B7-1 expression of Langerhans cells is up-regulated by proinflammatory cytokines, and is down-regulated by interferon-gamma or by interleukin-10

IL-3 induces B7.2 (CD86) expression and costimulatory activity in human eosinophils

Eosinophils in tissues are often present in intimate contact with T cells in allergic and parasitic diseases. Resting eosinophils do not express MHC class II proteins or costimulatory B7 molecules and fail to induce proliferation of T cells to Ags. IL-5 and GM-CSF induce MHC class II and B7 expression on eosinophils and have been reported in some studies to induce eosinophils to present Ag to T cells. The cytokine IL-3, like IL-5 and GM-CSF, is a survival and activating factor for eosinophils and the IL-3 receptor shares with the IL-5 and GM-CSF receptors a common signal transducing beta-chain. IL-3-treated eosinophils expressed HLA-DR and B7.2, but not B7.1 on their surface and supported T cell proliferation in response to the superantigen toxic shock syndrome toxin 1, as well as the proliferation of HLA-DR-restricted tetanus toxoid (TT) and influenza hemagglutinin-specific T cell clones to antigenic peptides. This was inhibited by anti-B7.2 mAb. In contrast, IL-3-treated eosinophils were unable to present native TT Ag to either resting or TT-specific cloned T cells. In parallel experiments, eosinophils treated with IL-5 or GM-CSF were also found to present superantigen and antigenic peptides, but not native Ag, to T cells. These results suggest that eosinophils are deficient in Ag processing and that this deficiency is not overcome by cytokines that signal via the beta-chain. Nevertheless, our findings suggest that eosinophils activated by IL-3 may contribute to T cell activation in allergic and parasitic diseases by presenting superantigens and peptides to T cells.

Enhanced contact hypersensitivity in human monocyte chemoattractant protein-1 transgenic mouse

Monocyte chemoattractant protein (MCP)-1 is a chemotactic cytokine for monocytes, memoryT cells and dendritic cells (DC). However, the precise role of MCP-1 in a variety of immunological responses remains unclear. In the present study, we analyzed contact hypersensitivity (CHS) using human MCP-1 transgenic mice (hMCP-1Tgm) that constitutively produce high levels of hMCP-1 in the sera. Following 2,4-dinitrofluorobenzene (DNFB) sensitization, enhancement of CHS was demonstrated in Tgm as compared with that in non-Tgm. Anti-hMCP-1 antibodies significantly inhibited the CHS in Tgm. A prominent accumulation of B7-1+I-Ad+ Langerhans' cells (LC) bearing haptens was detected in draining lymph nodes (DLN) of Tgm 24 h after DNFB or fluorescein isothiocyanate (FITC) sensitization. Similar results were obtained with BALB/c mice administrated recombinant (r) hMCP-1. Langerhans' cells (LC) in the epidermal sheets of Tgm increased in size and expressed high levels of I-Ad and B7-1 12 h after FITC application compared with those of non-Tgm. After 18 h, the number of LC in the epidermis was reduced in Tgm. It was also shown that the B7-1 expression on LC of BALB/c mice was augmented after culture with rhMCP-1. These findings demonstrate that MCP-1 not only accelerates LC migration from epidermis into the DLN after sensitization with haptens but also up-regulates the I-Ad and B7-1 expressions, which results in the enhanced T cell activation and CHS.

IL-10 improves skin disease and modulates endothelial activation and leukocyte effector function in patients with psoriatic arthritis

Psoriatic arthritis (PsA) provides an ideal disease model in which to investigate the bioactivities of potentially therapeutic cytokines at multiple sites of tissue inflammation. We investigated the effects of IL-10, an antiinflammatory cytokine, given s.c. for 28 days in a double-blind, placebo-controlled study in PsA patients. Synovial/skin biopsies, peripheral blood leukocytes, articular magnetic resonance images, and clinical disease activity scores were obtained sequentially. Modest, but significant clinical improvement in skin, but not articular disease activity scores with only minor adverse effects was observed. Type 1, but not type 2 T cell cytokine production in vitro was suppressed in human rIL-10 compared with placebo recipients. Similarly, monokine production in vitro was reduced, whereas serum soluble TNFRII levels were elevated, indicating suppression of monocyte function. Decreased T cell and macrophage infiltration in synovial tissues was accompanied by reduced P-selectin expression. Moreover, suppressed synovial enhancement on magnetic resonance imaging and reduced alpha(v)beta(3) integrin expression on von Willebrand factor(+) vessels were observed. Together these data demonstrate that a short course of IL-10 modulates immune responses in vivo via diverse effects on endothelial activation, and leukocyte recruitment and effector function. Such biological changes may result in clinically meaningful improvement in disease activity.

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.

Peripheral T-cell tolerance defined through transgenic mouse studies

Selection in the thymus restricted by MHC and self-peptide shapes the diverse reactivities of the T-cell population which subsequently seeds into the peripheral tissues, in anticipation of the universe of pathogen antigens to which the organism may be exposed. A necessary corollary is the potential for T-cell self-reactivity (autoimmunity) in the periphery. Transgenic mouse models in which transgene expression in the thymus is prevented or excluded, have been particularly useful for determining the immunological outcome when T-cells encounter transgene-encoded 'self' antigen in peripheral tissues. Data suggest that non-mutually exclusive mechanisms of T-cells 'ignoring' self-antigen, T-cell deletion, T-cell anergy and T-cell immunoregulation have evolved to prevent self-reactivity while maintaining T-cell diversity. The peripheral T-cell repertoire, far from being static following maturation through the thymus, is in a dynamic stated determined by these peripheral selective and immunoregulatory influences. This article reviews the evidence with particular reference to CD8+ive T-cells.

Dendritic cells as a tool to induce anergic and 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. As well as their stimulatory functions, there is growing evidence that dendritic cells, acting as professional antigen-presenting cells, also maintain and regulate T-cell tolerance in the periphery. This control function is exerted by certain maturation stages and subsets of different ontogeny, and can be influenced by immunomodulatory agents. What is the current state of knowledge of the "immunoregulatory" properties of dendritic cells and how might tolerance-inducing dendritic cells be relevant to therapeutic applications in humans?

Suppression of T(h)1 cell activation and prevention of autoimmune diabetes in NOD mice by local expression of viral IL-10

Insulin-dependent diabetes mellitus in the NOD mouse model is caused by the T cell-mediated autoimmune destruction of pancreatic beta cells. Viral IL-10 (vIL-10), encoded in the Epstein-Barr virus genome, shares many of the anti-inflammatory properties of cellular IL-10, but lacks its immunostimulatory properties. In the present study, we generated transgenic (Tg) NOD mice in which vIL-10 was produced exclusively in pancreatic islets and investigated the effect of vIL-10 on the development of diabetes. The accumulation of lymphocytes around islets was more prominent, but the invasive insulitis decreased in the vIL-10 Tg mice. The incidence of diabetes was markedly reduced in the vIL-10 Tg mice, in clear contrast to the accelerated diabetes seen in the murine IL-10 Tg NOD mice. IL-12p40 and IFN-gamma mRNA levels were decreased in pancreata of the vIL-10 Tg mice, although CD4 mRNA level was markedly increased. These results suggest that locally produced vIL-10 induced leukocyte migration, but inhibited the activation of T(h)1, probably through suppressing the production of IL-12. They indicate that vIL-10 may well be superior to cellular IL-10 in the treatment of autoimmune diabetes. The vIL-10 Tg NOD mice should provide a useful tool for understanding the differential action of vIL-10 versus cellular IL-10.

