sensitizers. Fine analysis of their expression pattern indicates that it is the number of modulated genes rather than the intensity of up-regulation that correlates best with the sensitization potential of a chemical. Moreover, sensitizers that are weak inductors of ARE genes tend to be relevant modulators of the SENS-IS subset. By combining the expression data obtained with both gene subsets, it is now possible to identify a wide variety of sensitizers on a test system (in vitro reconstructed human epidermis) that is very similar to the in vivo situation and compatible with a large variety of test substance characteristics.

Saccharomyces boulardii inhibits inflammatory bowel disease by trapping T cells in mesenteric lymph nodes

BACKGROUND & AIMS

Saccharomyces boulardii is a nonpathogenic yeast used for treatment of diarrhea. We used a mice model of inflammatory bowel disease (IBD) to analyze the effects of S boulardii on inflammation.

METHODS

Lymphocyte-transferred SCID mice, displaying IBD, were fed daily with S boulardii. Weight loss and inflammatory status of the colon were monitored. Nuclear factor-kappaB activity was assessed in the colon. The CD4(+) T-cell production of interferon (IFN) gamma was evaluated by enzyme-linked immunosorbent assay, and a comprehensive reverse-transcription polymerase chain reaction (RT-PCR) analysis for both colon and mesenteric lymph nodes was performed. Finally, we analyzed cell migration mechanisms in vitro and in vivo.

RESULTS

S boulardii treatment inhibits IBD. S boulardii induces an accumulation of IFN-gamma-producing T-helper 1 cells within the mesenteric lymph nodes correlated with a diminution of CD4(+) T-cell number and IFN-gamma production by CD4+ T cells within the colon. The influence of S boulardii treatment on cell accumulation in mesenteric lymph nodes was also observed in normal BALB/c mice and involves modifications of lymph node endothelial cell adhesiveness by a yeast secretion product.

CONCLUSIONS

S boulardii has a unique action on inflammation by a specific alteration of the migratory behavior of T cells, which accumulate in mesenteric lymph nodes. Therefore, S boulardii treatment limits the infiltration of T-helper 1 cells in the inflammed colon and the amplification of inflammation induced by proinflammatory cytokines production. These results suggest that S boulardii administration may have a beneficial effect in the treatment of IBD.

LiveStaphylococcus aureusand bacterial soluble factors induce different transcriptional responses in human airway cells

To characterize the response of respiratory epithelium to infection by Staphylococcus aureus ( S. aureus), human airway cells were incubated for 1 to 24 h with a supernatant of a S. aureus culture (bacterial supernatant), then profiled with a pangenomic DNA microarray. Because an upregulation of many genes was noticed around 3 h, three independent approaches were then used to characterize the host response to a 3-h contact either with bacterial supernatant or with live bacteria: 1) a DNA microarray containing 4,200 sequence-verified probes, 2) a semiquantitative RT-PCR with a set of 537 pairs of validated primers, or 3) ELISA assay of IL-8, IL-6, TNFα, and PGE2. Among others, Fos, Jun, and EGR-1 were upregulated by the bacterial supernatant and by live bacteria. Increased expression of bhlhb2 and Mig-6, promoter regions which harbor HIF responding elements, was explained by an increased expression of the HIF-1α protein. Activation of the inducible form of cyclooxygenase, COX-2, and of the interleukins IL-1, IL-6, and IL-8, as well as of the NF-κB pathway, was observed preferentially in cells in contact with bacterial supernatant. Early infection was characterized by an upregulation of anti-apoptotic genes and a downregulation of pro-apoptotic genes. This correlated with a necrotic, rather than apoptotic cell death. Overall, this first global description of an airway epithelial infection by S. aureus demonstrates a larger global response to bacterial supernatant (in term of altered genes and variation factors) than to exponentially growing live bacteria.

Role of dendritic cells in the generation of regulatory T cells

The induction of antigen-specific T-cell tolerance in the thymus and its maintenance in the periphery is crucial for the prevention of autoimmunity. It was recently proposed that cells of the dendritic family not only control immunity but also maintain tolerance to self-antigens, two complementary functions that would ensure the integrity of the organism in an environment full of pathogens. The tolerogenic function of dendritic cells has been shown to be dependent on certain maturation stages and subsets of different ontogenies, and can be influenced by immunomodulatory agents. Here we discuss the current knowledge of these tolerogenic dendritic cells and how might the understanding of the function and characterization of tolerance-inducing dendritic cells be relevant to therapeutic applications.

