Expression of the costimulatory molecule B7-H2 (inducible costimulator ligand) by human airway epithelial cells

Early Circulating Edema Factor in Inhalational Anthrax Infection: Does It Matter?

Anthrax toxins are critical virulence factors of Bacillus anthracis and Bacillus cereus strains that cause anthrax-like disease, composed of a common binding factor, the protective antigen (PA), and two enzymatic proteins, lethal factor (LF) and edema factor (EF). While PA is required for endocytosis and activity of EF and LF, several studies showed that these enzymatic factors disseminate within the body in the absence of PA after intranasal infection. In an effort to understand the impact of EF in the absence of PA, we used a fluorescent EF chimera to facilitate the study of endocytosis in different cell lines. Unexpectedly, EF was found inside cells in the absence of PA and showed a pole-dependent endocytosis. However, looking at enzymatic activity, PA was still required for EF to induce an increase in intracellular cAMP levels. Interestingly, the sequential delivery of EF and then PA rescued the rise in cAMP levels, indicating that PA and EF may functionally associate during intracellular trafficking, as well as it did at the cell surface. Our data shed new light on EF trafficking and the potential location of PA and EF association for optimal cytosolic delivery.

Unraveling the Role of Epithelial Cells in the Development of Chronic Rhinosinusitis

The pathophysiology of CRS is multifactorial and complex yet needs to be completed. Recent evidence emphasizes the crucial part played by epithelial cells in the development of CRS. The epithelial cells act as physical barriers and play crucial roles in host defense, including initiating and shaping innate and adaptive immune responses. This review aims to present a comprehensive understanding of the significance of nasal epithelial cells in CRS. New research suggests that epithelial dysfunction plays a role in developing CRS through multiple mechanisms. This refers to issues with a weakened barrier function, disrupted mucociliary clearance, and irregular immune responses. When the epithelial barrier is compromised, it can lead to the passage of pathogens and allergens, triggering inflammation in the body. Furthermore, impaired mucociliary clearance can accumulate pathogens and secretions of inflammatory mediators, promoting chronic inflammation. Epithelial cells can release cytokines and chemokines, which attract and activate immune cells. This can result in an imbalanced immune response that continues to cause inflammation. The interaction between nasal epithelial cells and various immune cells leads to the production of cytokines and chemokines, which can either increase or decrease inflammation. By comprehending the role of epithelial cells in CRS, we can enhance our understanding of the disease's pathogenesis and explore new therapeutics.

Immunomodulatory Properties of Immune Checkpoint Inhibitors-More than Boosting T-Cell Responses?

The approval of immune checkpoint inhibitors (ICI) that serve to enhance effector T-cell anti-tumor responses has strongly improved success rates in the treatment of metastatic melanoma and other tumor types. The currently approved ICI constitute monoclonal antibodies blocking cytotoxic T-lymphocyte-associated protein (CTLA)-4 and anti-programmed cell death (PD)-1. By this, the T-cell-inhibitory CTLA-4/CD80/86 and PD-1/PD-1L/2L signaling axes are inhibited. This leads to sustained effector T-cell activity and circumvents the immune evasion of tumor cells, which frequently upregulate PD-L1 expression and modulate immune checkpoint molecule expression on leukocytes. As a result, profound clinical responses are observed in 40-60% of metastatic melanoma patients. Despite the pivotal role of T effector cells for triggering anti-tumor immunity, mounting evidence indicates that ICI efficacy may also be attributable to other cell types than T effector cells. In particular, emerging research has shown that ICI also impacts innate immune cells, such as myeloid cells, natural killer cells and innate lymphoid cells, which may amplify tumoricidal functions beyond triggering T effector cells, and thus improves clinical efficacy. Effects of ICI on non-T cells may additionally explain, in part, the character and extent of adverse effects associated with treatment. Deeper knowledge of these effects is required to further develop ICI treatment in terms of responsiveness of patients to treatment, to overcome resistance to ICI and to alleviate adverse effects. In this review we give an overview into the currently known immunomodulatory effects of ICI treatment in immune cell types other than the T cell compartment.