Acquisition of immune function during the development of the Langerhans cell network in neonatal mice

The immunological function of the Langerhans cell (LC) network in neonatal skin was examined by defining the development of cutaneous immunity relative to the structure, phenotype and function of the epidermal LC network in neonatal, juvenile and adult mice. Analysis of epidermal sheets showed the presence of major histocompatibility complex (MHC) II+, multilectin receptor DEC-205- cells within the epidermis of 3-day-old mice; both cell density and DEC-205 expression increased until day 14. When visualized with antibodies directed at MHC II, the network was poorly formed in 3- and 7-day-old mice, as there was a lower cell density and poor MHC II expression on dendritic processes, compared to mice at day14. Application of a fluorescent antigen to 3-day-old mice revealed that the LC were inefficient in transporting antigen to the draining lymph node. There was an improvement at day 7 and by day 14 comparable numbers of antigen carrying cells were detected in the lymph nodes of 6-week-old mice. The reduced antigen carriage in 3- and 7-day-old mice correlated with a poor contact sensitivity response. This was not simply due to failure to present antigen, but development of immunosuppression, as transfer of T cells from adult mice that were previously treated with antigen when they were 3 days old, to adult recipients resulted in antigen specific immunosuppression. Analysis of CD80 and CD86 expression showed that LC from day 3 skin expressed CD80, but not CD86 and application of antigen through this skin was inefficient in upregulating CD86. These findings indicate that when the neonatal LC network is poorly developed it is functionally immature and antigen applied through this 'functionally immature network' results in antigen specific immunosuppression.

Generation of dendritic cells: role of cytokines and potential clinical applications

Over the last decade there has been great interest in generating populations of antigen presenting cells (APC), which can be exploited to improve immune responses to a variety of diseases including malignancies. Dendritic cells (DC) are an APC population that are easily generated ex vivo using a variety of cytokines. Cytokines can also be used to further manipulate these cells in maturation and function. The following discussion will provide an overview of dendritic cell isolation and generation with a focus on the role cytokines play in this process.

Effects of cytokines on the culture and differentiation of dendritic cells in vitro

The ability to culture dendritic cells (DC) in vitro has been integral to the dramatic increase in research in the area of immunotherapy. Over time, a number of methods for generating these cells have been developed. This article will provide an overview of the isolation and generation of DC and will give a detailed description of the role specific cytokines play in this process from the mobilization of precursors to the final maturation of DC.

IL-10 converts human dendritic cells into macrophage-like cells with increased antibacterial activity against virulent Mycobacterium tuberculosis

Dendritic cells (DC) are unique in their ability to initiate a primary immune response by the presentation of soluble Ags to T cells. Recent studies have shown that DC also phagocytose particulate Ags including the intracellular pathogen Mycobacterium tuberculosis. However, it is not known whether DC contain the growth of intracellular organisms or allow unlimited replication. To address this question, we infected human DC with a virulent strain of M. tuberculosis and monitored the intracellular growth. The bacteria grew two orders of magnitude within 7 days of culture. Among cytokines known to modulate mycobacterial growth particularly in murine macrophages (TNF-alpha, IFN-gamma, TGF-beta, IL-4), only IL-10 modulated the growth in human DC. This effect was specific for immature dendritic cells, as IL-10 did not induce growth inhibition in human macrophages. In searching for the mechanism of growth inhibition, we found that IL-10 induces the down-regulation of the DC marker CD1, while the macrophage marker CD14 was up-regulated. Functionally, IL-10-treated cells had a reduced capacity to induce an alloresponse, but phagocytic uptake of M. tuberculosis was more efficient. We also show that DC are inferior to macrophages in containing mycobacterial growth. These findings show that IL-10 converts DC into macrophage-like cells, thereby inducing the growth inhibition of an intracellular pathogen. At the site of a local immune response, such as a tuberculous granuloma, IL-10 might therefore participate in the composition of the cellular microenvironment by affecting the maturity and function of DC.

Interleukin 10 modulation of tumour necrosis factor receptors requires tyrosine kinases but not the PI 3-kinase/p70 S6 kinase pathway

We have previously shown that interleukin (IL-)10-induced proliferation of the murine mast cell line D36, was dependent upon the activation of PI 3-kinase and p70 S6 kinase. Conversely, we were able to show that this pathway was not involved in the signal transduction pathway mediating IL-10 inhibition of pro-inflammatory cytokine release from monocytes. We have extended these studies to investigate the induction of p75 tumour necrosis factor receptor (TNF-R) shedding, another anti-inflammatory property of IL-10. Using the inhibitors of PI 3-kinase (LY294002 and wortmannin) and an inhibitor of p70 S6 kinase activation (rapamycin), we were able to show that this anti-inflammatory effect of IL-10 was not mediated by the PI 3-kinase/p70 S6 kinase pathway, indicating that another signalling cascade(s) was involved. Further studies also investigated the role of tyrosine kinases in the response to IL-10. Two distinct tyrosine kinase inhibitors, herbimycin and genistein affected the expression of TNF-R in response to IL-10 but, surprisingly, with opposite effects. However, both compounds inhibited the activation of both PI 3-kinase and p70 S6 kinase, with a concomitant inhibition of IL-10-induced proliferation. We observed that whilst tyrosine kinase activity was involved in the regulation of TNF-R expression, IL-10-induced activation of JAK kinases was not sensitive to inhibition by the tyrosine kinase inhibitors. These data suggest that multiple unknown tyrosine kinases are mediating the IL-10-induced signal transduction pathways leading to the regulation of TNF-R expression and IL-10-induced proliferation.