Human Immunodeficiency Virus Protease Inhibitors Accumulate into Cultured Human Adipocytes and Alter Expression of Adipocytokines

Lipodystrophic syndrome is a major side effect of highly active antiviral therapy. Fat tissue redistribution is associated with changes in adipocyte gene expression and in circulating levels of adipocytokines involved in the development of insulin resistance. However, the evidence that HIV drugs accumulate into human adipocytes and have a direct effect on the expression of adipocyte-specific genes is still lacking. To address these questions, we used adipocytes derived from adult stem (hMADS) cells isolated from human adipose tissue. We showed by ELISA that two inhibitors of the HIV protease, lopinavir and ritonavir, accumulated at similar levels during the development of hMADS cells in adipocytes, whereas a non-nucleoside reverse transcriptase inhibitor, the nevirapine, accumulated at lower levels. Two fluorescent protease inhibitors then have been generated to investigate their subcellular localization. The data showed that HIV drugs accumulated into adipocytes and displayed various effects on hMADS cell-derived adipocytes. Indinavir, amprenavir, and nevirapine did not alter differentiation of precursor cells. In contrast, lopinavir, saquinavir, and ritonavir inhibited the development of preadipocytes into adipocytes. In adipocytes, amprenavir increased leptin expression and ritonavir was able to up-regulate tumor necrosis factor-alpha, interleukin 6, and leptin expression and down-regulate the expression of peroxisome proliferator-activated receptor gamma and adiponectin. Intracellular accumulation and localization of HIV drugs into human adipocytes strongly suggest that adipose tissues store these drugs. Because ritonavir can alter the expression of insulin resistance-related cytokines in human adipocytes in a way parallel to the situation observed in vivo upon treatment of HIV-infected patients, we propose that protease inhibitors participate in insulin resistance through a direct effect on adipocytes.

A comparative study between T regulatory type 1 and CD4+CD25+ T cells in the control of inflammation

There is now compelling evidence that CD4(+)CD25(+) T cells play a major role in the maintenance of tolerance. Besides CD4(+)CD25(+) T cells, different populations of regulatory CD4(+) T cells secreting high amounts of IL-10 (T regulatory type 1 (Tr1)) or TGF-beta (Th3) have also been described in in vivo models. In the lymphocyte transfer model of inflammatory bowel disease, we show here that the control of inflammation during the first weeks is not due to a complete inhibition of differentiation of aggressive proinflammatory T cells, but is the result of a balance between proinflammatory and Tr cells. We also show that in the first weeks continuous IL-10 secretion was required to actively control inflammation. Indeed, treatment with anti-IL-10R Abs 3 wk after the start of the experiment completely reversed the protective effect of Tr cells. IL-10 secretion and control of inflammation could be provided by late injection of Tr1 cells that efficiently cure ongoing inflammatory responses in two different models of inflammation. In contrast, inflammation was not controlled when high numbers of CD4(+)CD45RB(low) or CD4(+)CD25(+) T cells were injected as early as 1 wk after the start of the experiment. These results confirm in vitro studies showing that CD4(+)CD45RB(low) do not contain high IL-10-producing cells and suggest that CD4(+)CD45RB(low) Tr cells maintain tolerance in vivo, in part indirectly, through the differentiation of IL-10-secreting Tr1 cells.

Specialization in tolerance: innate CD(4+)CD(25+) versus acquired TR1 and TH3 regulatory T cells

The regulation of immune responses to self-antigens is a complex process that involves maintaining self-tolerance while retaining the capacity to mount robust immune responses against invading microorganisms. Over the past few years, many new insights into this process have been gained, leading to the reemergence of the idea that regulatory T cells (Treg) are key players in immune regulation. These insights have raised fundamental questions concerning the definition of a Treg and what exactly constitutes T-cell-mediated suppression, identification of the signals and the cellular environment that promote the development and differentiation of these cells, and which signals maintain the homeostasis of the immune system. Thus far, the different models where Treg have been characterized cannot fully account for CD(4+)CD(25+) T cells. In this article, the authors propose the coexistence of two specialized types of CD(4+) Treg-innate and acquired-that differ in terms of their development, specificity, mechanisms, and sites of action.

Mature human thymocytes migrate on laminin-5 with activation of metalloproteinase-14 and cleavage of CD44

We have previously shown that laminin-5 is expressed in the human thymic medulla, in which mature thymocytes are located. We now report that laminin-5 promotes migration of mature medullary thymocytes, whereas it has no effect on cortical immature thymocytes. Migration was inhibited by blocking mAbs directed against laminin-5 integrin receptors and by inhibitors of metalloproteinases. Interactions of thymocytes with laminin-5 induced a strong up-regulation of active metalloproteinase-14. However, we found that thymocytes did not cleave the laminin-5 gamma(2) chain, suggesting that they do not use the same pathway as epithelial cells to migrate on laminin-5. Interactions of thymocytes with laminin-5 also induced the release of a soluble fragment of CD44 cell surface molecule. Moreover, CD44-rich supernatants induced thymocyte migration in contrast with supernatants depleted in CD44 by immunoadsorption. CD44 cleavage was recently reported to be due to metalloproteinase-14 activation and led to increased migration in cancer cells. Thus, in this study, we show that laminin-5 promotes human mature thymocyte migration in vitro via a multimolecular mechanism involving laminin-5 integrin receptors, metalloproteinase-14 and CD44. These data suggest that, in vivo, laminin-5 may function in the migration of mature thymocytes within the medulla and be part of the thymic emigration process.

Specific abrogation of transforming growth factor-beta signaling in T cells alters atherosclerotic lesion size and composition in mice

A large body of evidence supports a role for proinflammatory mediators in atherosclerotic disease progression and instability. However, only few endogenous mechanisms have been suggested that could alter disease progression. One such mechanism is thought to be mediated by transforming growth factor beta (TGF-beta). Transgenic mice that express a dominant-negative TGF-beta receptor type II under a T-cell-specific promoter were generated. Bone marrow transplantation from transgenic mice into irradiated low density lipoprotein receptor knock-out (LDLr KO) mice, subsequently fed an atherogenic diet, resulted in T-cell-specific blockade of TGF-beta signaling in the recipient mice and increased differentiation of T cells toward both T helper 1 (Th1) and Th2 phenotypes. These mice showed a significant decrease in atherosclerotic lesion size in the aortic sinus compared with mice receiving transplants with the wild-type bone marrow. Atherosclerotic plaques of mice receiving transplants with the transgenic bone marrow showed increased T-cell infiltration and expression of major histocompatability complex (MHC) class II, along with a decrease in smooth muscle cell and collagen content, a plaque phenotype that is potentially vulnerable to rupture. These results identify for the first time an important role for specific and selective T-cell-TGF-beta signaling in atherosclerosis.

Induction of a regulatory T cell type 1 response reduces the development of atherosclerosis in apolipoprotein E-knockout mice

BACKGROUND

T helper type 1 (Th1) response plays a permissive role in atherosclerosis. We hypothesized that adoptive transfer of a novel subtype of T lymphocytes called regulatory T cells type 1 (Tr1) would inhibit Th1 responses by inducing a bystander immune suppression and therefore limit the development of atherosclerosis.

METHODS AND RESULTS

Clones of ovalbumin (OVA)-specific Tr1 cells expanded in vitro were administered intraperitoneally (106 cells per mouse) with their cognate antigen (50 microg of OVA subcutaneously in complete Freund's adjuvant [CFA]) to female apolipoprotein E-knockout mice. A group of mice received only (OVA/CFA) immunization without Tr1 cells. Two other control groups received no immunization and were injected with either Tr1 cells or saline. After 9 weeks of treatment, mice injected with (OVA/CFA)+OVA-specific Tr1 cells showed a significant decrease in Th1 responses, as revealed by a decrease in OVA-specific IgG2a serum levels (P<0.0001), a decrease in the production of interferon-gamma (P<0.001), and an increase in interleukin-10 production (P<0.001) by cultured spleen and lymph T cells compared with controls. In addition, cytokine production by concanavalin A-stimulated spleen cells showed a clear switch to a regulatory immune response in mice treated with (OVA/CFA)+Tr1. This was associated with a significant reduction in atherosclerotic lesion size in both the thoracic aorta and aortic sinus of mice treated with (OVA/CFA)+Tr1 compared with controls (P=0.002 to P<0.0001). Plaques of mice injected with (OVA/CFA)+Tr1 showed significantly lower accumulation of macrophages and T cells than plaques of control mice.

CONCLUSIONS

Tr1-type regulatory immune response reduces the development of experimental atherosclerosis.

Involvement of a CD47-dependent pathway in platelet adhesion on inflamed vascular endothelium under flow

Resting platelet adhesion to inflammatory vascular endothelium is thought to play a causal role in secondary thrombus formation or microcirculatory disturbance after vessel occlusion. However, though adhesion receptors involved in platelet-matrix interactions have been extensively studied, the molecular mechanisms involved in platelet-endothelium interactions are incompletely characterized and have been mainly studied under static conditions. Using human platelets or platelets from wild-type and CD47-/- mice in whole blood, we demonstrated that at low shear rate, CD47 expressed on human and mouse platelets significantly contributes to platelet adhesion on tumor necrosis factor-alpha (TNF-alpha)-stimulated vascular endothelial cells. Using the CD47 agonist peptide 4N1K and blocking monoclonal antibodies (mAbs), we showed that CD47 binds the cell-binding domain (CBD) of endothelial thrombospondin-1 (TSP-1), inducing activation of the platelet alphaIIbbeta3 integrin that in turn becomes able to link the endothelial receptors intercellular adhesion molecule 1 (ICAM-1) and alphavbeta3. Platelet CD36 and GPIbalpha are also involved because platelet incubation with blocking mAbs directed against each of these 2 receptors significantly decreased platelet arrest. Given that anti-CD47 treatment of platelets did not further decrease the adhesion of anti-CD36-treated platelets and CD36 is a TSP-1 receptor, it appears that CD36/TSP-1 interaction could trigger the CD47-dependent pathway. Overall, CD47 antagonists may be potentially useful to inhibit platelet adhesion on inflamed endothelium.