Granulocyte/macrophage colony-stimulating factor inhibits IL-12 production of mouse Langerhans cells

We investigated the capacity of mouse Langerhans cells (LC) to produce IL-12, a central cytokine in a Th1 type of immune responses. We prepared purified LC (>95%) from BALB/c mouse skin by the panning method using anti-I-Ad mAb. An ELISA showed that purified LC spontaneously produced IL-12 p40, and that its production was up-regulated following simultaneous stimulation with anti-CD40 mAb and IFN-gamma. Surprisingly, GM-CSF strikingly inhibited IL-12 p40 production by anti-CD40/IFN-gamma-stimulated LC (% inhibition = 97.0 +/- 0.9% at 1 ng/ml GM-CSF). Supernatants of 48-h cultured keratinocytes (KC) also caused the inhibition of LC IL-12 p40 secretion, and this effect was neutralized by anti-GM-CSF mAb. IL-1alpha (1 ng/ml)-stimulated KC produced much more GM-CSF than unstimulated KC (60.9 +/- 0.2 pg/ml vs 20.9 +/- 1.7 pg/ml), and IL-1alpha-stimulated KC supernatants strongly inhibited IL-12 p40 production by anti-CD40/IFN-gamma-stimulated LC (% inhibition = 89.4 +/- 1.4%). A bioassay using an IL-12-dependent T cell line demonstrated the correlation of the level of IL-12 p40 with the bioactivity of IL-12. These results provide important implications for the pathogenesis of atopic dermatitis, which involves the participation of LC and KC with the capacity to produce IL-12 and GM-CSF, respectively.

Transgenic expression of granulocyte-macrophage colony-stimulating factor induces the differentiation and activation of a novel dendritic cell population in the lung

The role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the differentiation of dendritic cells (DCs) during pulmonary viral infection was investigated by using a mouse model of GM-CSF transgene expression established with an adenoviral vector (AdGM-CSF). GM-CSF gene transfer resulted in increased levels of GM-CSF in the lung, which peaked at day 4 and remained increased up to day 19. A striking cellular response composed predominantly of macrophage-like cells was observed in the lung receiving AdGM-CSF but not control vector. By FACS analysis, the majority of these cells were identified at an early time point as macrophages and later as mature/activated myeloid DCs characterized by CD11bbright, CD11cbright, MHC class IIbright, and B7.1bright. In contrast, GM-CSF had a weak effect on a small DC population that was found present in normal lung and was characterized by CD11cbright and CD11blow. By immunohistochemistry staining for MHC II, the majority of activated antigen-presenting cells were localized to the airway epithelium and peribronchial/perivascular areas in the lung. A concurrently enhanced Th1 immune response was observed under these conditions. The number of CD4 and CD8 T cells was markedly increased in the lung expressing GM-CSF, accompanied by increased release of interferon (IFN)γ in the lung. Furthermore, lymphocytes isolated from either lung parenchyma or local draining lymph nodes of these mice but not the control mice released large amounts of IFNγ on adenoviral antigen stimulation in vitro. These findings reveal that GM-CSF promotes the differentiation and activation of a myeloid DC population primarily by acting on macrophages during pulmonary immune responses.

Transgenic expression of granulocyte-macrophage colony-stimulating factor induces the differentiation and activation of a novel dendritic cell population in the lung

The role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the differentiation of dendritic cells (DCs) during pulmonary viral infection was investigated by using a mouse model of GM-CSF transgene expression established with an adenoviral vector (AdGM-CSF). GM-CSF gene transfer resulted in increased levels of GM-CSF in the lung, which peaked at day 4 and remained increased up to day 19. A striking cellular response composed predominantly of macrophage-like cells was observed in the lung receiving AdGM-CSF but not control vector. By FACS analysis, the majority of these cells were identified at an early time point as macrophages and later as mature/activated myeloid DCs characterized by CD11bbright, CD11cbright, MHC class IIbright, and B7.1bright. In contrast, GM-CSF had a weak effect on a small DC population that was found present in normal lung and was characterized by CD11cbright and CD11blow. By immunohistochemistry staining for MHC II, the majority of activated antigen-presenting cells were localized to the airway epithelium and peribronchial/perivascular areas in the lung. A concurrently enhanced Th1 immune response was observed under these conditions. The number of CD4 and CD8 T cells was markedly increased in the lung expressing GM-CSF, accompanied by increased release of interferon (IFN)γ in the lung. Furthermore, lymphocytes isolated from either lung parenchyma or local draining lymph nodes of these mice but not the control mice released large amounts of IFNγ on adenoviral antigen stimulation in vitro. These findings reveal that GM-CSF promotes the differentiation and activation of a myeloid DC population primarily by acting on macrophages during pulmonary immune responses.

Cytokines and chemokines in the initiation and regulation of epidermal Langerhans cell mobilization

Langerhans cells (LC) are members of the wider family of dendritic cells. LC reside in the epidermis where they serve as sentinels of the immune system, their responsibilities being to sample the external environment for changes and challenges and to deliver information (antigen) to responsive T lymphocytes within skin draining lymph nodes. The ability of LC to migrate from the epidermis to regional lymph nodes is therefore of pivotal importance to the induction of cutaneous immune responses. The journey that LC have to make from the skin has a number of requirements. Initially it is necessary that LC disassociate themselves from surrounding keratinocytes and are liberated from other influences that encourage their retention in the epidermis. Subsequently, migrating LC must successfully traverse the basement membrane of the dermal-epidermal junction and make their way, via afferent lymphatics, to draining lymph nodes. Effective entry into lymph nodes is necessary, as is correct positioning of cells within the paracortex. There is increasing evidence that both cytokines and chemokines, and their interaction with appropriate receptors expressed by LC, orchestrate the mobilization and movement of these cells. We here consider the parts played by these molecules, and how collectively they induce and direct LC migration.

Differential effects of cytokines and immunosuppressive drugs on CD40, B7-1, and B7-2 expression on purified epidermal Langerhans cells1

Langerhans cells are MHC class II antigen-positive antigen-presenting cells in the epidermis. Recent studies have revealed that Langerhans cells express costimulatory molecules like B7-1 and B7-2 and the accessory molecule CD40. Although these molecules are important for the antigen-presenting function of Langerhans cells, little is known about the precise regulation of their expression on purified Langerhans cells. Using a panning technique, we purified epidermal Langerhans cells to around 95% purity. Freshly prepared Langerhans cells (fLC) expressed the mRNA for receptors for M-CSF (cfms), GM-CSF (GM-CSFR), and TNF-alpha (TNFRII). TNF-alpha markedly upregulated CD40 and B7-1 expression on Langerhans cells, but not B7-2 expression. GM-CSF moderately upregulated B7-1 and B7-2 expression, and slightly upregulated CD40 expression. M-CSF moderately upregulated B7-1 expression, but did not modulate CD40 or B7-2 expression. Dexamethasone (DEX) markedly inhibited CD40, B7-1, and B7-2 expression on Langerhans cells. Cyclosporin A (CsA) and FK506 slightly inhibited CD40 and B7-1 expression on Langerhans cells, but not B7-2. Furthermore, TNF-alpha restored the DEX-induced inhibition of CD40 expression on Langerhans cells, but not the inhibition of B7-1 or B7-2 expression. GM-CSF restored DEX-induced inhibition of CD40, B7-1, and B7-2 expression. M-CSF did not affect the DEX-induced inhibition of these molecule expressions. These data provide a better understanding of the role of selective cytokines and immunosupressive drugs in the modulation of the antigen-presenting capacity of Langerhans cells.