The complex role of interleukin-10 in autoimmunity

Interleukin-10 (IL-10) is a cytokine that has been tested in different clinical trials based on its ability to down regulate T helper 1-type responses, namely IFN-gamma secretion and activation of monocytes/macrophages. There is also evidence in different animal models, that IL-10 could be useful in controlling Th2-mediated inflammatory processes. However, IL-10 also displays immunostimulatory properties especially on B cells and activated CD8(+)T cells. These seemingly divergent effects may explain the apparent lack of activity or adverse effects observed after IL-10 treatment in several animal models or clinical trials. Nevertheless, the ability of IL-10 to induce the differentiation of a subset of regulatory CD4(+)T cells (Tr1) and the importance of IL-10 for the in vivo function of regulatory T cells tends to support the view of IL-10 as a crucial cytokine in the control of immune responses. In different in vivo models, these cells were shown to inhibit Th1 and Th2-type inflammatory responses through the secretion of IL-10. These Tr1 cells may thus be used in specific cellular therapy in order to deliver IL-10 precisely at the site of inflammation.

Characterization of dendritic cells that induce tolerance and T regulatory 1 cell differentiation in vivo

Active suppression is mediated by a subpopulation of CD4(+) T cells that prevents autoimmunity. However, the mechanisms involved in their differentiation in vivo are currently under intensive research. Here we show that in vitro culture of bone marrow cells in the presence of IL-10 induces the differentiation of a distinct subset of dendritic cells with a specific expression of CD45RB. These CD11c(low)CD45RB(high) DCs are present in the spleen and lymph nodes of normal mice and are significantly enriched in the spleen of IL-10 Tg mice. These natural or in vitro-derived DCs display plasmacytoid morphology and an immature-like phenotype, and secrete high levels of IL-10 after activation. OVA peptide-pulsed CD11c(low)CD45RB(high) DCs specifically induce tolerance through the differentiation of Tr1 cells in vitro and in vivo. Our findings identify a natural DC subset that induces the differentiation of Tr1 cells and suggest their therapeutic use.

Differentiation of regulatory T cells 1 is induced by CD2 costimulation

Induction and maintenance of peripheral tolerance is an important phenomenon for the control of homeostasis in the immune system. There is now compelling evidence for CD4(+) T cells that prevent immune pathology, both in autoimmunity and in transplantation. However, the mechanisms involved in the specific differentiation of these T cells are unknown. We had previously shown that repetitive stimulations of naive T cells in the presence of IL-10 induce the differentiation of T regulatory cells 1. We further dissected the mechanism of IL-10 function and demonstrated that IL-10 acts by the down-regulation of most costimulatory molecules without modifying the expression of CD58. Using artificial APCs expressing various costimulatory molecules, we demonstrated that, in contrast to other costimulation patterns, costimulation via CD2 alone, in the absence of costimulations through CD28- or LFA-1, induced T cell anergy in an IL-10-independent pathway along with the differentiation of Ag-specific regulatory T cells. T regulatory cell-1 differentiation via CD2 was very efficient as both high IL-10 secretion and regulatory function were observed after the first stimulation of naive T cells with CD32-CD58 L cells. The possibility to rapidly induce the differentiation of Ag-specific regulatory T cells will certainly accelerate their characterization and their potential use as regulators of T cell-mediated diseases.

Regulation of TGF-beta response during T cell activation is modulated by IL-10

TGF-beta1 is an important pleiotropic cytokine that has been described to have both stimulatory and inhibitory effects on cell growth and differentiation. For several cell types, the effect of TGF-beta1 was found to correlate with the differentiation stage of the cells and the presence of other cytokines. In this report, we address the influence of TGF-beta1 on CD4(+) T cell activation by evaluating the effect of TGF-beta1 on the proliferative and cytokine responses of purified resting and activated human or mouse CD4(+) T cells. TGF-beta1 inhibits proliferation and cytokine secretion on resting CD4(+) T cells but has no inhibitory effect on activated T cells. Moreover, TGF-beta1 unresponsiveness of activated T cells was correlated with a down-regulation in the expression of the TGF-beta receptor type II. Interestingly, IL-10 addition enhances TGF-beta receptor type II expression and restores TGF-beta responsiveness on activated T cells. These results indicated that TGF-beta responsiveness is sequentially regulated on T cells by the modulation of the of TGF-beta receptor type II chain expression. Moreover, we have identified a novel regulatory role of IL-10 on TGF-beta-dependent T cell growth that can explain the control of T cell activation on chronic vs acute inflammatory sites.

T regulatory cells 1 inhibit a Th2-specific response in vivo

We recently described a new population of CD4(+) regulatory T cells (Tr1) that inhibits proliferative responses of bystander T cells and prevents colitis induction in vivo through the secretion of IL-10. IL-10, which had been primarily described as a Th2-specific cytokine inhibiting Th1 responses, has displayed in several models a more general immune suppression on both types of effector T cell responses. Using an immediate hypersensitivity model in which BALB/c mice immunized with OVA (alum) normally generate Th2-dominated responses, we examined the ability of OVA-specific Tr1 T cell clones to inhibit OVA-specific cytokines and Ab responses. In contrast to Th2 or Th1 T cell clones, transfer of Tr1 T cell clones coincident with OVA immunization inhibited Ag-specific serum IgE responses, whereas IgG1 and IgG2a synthesis were not affected. This specific inhibition was mediated in part through IL-10 secretion as anti-IL-10 receptor Abs treatment reverted the inhibitory effect of Tr1 T cell clones. Although specifically targeted to IgE responses, Tr1 clones' inhibitory effects were more profound as they affected Ag-specific Th2 cell priming both in term of proliferative responses and cytokine secretion. These results suggest that regulatory T cells may play a fundamental role in maintaining the balance of the immune system to prevent allergic disorders.

Can interleukin-10 be used as a true immunoregulatory cytokine?

Interleukin-10 (IL-10) is a cytokine that is currently regarded as a potential therapy for inflammatory diseases involving T helper 1-type responses because of its ability to downregulate several major functions of Th1 cells and macrophages. There are also evidence that IL-10 could be useful in controlling Th2-mediated inflammatory processes. However IL-10 has also immunostimulatory properties especially on B-cells and activated CD8+ T cells. These pleiotropic effects may explain the discrepancy observed after IL-10 treatment in different in vivo experimental models. We have recently shown that IL-10 induces the differentiation of a subset of regulatory CD4+ T cells (Tr1). In different in vivo models, these cells were shown to inhibit Th1 and Th2-type inflammatory responses through the secretion of IL-10. These Tr1 cells may thus be used in specific cellular therapy in order to deliver IL-10 precisely at the site of inflammation.

IL-10 transgenic mice present a defect in T cell development reminiscent of SCID patients

To analyze the effect of IL-10 overexpressed by APCs as observed in some SCID patients, we have expressed the human IL-10 cDNA under the control of the murine MHC class II promoter in transgenic mice. Similar to SCID patients, these mice presented a defect in T cell maturation characterized by a rapid thymic aplasia that started after birth. The blockage in T cell maturation was strictly restricted to TCR-alpha beta T cells as the absolute number of thymic dendritic, TCR-gamma delta and NK1.1 T cells were equivalent to control littermates. Crossing IL-10 transgenic mice with TCR transgenic mice or treatment with staphylococcal enterotoxin B showed that the defect was not related to the impairment of positive or negative selection. However, repopulating of IL-10 transgenic mouse-fetal thymic organ culture with different stages of triple negative T cells isolated from control mice showed that the blockage occurred specifically at the pre-T cell stage and was reverted by treatment with blocking anti-IL-10 mAbs. These results demonstrate that IL-10 regulates T cell maturation and that dysregulation of IL-10 expression can lead to severe T cell immunodeficiency.

Cellular immune responses of a Senegalese community recently exposed to Schistosoma mansoni: correlations of infection level with age and inflammatory cytokine production by soluble egg antigen-specific cells

A recently reported epidemic of Schistosoma mansoni infection in Senegal provided an opportunity to study the dynamics of the development of immunity to human schistosomiasis. We report here on the cell-mediated immune response in a population of 99 females and 95 males, with particular emphasis on the relationship between intensity of infection and age. We found that the intensity of infection correlated negatively with age in females but not in males. In men and women, both Th1- and Th2-type cytokines were detected upon in vitro stimulation of PBMCs with soluble egg antigen (SEA) or soluble adult worm antigens (SWAP). In the female group, SEA-induced PBMC proliferation was associated with the production of IFN-gamma, IL-2 and IL-5, all of which correlated negatively with intensity of infection. Most cytokine production correlated positively with age. Spontaneous production of TNF-alpha, IL-6 and IL-10 was higher in the infected population than in an uninfected control group. Our results suggest that immunity to infection could be more pronounced in the female population and associated with a Th0/1 + 2 pattern of cytokine secretion mediated by soluble egg antigen (SEA).