Differential Modulation of Human Epidermal Langerhans Cell Maturation by Ultraviolet B Radiation

UVB irradiation of the skin causes immunosuppression and Ag-specific tolerance in which Langerhans cells (LC) are involved. We tested the effect of UVB on LC that had migrated out of cultured epidermal sheets derived from the skin that was irradiated ex vivo (200, 400, 800, or 1600 J/m2). Two separate subpopulations of LC were distinguished: large-sized LC with high HLA-DR expression, and HLA-DR-low, small LC. UVB stimulated the maturation of the former LC subset as demonstrated by enhanced up-regulation of CD80, CD86, CD54, CD40, and CD83 and reduced CD1a expression in comparison with unirradiated controls. In contrast, the latter LC exhibited little or no up-regulation of these molecules except for high CD1a expression and high binding of annexin V, indicating that they were apoptotic, although their CD95 expression was relatively low. Stimulation of enriched LC with CD40 ligand-transfected cells and IFN-γ revealed that the release of IL-1β, IL-6, IL-8, and TNF-α was enhanced by UVB. In comparison with HLA-DR-low LC, HLA-DR-high LC were the principal IL-8 producers as demonstrated by intracellular cytokine staining, and they retained more accessory function. There was no detectable secretion of IL-12 p70, and IL-18 production was neither affected by any stimulus nor by UVB. These results suggest a dual action of UVB on LC when irradiated in situ: 1) immunosuppression by preventing maturation and inducing apoptotic cell death in part of LC, and 2) immunopotentiation by enhancing the up-regulation of costimulatory molecules and the production of proinflammatory cytokines in another part.

T Cell-Derived IL-10 Promotes Lung Cancer Growth by Suppressing Both T Cell and APC Function

We have found previously that human lung cancers potently induce T lymphocyte IL-10 production in vitro. To assess the impact of enhanced T cell-derived IL-10 on antitumor immunity in vivo, we utilized transgenic mice expressing IL-10 under the control of the IL-2 promoter. We have shown previously that Lewis lung carcinoma cells (3LL) have more aggressive growth potential in IL-10 transgenic mice compared with control littermates. In this study, we show that transfer of T cells from IL-10 transgenic mice to control littermates transferred the IL-10 immunosuppressive effect and led to enhanced 3LL tumor growth. In addition to changes in T cell-mediated immunity, professional APC from IL-10 transgenic mice were found to have significantly suppressed capacity to induce MHC alloreactivity, CTL responses, and IL-12 production. Tumor Ag-pulsed dendritic cells from IL-10 transgenic mice also failed to generate antitumor reactivity. These results suggest that increased levels of T cell-derived IL-10 severely impair antitumor immunity in vivo, due to defects in both T cell and APC function.

Regulatory T cells and inflammatory bowel disease

Recent studies have identified interleukin 10 as a differentiation factor for a novel subset of immune suppressive regulatory T cells. Here, Hervé Groux and Fiona Powrie discuss the role that these cells play in the regulation of immune responses to enteric antigens and suggest that a deficiency in these cells might be involved in the pathogenesis of inflammatory bowel disease.

Evidence That Langerhans Cells in Adult Pulmonary Langerhans Cell Histiocytosis Are Mature Dendritic Cells: Importance of the Cytokine Microenvironment

Because Langerhans cells (LC) in peripheral tissues are generally “immature” cells with poor lymphostimulatory activity, the contribution of immune responses initiated by LC to the pathogenesis of pulmonary LC histiocytosis (LCH) has been uncertain. In this study we demonstrate that LC accumulating in LCH granulomas are phenotypically similar to mature lymphostimulatory dendritic cells present in lymphoid organs. LC in LCH granulomas intensely expressed B7-1 and B7-2 molecules, whereas normal pulmonary LC and LC accumulating in other pathologic lung disorders did not express these costimulatory molecules. The presence of B7+ LC in LCH granulomas was associated with the expression in these lesions, but not at other sites in the lung, of a unique profile of cytokines (presence of GM-CSF, TNF-α, and IL-1β and the absence of IL-10) that is known to promote the in vitro differentiation of LC into cells expressing a lymphostimulatory phenotype. Finally, LCH granulomas were the only site where CD154-positive T cells could be identified in close contact with LC intensely expressing CD40 Ags. Taken together, these results strongly support the idea that an abnormal immune response initiated by LC may participate in the pathogenesis of pulmonary LCH, and suggest that therapeutic strategies aimed at modifying the lymphostimulatory phenotype of LC may be useful in the treatment of this disorder.

T cell stimulation upon long-term secretion of viral IL-10

Viral IL-10 (vIL-10), the IL-10 homologue of Epstein-Barr virus, has so far been described as a cytokine that solely inhibits T cell function. Here we show in vivo and in vitro that after long-term secretion vIL-10 has a stimulatory effect on T cells. For this purpose we employed transfectants derived from a mastocytoma cell line (P815 cells, H-2(d)) constitutively secreting vIL-10 (P815-vIL-10) or expressing the co-stimulatory molecule B7-1 (P815-B7). After in vitro stimulation of splenocytes from syngeneic DBA/2 mice for 7 days in the presence of P815-vIL-10 cells we could detect a marked reduction of proliferation as well as cytotoxicity against P815 target cells. However, this inhibitory effect was reversed when stimulation with P815-vIL-10 cells was extended to 14 days. In vivo P815-vIL-10 cells were rejected whereas P815 cells transfected with a control plasmic were tumorigenic after injection into syngeneic DBA/2 mice. Furthermore, this stimulatory effect of constitutive vIL-10 secretion could be exploited to irradicate already established P815 tumors which were smaller than 5 x 5 mm. In contrast, paracrine vIL-10 secretion for a limited time period of 8 - 9 days was associated with inhibitory effects in vivo: P815-B7 cells, which are normally eliminated in DBA/2 mice, could grow if exposed to temporarily secreted vIL-10. These time-dependent immunomodulatory effects have to be considered in potential therapeutic applications of vIL-10.

IL-10 Transgenic Mice Present a Defect in T Cell Development Reminiscent to 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-αβ T cells as the absolute number of thymic dendritic, TCR-γδ 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.

The role of B7 costimulation in T-cell immunity

CD4+ T cells are considered to be the major controlling element of the adaptive immune response. They recognize foreign peptides by interaction of the T cell receptor (TCR) with peptide complexed to major histocompatibility complex (MHC) class II molecules on the surface of antigen presenting cells (APC). Once activated, CD4+ T cells orchestrate the various phases of the immune response. They are responsible for the production of numerous cytokines, which activate specific immune effector cell populations including B cells, eosinophils, mast cells and macrophages. Not surprisingly, the activation of CD4+ T cells needs to be tightly regulated and is subject to finely tuned control mechanisms. The requirement for a second or 'costimulatory' signal, in addition to the antigenic signal, provides a key element for the exquisite control of T cell activation. One of the major signalling pathways responsible for delivery of this costimulatory signal is induced by interaction of CD28 on T cells with B7 molecules found only on APC. The present review outlines our current understanding of the physiological role of B7 costimulatory signals in regulating CD4+ T cell responses.

Evidence for conformationally different states of interleukin-10: binding of a neutralizing antibody enhances accessibility of a hidden epitope

We present the mapping of two anti-human interleukin-10 (hIL-10) antibodies (CB/RS/2 and CB/RS/11) which have been described as binding their antigen cooperatively. The epitopes were identified using hIL-10-derived overlapping peptide scans prepared by spot synthesis. To identify residues essential for binding within the two epitopes, each position was replaced by all other L-amino acids. The epitope-derived peptides were further characterized with respect to antibody affinity and their inhibition of the antibody-hIL-10 interaction. One antibody (CB/RS/11) binds to residues which are completely buried in the X-ray structure of IL-10. Accessibility of this hidden epitope is enhanced upon binding of the antibody CB/RS/2, which recognizes a discontinuous epitope located nearby. The recognition of the hidden CB/RS/11 epitope, as well as the cooperative binding behaviour of the two antibodies, provides evidence that IL-10 can adopt a conformational state other than that observed in the crystal structure.

Differential expression and modulation of costimulatory molecules CD80 and CD86 on monocytes from patients with systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE) were recently shown to be defective in costimulatory molecule CD80 (B7-1) expression on antigen-presenting cells. This study was undertaken to further investigate the expression and cytokine regulation of both CD80 and CD86 (B7-2) on monocytes from patients with SLE. Freshly isolated and in vitro cytokine-stimulated peripheral blood mononuclear cells from 13 patients with SLE and 10 healthy subjects were analysed, cytometrically with dual-fluorescence staining, to detect expression of CD80 and CD86 in the CD14+ monocyte population. The results showed that, as in normal individuals, an overwhelming majority (95.62+/-3.54%) of monocytes from patients with SLE expressed the CD86 molecule, but only a few monocytes (5.54+/-4.36%) had detectable CD80 expression. The effects of interleukin-10 (IL-10) on the expression of CD80 and CD86 on monocytes from patients with SLE and normal controls were similar. IL-10 down-regulated the expression of CD86 while it slightly enhanced that of CD80. Interferon-gamma (IFN-gamma) increased both CD80 and CD86 expression on monocytes from both SLE patients and normal groups, albeit less significantly in the former than in the latter, i.e. CD80: 142.84+/-65.99% versus 226.08+/-78.90%, P<0.05; and CD86: 72.55+/-74.23% versus 153.99+/-94.14%, P<0.05, when expressed as percentage modulation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) showed a capacity for up-regulation of CD80 and CD86 expression on monocytes, of a magnitude that was similar both in patients with SLE and in normal subjects. We concluded that CD80 and CD86 were differentially expressed and modulated on monocytes and the defective IFN-gamma-induced up-regulation of CD80 and CD86 expression on SLE monocytes might be a factor in the pathogenesis of SLE.

Induction of immunologic tolerance for transplantation

In the second half of the 20th century, the transplantation of replacement organs and tissues to cure disease has become a clinical reality. Success has been achieved as a direct result of progress in understanding the cellular and molecular biology of the immune system. This understanding has led to the development of immunosuppressive pharmaceuticals that are part of nearly every transplantation procedure. All such drugs are toxic to some degree, however, and their chronic use, mandatory in transplantation, predisposes the patient to the development of infection and cancer. In addition, many of them may have deleterious long-term effects on the function of grafts. New immunosuppressive agents are constantly under development, but organ transplantation remains a therapy that requires patients to choose between the risks of their primary illness and its treatment on the one hand, and the risks of life-long systemic immunosuppression on the other. Alternatives to immunosuppression include modulation of donor grafts to reduce immunogenicity, removal of passenger leukocytes, transplantation into immunologically privileged sites like the testis or thymus, encapsulation of tissue, and the induction of a state of immunologic tolerance. It is the last of these alternatives that has, perhaps, the most promise and most generic applicability as a future therapy. Recent reports documenting long-term graft survival in the absence of immunosuppression suggest that tolerance-based therapies may soon become a clinical reality. Of particular interest to our laboratory are transplantation strategies that focus on the induction of donor-specific T-cell unresponsiveness. The basic biology, protocols, experimental outcomes, and clinical implications of tolerance-based transplantation are the focus of this review.

Importance of B7-1-Expressing Host Antigen-Presenting Cells for the Eradication of B7-2 Transfected P815 Tumor Cells

We have previously shown that B7-2 (CD86)-transfected P815 tumor cells elicit tumor-eradicating immunity that leads to the regression of the B7-2+ P815 tumor after transient growth in normal DBA/2 mice. Here, we show that both the B7-2 and B7-1 (CD80) molecules contribute to the eradication of B7-2+ P815 tumors as treatment of the mice with both anti-B7-2 and anti-B7-1 mAb was required to prevent B7-2+ P815 tumor regression. The cells that expressed the B7-1 molecule following inoculation of B7-2+ P815 tumor cells into normal mice were not the tumor cells but rather host APCs including MAC-1+ cells present in the draining lymph nodes. Moreover, B7-1-expressing host APCs were found to be important for the rejection of B7-2+ P815 tumors as anti-B7-2 mAb alone, which was ineffective in preventing B7-2+ P815 tumor rejection by normal wild-type mice, was effective in preventing B7-2+ P815 tumor rejection by mice in which the B7-1 gene was disrupted. Finally, consistent with the importance of B7-1-expressing host APCs for the generation of tumor-eradicating immunity against B7-2+ P815 tumor cells, CD4+ T cells (not only CD8+ T cells) were found to participate in tumor-eradicating immunity against B7-2+ P815 tumor cells. Thus, in addition to eliciting tumor-eradicating immunity directly, B7-2+ P815 tumor cells elicit tumor-eradicating immunity indirectly through B7-1-expressing host APCs that present tumor-associated Ags to CD4+ T cells.

Developmental regulation by cytokines of bone marrow-derived dendritic cells and epidermal Langerhans cells

Dendritic cells (DC) are specialized antigen-presenting cells involved in T cell-mediated immune responses. Differentiation and functional maturation of the DC are now known to be regulated by various cytokines, including TGF-beta1. The experiments of this study examined the effect of other cytokines, such as IL-4, IL-10 and IL-6, on the differentiation and maturation of bone marrow (BM)-derived DC (BM-DC) and epidermal Langerhans cells (LC). When IL-6 or IL-10 was added to cultures of BM cells in the presence of GM-CSF, both cytokines, as in the case of TGF-beta1, suppressed the maturation of DC in terms of the expression of adhesion and costimulatory molecules and T cell-stimulating activity. In contrast, IL-4 was not suppressive but rather supportive for the differentiation of DC. However, these suppressive cytokines hardly counteracted the maturation-inducing activity of TNF-alpha when added to cultures of immature DC. In addition, they appeared to block the overmaturation of DC, which is characterized by a loss of MHC class II molecules. Regarding LC maturation in epidermal cell cultures, IL-6 and IL-10 were inhibitory for the expression of CD86 and CD80 in a dose-dependent fashion. Unlike BM-DC, LC maturation was slightly enhanced by TGF-beta1. The protein antigen-presentation by LC to Th1 clone was not affected by IL-6, but slightly reduced by IL-10. These results suggest that each cytokine contributes to regulate the differentiation and maturation of DC at a different developmental stage.