Depletion of eosinophils in mice through the use of antibodies specific for C-C chemokine receptor 3 (CCR3)

We have generated rat monoclonal antibodies specific for the mouse eotaxin receptor, C-C chemokine receptor 3 (CCR3). Several anti-CCR3 mAbs proved to be useful for in vivo depletion of CCR3-expressing cells and immunofluorescent staining. In vivo CCR3 mAbs of the IgG2b isotype substantially depleted blood eosinophil levels in Nippostrongyus brasiliensis-infected mice. Repeated anti-CCR3 mAb treatment in these mice significantly reduced tissue eosinophilia in the lung tissue and bronchoalveolar lavage fluid. Flow cytometry revealed that mCCR3 was expressed on eosinophils but not on stem cells, dendritic cells, or cells from the thymus, lymph node, or spleen of normal mice. Unlike human Th2 cells, mouse Th2 cells did not express detectable levels of CCR3 nor did they give a measurable response to eotaxin. None of the mAbs were antagonists or agonists of CCR3 calcium mobilization. To our knowledge, the antibodies described here are the first mAbs reported to be specific for mouse eosinophils and to be readily applicable for the detection, isolation, and in vivo depletion of eosinophils.

A transgenic model to analyze the immunoregulatory role of IL-10 secreted by antigen-presenting cells

IL-10 is a cytokine secreted by a wide variety of cells type that has pleiotropic stimulatory and suppressive activities on both lymphoid and myeloid cells in vitro. To analyze the consequences of high IL-10 secretion by APCs in immune responses, we produced transgenic mice expressing human IL-10 directed by the MHC class II Ea promoter. Despite alterations in the development of T and B cells, no gross abnormalities were detected in peripheral lymphocyte populations or serum Ig levels. However, when immunized using conditions that give either a Th2-type or a Th1-type response, IL-10 transgenic mice failed to mount a significant T or B cell immune response to OVA. IL-10 transgenic mice were also highly susceptible to infection with intracellular pathogens like Listeria monocytogenes or Leishmania major, in contrast to IL-10 transgenic mice, where the transgene was express in T cells. Finally, the recently described stimulatory effect of IL-10 on CD8+ T cells was confirmed by the ability of IL-10 transgenic mice to limit the growth of immunogenic tumors by a CTL-mediated mechanism. These results demonstrate, that, depending on the type of immune response, IL-10 can mediate immunosuppressive or immunostimulatory activities in vivo.

The induction of a protective response in Leishmania major-infected BALB/c mice with anti-CD40 mAb

A protective immune response to the intracellular parasite Leishmania major requires the development of a Th1 CD4+ T cell phenotype. We demonstrate herein that BALB/c mice, which normally develop a susceptible Th2 response to L. major infection, are protected when co-injected with an agonistic anti-murine CD40 mAb. Anti-CD40 mAb-mediated protection in this system was found to be T cell dependent, since it was not observed in C57BL/6 x 129 mice that were rendered T cell deficient (TCR beta-/- x TCR delta-/-) and L. major susceptible. Anti-CD40 mAb stimulation of L. major-infected BALB/c mice was accompanied by increased IL-12 and IFN-gamma production in draining lymph nodes, analyzed either by direct expression, or in an antigen-specific in vitro recall assay. The protective role of these cytokines was indicated by the finding that anti-CD40 mAb-mediated protection of L. major-infected BALB/c mice could be reversed by co-treating the animals with neutralizing anti-IL-12 and/or anti-IFN-gamma mAb. Collectively, these data suggest that BALB/c mice develop a protective Th1 CD4+ T cell response to L. major infection when co-injected with anti-CD40 mAb. While the CD40-CD40L interaction has been previously shown to be vital in the control of murine Leishmaniasis, the current study establishes in vivo that anti-CD40 mAb treatment alone is sufficient to protect BALB/c mice from L. major infection and raises the possibility of utilizing this approach for vaccination strategies.

Induction of human T helper cell type 1 differentiation results in loss of IFN-gamma receptor beta-chain expression