Interleukin-10 increases mannose receptor expression and endocytic activity in monocyte-derived dendritic cells

Human monocyte-derived dendritic cells were differentiated in vitro for 7 days with granulocyte macrophage-colony stimulating factor and interleukin-13. These cultured dendritic cells are at an immature stage of differentiation and exhert high endocytic activity via surface mannose receptor and via fluid-phase macropinocytosis. We have investigated the modulation of endocytosis by interleukin-10 in these cells. When added during the last 24 h of the 7-day culture, interleukin-10 significantly stimulated the uptake of fluorescein-labelled dextran (39 +/- 16% increase, mean +/- SD of 6 experiments), a sugar binding to the mannose receptor. This effect was dose dependent and correlated with the length of exposure to interleukin-10, with a maximal effect (more than seven-fold increase) when the cytokine was added at the beginning of the culture (day 0). The interleukin-10-increased fluorescein-labelled-dextran endocytosis was mostly mediated via the mannose receptor, as unlabelled mannose and specific antimannose receptor monoclonal antibody inhibited most of the uptake. Moreover, interleukin-10-treated cells expressed increased levels (up to four-fold) of mannose receptor. Interleukin-10 also increased, although to a lesser extent, the fluid-phase endocytosis (macropinocytosis) of fluorescein-labelled albumin. Interleukin-10 had the opposite effect on the differentiation and functional activity of monocyte-derived dendritic cells; cells having a very low stimulatory capacity and reduced expression of MHC class II and CD1a after a 7-day exposure. Thus interleukin-10 had a strong immunosuppressive effect on the differentiation and functional activity of monocyte-derived dendritic cells and yet strongly stimulated endocytosis in these cells. We speculate that an increased endocytic activity would eventually result in a decreased availability of antigens in the external milieu, thus contributing to the immunosuppressive and tolerogenic activity of interleukin-10.

Regulation of GM-CSF-induced dendritic cell development by TGF-beta1 and co-developing macrophages

Using a culture system of bone marrow progenitor cells with GM-CSF and TGF-beta1, a study was performed to analyze the effect of TGF-beta1 on the development of dendritic cells (DC) and to elucidate the regulatory role of macrophages co-developing with dendritic cells. The results demonstrate that DC generated in the presence of TGF-beta1 were immature with respect to the expression of CD86, nonspecific esterase activity and cell shape. Such inhibitory effects of TGF-beta1 were dependent on FcR+ macrophages, which were depleted by panning. TGF-beta1 did not appear to inhibit the commitment of progenitor cells to the DC lineage. In addition, TGF-beta1 also acted directly on the intermediate stage of DC to prevent their over-maturation, which results in a preferential decrease in MHC class II, but not in CD86, in the presence of TNF-alpha. FcR+ suppressive macrophages were also shown to facilitate DC maturation when stimulated via FcR-mediated signals even in the presence of TGF-beta1. These results indicate that TGF-beta1 indirectly and directly regulate the development of DC and that co-developing macrophages have a regulatory role in DC maturation.

IL-12 promotes the accessory cell function of epidermal Langerhans cells

The objective of this study was to investigate the effects of cytokines regulating cutaneous immune responses, on the accessory cell function of epidermal cells (EC). EC were treated with various cytokines, and the accessory cell function of the cytokine-pretreated EC was examined by the allogeneic mixed epidermal cell-lymphocyte reaction (MECLR). Among the cytokines examined, IFN-gamma- and IL-12-pretreated EC augmented IFN-gamma production in the MECLR, while none of the other cytokines was effective. However, the cytokine-pretreated EC did neither affect T cell proliferation nor IL-4 production in the MECLR. Next we attempted to analyze the mechanisms by which IL-12-pretreated EC increase IFN-gamma production in the MECLR. Endogenous IFN-gamma produced during the IL-12 pretreatment of EC was found to play only a minor role in modulating the function of EC. The expression of MHC class II, CD80 and CD86 on EC was not affected by IL-12. On the other hand, soluble mediators that induce IFN-gamma production during the MECLR containing IL-12-pretreated EC were identified as endogenously produced IL-12 (the major mediator) and IL-18 (the minor mediator). Furthermore, the results of depletion experiments indicate that IL-12 promotes the accessory cell function of Langerhans cells to responder T cells in inducing IFN-gamma production in the MECLR.

GM-CSF transgene expression in the airway allows aerosolized ovalbumin to induce allergic sensitization in mice

The purpose of this study was to explore whether repeated exposure to aerosolized ovalbumin (OVA) in the context of local expression of GM-CSF can initiate a Th2-driven, eosinophilic inflammation in the airways. On day -1, Balb/c mice were infected intranasally with an adenovirus construct expressing GM-CSF (Ad/GM-CSF). From day 0 to day 9 mice were exposed daily to an OVA aerosol. Mice exposed to OVA alone did not show any evidence of airway inflammation. Mice receiving both Ad/GM-CSF and aerosolized OVA exhibited marked airway inflammation characterized by eosinophilia and goblet cell hyperplasia. Migration of eosinophils into the airway was preceded by a rise in IL-5 and IL-4. Both IL-5 and class II MHC were critically required to generate airway eosinophilia. After resolution, airway eosinophilia was reconstituted after a single OVA exposure. Flow cytometric analysis of dispersed lung cells revealed an increase in macrophages and dendritic cells expressing B7.1 and B7.2, and expansion of activated (CD69-expressing) CD4 and CD8 T cells in mice exposed to OVA and Ad/GM-CSF. Our data indicate that expression of GM-CSF in the airway compartment increases local antigen presentation capacity, and concomitantly facilitates the development of an antigen-specific, eosinophilic inflammatory response to an otherwise innocuous antigen.

IL-10 and GM-CSF expression and the presence of antigen-presenting cells in chronic venous ulcers

BACKGROUND

White cell trapping and activation occurs in the legs of patients having chronic venous insufficiency (CVI), and it is thought that this process may be important in the development of CVI ulcers. This study has compared the tissue distribution of proinflammatory (GM-CSF) and anti-inflammatory cytokines (IL-10) and inflammatory cell markers (CD68, HLA-DR) between CVI ulcers, other chronic and acute wounds, and autologous nonwounded skin to determine whether cell-mediated immunity (CMI) is impaired in CVI ulcers.

METHODS

Wound and donor site tissue was obtained from 10 patients with CVI ulcers and 10 patients with other chronic and acute wounds. Serial Formalin-fixed sections were processed by standard hematoxylin and eosin staining or by indirect immunoperoxidase histochemical staining.

RESULTS

HLA-DR-positive antigen-presenting cells (APC), including CD68-positive macrophages and dermal dendritic cells, were found with greater frequency in CVI ulcers than in other chronic or acute wounds (P = 0.0015) or in the autologous CVI donor site tissue (P = 0.006). CVI ulcers also demonstrated increased IL-10 staining of the entire epidermis compared to non-CVI wounds (P = 0.0019) or autologous donor site tissue (P = 0.004), whereas there was no significant change in the presence of the counteracting cytokine, GM-CSF.

CONCLUSIONS

These findings suggest that although the cellular components of CMI are present in CVI ulcers, their function may be impaired by the increased level of IL-10. Future studies will examine whether IL-10-mediated suppression of CMI and/or inhibition of GM-CSF-stimulated keratinocyte proliferation may contribute to the chronic nature of CVI ulcers.

Down-regulation of transforming growth factor-beta and interleukin-10 secretion from malignant glioma cells by cytokines and anticancer drugs

The effect of treatment with interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma), vincristine, and etoposide was evaluated on the secretion of transforming growth factor-beta (TGF-beta) and IL-10 and the expression of major histocompatibility complex (MHC) class I, intercellular adhesion molecule-1 (ICAM-1), and CD80 molecules by malignant glioma cells. Five malignant glioma cell lines were treated with IL-1 beta, IFN-gamma, and/or anticancer agents (vincristine and etoposide). Combined treatment with IL-1 beta and IFN-gamma caused greater inhibition of TGF-beta secretion compared to treatment with IFN-gamma, and almost the same levels of inhibition as treatment with vincristine and etoposide. The greatest inhibition of TGF-beta secretion was achieved by treatment with all agents. Low levels of IL-10 secretion were determined in two out of five malignant glioma cell lines. This IL-10 secretion was inhibited by treatment with IL-1 beta, IFN-gamma, vincristine, and/or etoposide. Treatment with both cytokines and anticancer agents increased the expression of MHC class I and ICAM-1 in all tumor cell lines. The mean increase of expression of MHC class I was 50% and that of ICAM-1 was 12-fold. No tumor cell lines expressed CD80 molecules on the cell surface, and no treatment caused CD80 expression. These results suggest that TGF-beta and IL-10 secretion by malignant glioma cells can be suppressed by treatment with a combination of IL-1 beta, IFN-gamma, vincristine, and etoposide, and the treatment up-regulates MHC class I and ICAM-1 expression on tumor cells. These results have implications for immunotherapy and chemotherapy in patients with malignant tumors.

Mechanism of tolerance to class I-mismatched renal allografts in miniature swine: regulation of interleukin-2 receptor alpha-chain expression on CD8 peripheral blood lymphocytes of tolerant animals

BACKGROUND

Donor-specific tolerance to renal allografts in miniature swine is uniformly induced across a two-haplotype class I plus minor histocompatibility antigen disparity by a 12-day course of cyclosporine. Recent studies have demonstrated that the thymus is essential for rapid and stable tolerance induction, because either prior thymectomy or a series of thymic biopsies induce a spontaneously reversible rejection crisis after the 12-day course of cyclosporine. The present study examined the peripheral cellular mechanisms of tolerance by analyzing cytotoxic effector pathways in peripheral blood lymphocytes (PBL) of tolerant animals.

METHODS

The phenotype and cytotoxic T lymphocyte response of alloantigen-activated PBL cultures using cells from a series of tolerant animals with stable renal function (no thymic manipulation), or during a rejection crisis (induced by thymic biopsies), were studied. The in vitro findings were correlated with the in vivo clinical course of experimental animals.

RESULTS

The data demonstrated that in vivo and in vitro tolerance was associated with a specific deficiency of interleukin-2 receptor (IL-2R) alpha-chain up-regulation on CD8 single-positive (SP) T cells expressing high levels of CD8 (CD8high) when PBL from tolerant animals are stimulated with donor class I alloantigen. Stimulation by third party class I alloantigen, or by donor antigen during a rejection crisis, produced efficient cytotoxic T lymphocyte responses and expression of IL-2Ralpha on CD8high SP cells.

CONCLUSION

Antigen-specific regulation of the IL-2Ralpha expression on CD8high SP PBL is a principal event associated with and potentially involved in the mechanism of tolerance in this preclinical large animal model.

Requirement of CD4 cells for induction and maintenance of unresponsiveness in islet xenografted mice

Long-term survival of islet xenografts in the hamster to mouse model can be induced by a short-course treatment with a nondepleting anti-CD4 mAb but not with a depleting anti-CD4 mAb [Lu et al. Xenotransplantation 1998; 5:154-163]. Although CD4 cells are known to play a key role in the rejection of islet xenografts, it remains unclear whether CD4 cells are also required for the induction and/or maintenance of specific unresponsiveness to xenografts. To investigate this problem, islets were isolated from golden hamsters and transplanted into streptozotocin-induced diabetic CBA/J mice. Nondepleting mAb YTS 177.9 was used to block CD4 cells for the induction of islet xenograft unresponsiveness and subsequently depleting mAb GK1.5 to deplete CD4 cells in the unresponsive recipients. First, we now confirm that second donor-strain xenografts were permanently accepted in recipients that had been unresponsive to the first grafts, whereas Lewis rat islet xenografts, used as third-party grafts, were rejected like a primary graft within 7-8 days. Second, we depleted CD4 cells in recipient mice, which had been treated perioperatively with the nondepleting mAb YTS 177.9 and became unresponsive to their primary hamster islet graft, by using a depleting anti-CD4 mAb at different time points post-transplant. Depletion of CD4 cells in the unresponsive recipients by the depleting anti-CD4 mAb GK1.5 did abrogate this unresponsive state, since the grafts were always rejected within an average of 25.5 days after the mAb GK1.5 injections. Therefore, our results strongly suggest that CD4 positive cells play an active suppressive role and that their presence in the recipients appears essential for both induction and maintenance of long-term islet xenograft survival or specific unresponsiveness.

Compartmentalized transgene expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in mouse lung enhances allergic airways inflammation

To investigate the role of GM-CSF in asthmatic airways inflammation, we have targeted GM-CSF transgene to the airway cells in a mouse model of ovalbumin (OVA)-induced allergic airways inflammation, a model in which there is marked induction of endogenous IL-5 and IL-4 but not GM-CSF. Following intranasal delivery of a replication-deficient adenoviral gene transfer vector (Ad), transgene expression was found localized primarily to the respiratory epithelial cells. Intranasal delivery of 0.03 x 10(9) plaque-forming units (PFU) of AdGM-CSF into naive BALB/c mice resulted in prolonged and compartmentalized release of GM-CSF transgene protein with a peak concentration of approximately 80 pg/ml detected in bronchoalveolar lavage fluid (BALF) at day 7, but little in serum. These levels of local GM-CSF expression per se resulted in no eosinophilia and only a minimum of tissue inflammatory responses in the lung of naive mice, similar to those induced by the control vector. However, such GM-CSF expression in the airways of OVA-sensitized mice resulted in a much greater and sustained accumulation of various inflammatory cell types, most noticeably eosinophils, both in BALF and airway tissues for 15-21 days post-OVA aerosol challenge, at which times airways inflammation had largely resolved in control mice. While the levels of IL-5 and IL-4 in BALF and the rate of eosinophil apoptosis were found similar between different treatments, there was an increased number of proliferative leucocytes in the lung receiving GM-CSF gene transfer. Our results thus provide direct experimental evidence that GM-CSF can significantly contribute to the development of allergic airways inflammation through potentiating and prolonging inflammatory infiltration induced by cytokines such as IL-5 and IL-4.