Differential expression of cytokine receptors accounts for an important regulatory mechanism in differentiation of Th1/Th2 subsets. Here, we report that human Th0 and Th2 clones constitutively express transcripts for the IFN-gammaR beta-chain, whereas mRNA for this signaling component of the IFN-gamma receptor is absent in Th1 clones. Activation of T cell clones, however, resulted in a transient induction or enhancement of IFN-gammaR beta-chain mRNA expression in Th1 clones and Th0/Th2 clones, respectively. IL-12-mediated Th1 cell differentiation of naive CD4+, CD45RA+ cord blood T cells, which constitutively express IFN-gammaR beta-chain mRNA, resulted in a loss of expression of this cytokine receptor chain after 6 to 12 days of culture. In contrast, Th2 populations, differentiated from CD4+, CD45RA+ cord blood T cells in the presence of IL-4, continued to express high levels of IFN-gammaR beta-chain transcripts. The loss of IFN-gammaR beta-chain expression in Th1 populations was accompanied by a failure of IFN-gamma to induce the expression of the IFN-gamma-inducible gene, IFN response factor-1, whereas IFN-gamma was effective in inducing IFN response factor-1 mRNA expression in Th0 and Th2 cells. These results indicate that down-regulation of the IFN-gammaR beta-chain correlates with impaired IFN-gamma-induced signaling in Th1 cells. Finally, Th2 populations, generated in the presence of both IL-4 and IFN-gamma, expressed levels of IFN-gammaR beta-chain transcripts similar to those produced by cells differentiated in the presence of IL-4 only, demonstrating that IFN-gamma does not modulate the expression of its receptor. Together, these data indicate that human Th0/Th2 and Th1 subsets, respectively, can be distinguished based on the expression of the IFN-gammaR beta-chain.

Induction of human T helper cell type 1 differentiation results in loss of IFN-gamma receptor beta-chain expression

Differential expression of cytokine receptors accounts for an important regulatory mechanism in differentiation of Th1/Th2 subsets. Here, we report that human Th0 and Th2 clones constitutively express transcripts for the IFN-gammaR beta-chain, whereas mRNA for this signaling component of the IFN-gamma receptor is absent in Th1 clones. Activation of T cell clones, however, resulted in a transient induction or enhancement of IFN-gammaR beta-chain mRNA expression in Th1 clones and Th0/Th2 clones, respectively. IL-12-mediated Th1 cell differentiation of naive CD4+, CD45RA+ cord blood T cells, which constitutively express IFN-gammaR beta-chain mRNA, resulted in a loss of expression of this cytokine receptor chain after 6 to 12 days of culture. In contrast, Th2 populations, differentiated from CD4+, CD45RA+ cord blood T cells in the presence of IL-4, continued to express high levels of IFN-gammaR beta-chain transcripts. The loss of IFN-gammaR beta-chain expression in Th1 populations was accompanied by a failure of IFN-gamma to induce the expression of the IFN-gamma-inducible gene, IFN response factor-1, whereas IFN-gamma was effective in inducing IFN response factor-1 mRNA expression in Th0 and Th2 cells. These results indicate that down-regulation of the IFN-gammaR beta-chain correlates with impaired IFN-gamma-induced signaling in Th1 cells. Finally, Th2 populations, generated in the presence of both IL-4 and IFN-gamma, expressed levels of IFN-gammaR beta-chain transcripts similar to those produced by cells differentiated in the presence of IL-4 only, demonstrating that IFN-gamma does not modulate the expression of its receptor. Together, these data indicate that human Th0/Th2 and Th1 subsets, respectively, can be distinguished based on the expression of the IFN-gammaR beta-chain.

Isolation and characterization of transformed human T-cell lines infected by Epstein-Barr virus

Epstein-Barr virus (EBV) is a human lymphotropic virus whose main targets have traditionally been described as B lymphocytes and epithelial cells. Here we report the isolation and characterization of largely monoclonal transformed human T-cell lines infected by EBV. The transformed T cells expressed CD2, CD3, and either CD4 or CD8 surface molecules and more generally displayed the phenotype of naive T cells with a complete and clonal rearrangement of the T-cell receptor. None of the cell lines expressed B cells, natural killer, or myeloid antigens or had immunoglobulins genes rearrangement. They grew in the absence of growth factor; however, they all secreted interleukin-2 after mitogenic activation. Polymerase chain reaction (PCR) analysis showed the presence of EBV DNA in all these cell lines. Moreover, Southern blot analysis of one of these cell lines shows the presence of circular episomic EBV DNA, and by Northern blot or reverse transcriptase-PCR analysis, only the expression of Epstein-Barr nuclear antigen-1 (EBNA-1) and latent membrane protein-1 (LMP-1) genes was detected. Finally, the complete transformed phenotype of this T-cell line was shown by its injection into nude or recombination activating gene 2 (RAG2)-deficient mice that led to the formation of solid tumors.

Priming of human CD4+ antigen-specific T cells to undergo apoptosis by HIV-infected monocytes. A two-step mechanism involving the gp120 molecule

The study of the pathology of HIV-1 infection in chimpanzees supports the idea of the crucial role of HIV-infected monocytes in the pathogenesis of AIDS, although viral mechanisms that lead to T cell dysfunction and deletion during HIV infection are still unclear. We show here that HIV-1-infected antigen-presenting monocytes (APCs) are able to prime in vitro non-HIV-infected antigen-specific CD4+ T cell lines or peripheral blood CD4+ T cells to undergo apoptosis after antigen-specific restimulation. The priming of T cells for apoptosis occurs in the absence of HIV replication in the T cells. Priming for apoptosis required two concomitant signals present on the same APC, an antigenic stimulus and a second signal provided by the HIV gp120 protein as demonstrated by the use as APCs of EBV-LCLs infected with different recombinant deleted proviruses or transfected with different HIV proteins. These results provide a mechanism for the priming for apoptosis of T cells in HIV-infected patients, implicating a role for HIV-infected APCs in the induction of T cell dysfunction and depletion in AIDS.

Selective CD4+ T cell deletion after specific activation in HIV-infected individuals; protection by anti-CD28 monoclonal antibodies

AIDS is characterized by a progressive decline in the number of CD4+ T cells. This is preceded by an early selective defect in the proliferation of these cells to recall antigens [1-3], pokeweed mitogen (PWM) [4-6] and to superantigens (SAg) [4,7]. In contrast, the proliferative response to phytohaemagglutinin (PHA) remains intact [1,2,5]. We and others have shown that the proliferative defect in response to some stimuli was in fact due to the induction of cell death [4,7]. The activation-induced cell death mechanism that explains the proliferative defects observed in vitro might also account for the progressive in vivo deletion of CD4+ T cells. Indeed, studies performed on different models of primates have shown that induction of cell death in CD4+ T cells was detected only when T cells were isolated from animals infected with a type of retrovirus that induces an AIDS-like disease [8]. This correlation prompted us to analyse further the mechanism of HIV-induced activation cell death to determine the specificity and rate of induction of cell death. T cells from HIV-infected individuals were activated with superantigens and the V beta T cell receptor (TCR) expression analysed. Data presented here show that cell death is restricted to activated CD4+ T cells, and does not affect bystander cells. More importantly, addition of anti-CD28 MoAb specifically inhibited the induction of apoptosis, raising possibilities for therapy.

Murine interleukin-4 production with baculovirus: an easy and rapid method for a small scale production of functional interleukins

We described a baculovirus expression system for high level production of secreted murine recombinant IL-4. We have constructed a recombinant baculovirus based on Autographa californica polyhedrosis virus, containing both a synthetic PCR-derived murine IL-4 cDNA under the control of the polyhedrin promoter and the lacZ gene under the control of the P10 promoter to allow an easy detection of recombinant virus. The baculovirus IL-4 was fully functional in biological assay and was present under two glycosylated forms in the supernatants of infected Sf9 cells. We also detected a third unglycosylated intracytoplasmic form resulting from a fusion between the 35 first amino acids of polyhedrin and the murine IL-4. Finally, confocal microscopy showed that this recombinant protein was secreted along a classical pathway like in mammalian cells.

Analysis of the V beta specificity of superantigen activation with a rapid and sensitive method using RT PCR and an automatic DNA analyser

Polymerase chain reaction (PCR) by the specific amplification of a DNA target sequence has been shown to permit analysis of T cell receptor usage. The complete repertoire is amplified using oligonucleotide primers specific for each of the known V alpha or V beta regions of the T cell receptor. One of the methods currently used to appreciate the relative quantity of different V chains of the TCR is by coamplifying in the same reaction tube the variable region of one chain together with the constant region of the other chain. We have optimised PCR conditions and analysed PCR products on an automatic DNA analyser facilitating the quantification of the amplified products, avoiding the use of radioisotopes, and allowing the determination of the sizes of CDR3 regions, thus giving new information on the modification of the T cell repertoire. This method was used to analyse the precise V beta specificity of the T cell activation with the superantigen SEB.

Obtention of a human primary humoral response against schistosome protective antigens in severe combined immunodeficiency mice after the transfer of human peripheral blood mononuclear cells

Peripheral blood mononuclear cells (PBMC) from healthy donors were injected into C.B.-17 severe combined immunodeficiency (scid) mice which were subsequently immunized with crude Schistosoma mansoni adult worm antigenic preparation (SWAP) or with recombinant S. mansoni 28-kDa glutathione transferase (r-Sm-28-GST) antigen. PBMC from a S. mansoni-infected patient were also transferred. The specific human anti-SWAP and anti-Sm-28-GST antibody responses were monitored. The presence in both cases of human specific antibodies in scid mouse sera was determined by enzyme-linked immunosorbent assay and Western blotting techniques using anti-human immunoglobulin reagents. No antibodies were detected in these sera using anti-mouse immunoglobulin antisera. These antibodies were functional since a cytotoxic activity against schistosomula was observed when monocytes were incubated with scid mouse sera positive for anti-Sm-28-GST antibodies.