Cytokine expression in squamous intraepithelial lesions of the uterine cervix: implications for the generation of local immunosuppression

We have addressed the notion that the progression of cancer of the uterine cervix is associated with a preferential constraint on the development of a type 1 cellular mediated response, which is necessary to efficiently eliminate (pre)neoplastic cells. Based on the importance of cytokines in the regulation of an appropriate immune response, we have evaluated the expression of IL-12p40, IL-10 and transforming growth factor-beta 1 (TGF-beta1). Using reverse transcriptase-polymerase chain reaction (RT-PCR), the expression of these three cytokines was evaluated in both low-grade (LG) and high-grade (HG) cervical squamous intraepithelial lesions (SIL) and in normal exocervix and transformation zone biopsies. Our results show that the average level of IL-12 increases within both the LG and HG SIL, compared with both control groups. Interestingly, the percentage of HG SIL expressing IL-12p40 was lower compared with LG SIL. In contrast, the expression of IL-10 increased in parallel with the severity of the lesion to a maximal level in HG SIL. Using immunohistochemistry, we ascertained the presence of IL-12 protein in SIL and IL-10 protein in the transformation zone and SIL biopsies. Both IL-12- and IL-10-producing cells were localized in the stroma, not within the SIL. Furthermore, in this study we also observed that the region of the cervix the most sensitive to lesion development, the transformation zone, was associated with higher average levels of the immunosuppressive cytokines IL-10 and TGF-beta1.

Antibodies to the costimulatory molecule CD86 interfere with ultraviolet radiation-induced immune suppression

Although almost all of the energy contained within the ultraviolet (UV) wavelengths of solar radiation is absorbed within the epidermis and upper layers of the dermis, UV irradiation can suppress the immune response to antigens introduced at distant, non-irradiated body sites. The production of immune modulatory cytokines, such as interleukin-10 (IL-10), by UV-irradiated keratinocytes and its effect on T helper type 1 (Th1)/Th2-cell balance are thought to play a major role in the induction of systemic immune suppression. Because it is suggested that costimulatory molecules, such as CD80 and CD86, differentially stimulate Th1 and Th2 cells we wished to investigate the role of these costimulatory molecules in the activation of immune suppression. We injected UV-irradiated mice with monoclonal antibodies to CD80 and CD86 and asked what effect, if any, this would have on UV-induced immune suppression. Anti-CD86, but not anti-CD80 or control rat IgG, blocked UV-induced immune suppression. Moreover, monoclonal anti-CD86 blocked the induction of suppressor T cells normally found in the spleens of the UV-irradiated mice. Monoclonal anti-CD86 also reversed the UV-induced impairment of systemic antigen-presenting cell function. IL-10 was detectable in the serum of UV-irradiated mice as compared with normal controls, and injecting UV-irradiated mice with anti-CD86, but not anti-CD80 or control rat IgG, blocked the secretion of IL-10 into the serum. We propose that UV exposure favours costimulation by CD86, which enhances the production of serum IL-10, thus suppressing Th1-cell-mediated immune reactions.

B7 Costimulatory Requirements of T Cells at an Inflammatory Site

The requirement for T cell costimulation at sites of infection and inflammation is unresolved. Herpes stromal keratitis (HSK) is a CD4+ T cell-regulated inflammatory response to herpes simplex virus type 1 infection of the cornea. Our findings suggest that susceptibility to HSK is determined by the microenvironment of the infected cornea. The cornea is normally devoid of Langerhans cells (LC), but these APC are present in the surrounding conjunctiva, and migrate into the cornea following infection. The costimulatory molecule B7-2 was constitutively expressed on LC in conjunctiva, but B7-1 was not detectable until 3 days postinfection. LC were the only cells in the cornea that expressed B7-1 through 7 days postinfection. B7-1 was expressed on some, but not all, migrating LC, suggesting that LC migration and B7-1 expression can be independently regulated. The early LC migration and B7-1 expression was independent of T cells, but T cells were required for the massive accumulation of B7-1+ LC in the cornea at the onset of inflammation. Local inhibition of B7-1 function within the infected cornea prevented HSK. Locally blocking B7-2 function did not reduce HSK incidence, but markedly reduce HSK severity. This is the first direct demonstration that naturally expressed B7 is required within an inflammatory site.

Inhibitory and Stimulatory Effects of IL-10 on Human CD8+ T Cells

IL-10 is a well-documented immunosuppressant that inhibits macrophage-dependent Ag presentation and CD4+ T cell proliferation in vitro. We report that IL-10 inhibits alloantigen-specific proliferative responses and induces a long lasting anergic state in human purified CD8+ T cells when added concomitantly with the Ag in the presence of APC. Moreover, the generation of allospecific cytotoxic activity is inhibited by IL-10. These effects are indirect and are mediated through inhibition of the costimulatory functions of APC. In contrast, IL-10 has no direct inhibitory effects on the proliferation of purified CD8+ T cells activated by anti-CD3 mAb and promotes the growth of activated CD8+ T cells in combination with low doses of IL-2. Taken together, these results indicate that IL-10 has differential effects on CD8+ T cells depending on their state of activation, which may explain both the enhancing and inhibitory effects observed after IL-10 treatment in different in vivo experimental models.

Maturation of dendritic cells induced by cytokines and haptens

Recently, elucidation has progressed on a crucial role played by dendritic cells (DCs) in the induction of primary antigen-specific immune reactions. Although mature DCs exhibit potent antigen presenting function, DCs are scattered in nonlymphoid organs throughout the body as immature cells that have only minimum antigen presenting function. When they are stimulated to maturate, they increase their expression of class II major histocompatibility (MHC) antigen and several co-stimulatory molecules, resulting in the augmentation of antigen presenting function. Furthermore, these maturated DCs move to the T-dependent areas of secondary lymphoid organs to sensitize naive T cells for these antigens. Therefore, it is important to understand the mechanism to induce the maturation of DCs. Recent progress in the study of DC biology depicts various factors, such as cytokines, bacterial products and haptens, which are responsible for DC maturation. In this paper, the mechanism of DC maturation induced by cytokines and chemicals is described.