Calcitonin Gene-Related Peptide Regulates the Potential Antigen Uptake Ability of Human Bronchial Epithelial Cells

In this study we tried to explore whether calcitonin gene-related peptide (CGRP) regulates the potential antigen uptaking ability of human bronchial epithelial cells (HBECs) and promoting the differentiation of Th1/Th2. We found that CGRP increased the uptake of fluorescein isothiocyanate labeled ovalbumin (FITC-OVA) by HBECs using fluorescence microscopy and flow cytometry analysis. MTT assay showed that T cells proliferated in a dose-dependent manner in the presence of OVA-pretreated HBECs and CGRP inhibited the proliferation of T cells. CGRP decreased secretion of IFN-γ, while it had no influence on secretion of IL-4 by ELISA. Our data suggest that CGRP enhanced HBECs antigen uptake ability and inhibits HBECs induced T cells proliferation.

Programmed cell death-1 expression correlates with disease severity and IL-5 in chronic rhinosinusitis with nasal polyps

BACKGROUND

Programmed cell death-1 (PD-1) is a negative regulator of T-cell responses. Expression of PD-1 and its ligands PD-L1 and PD-L2 in chronic rhinosinusitis with nasal polyps (CRSwNP) is poorly studied.

METHODS

Expression of PD-1, PD-L1, PD-L2, TGF-β, IL-5, and IL-10 mRNA was measured by real-time quantitative PCR on tissue homogenates of patients with CRSwNP (n = 21) and healthy controls (n = 21) and on primary epithelial cells. Disease severity was scored using the Lund-Mackay scores of maxillofacial computed tomography (CT) scans. Expression of PD-1 and PD-L1/L2 was evaluated at the cellular and tissue levels (n = 6) by flow cytometry and immunohistochemistry.

RESULTS

Programmed cell death-1 mRNA expression was increased in tissue homogenates from patients with CRSwNP compared with controls, irrespective of the atopy status. Importantly, expression of PD-1 correlated with the total CT scan scores (r = 0.5, P = 0.02). Additionally, a significant association was found between PD-1 mRNA and expression of IL-5 mRNA in control nasal tissue (r = 0.95, P < 0.0001) and in CRSwNP (r = 0.63, P = 0.002). PD-1 was expressed on different subsets of T cells and CD11b^- dendritic cells. Both PD-1 and its ligands were expressed on primary epithelial cells from control nasal tissue and nasal polyp tissue.

CONCLUSIONS

Higher PD-1 expression was found in CRSwNP than in nasal tissue from controls. This was associated with disease severity and tissue IL-5 expression but unrelated to the patients' atopy status.

Airway responses towards allergens - from the airway epithelium to T cells

The prevalence of allergic diseases such as allergic rhinitis is increasing, affecting up to 30% of the human population worldwide. Allergic sensitization arises from complex interactions between environmental exposures and genetic susceptibility, resulting in inflammatory T helper 2 (Th2) cell-derived immune responses towards environmental allergens. Emerging evidence now suggests that an epithelial dysfunction, coupled with inherent properties of environmental allergens, can be responsible for the inflammatory responses towards allergens. Several epithelial-derived cytokines, such as thymic stromal lymphopoietin (TSLP), IL-25 and IL-33, influence tissue-resident dendritic cells (DCs) as well as Th2 effector cells. Exposure to environmental allergens does not elicit Th2 inflammatory responses or any clinical symptoms in nonatopic individuals, and recent findings suggest that a nondamaged, healthy epithelium lowers the DCs' ability to induce inflammatory T-cell responses towards allergens. The purpose of this review was to summarize the current knowledge on which signals from the airway epithelium, from first contact with inhaled allergens all the way to the ensuing Th2-cell responses, influence the pathology of allergic diseases.

T cells and costimulation in cancer

Optimal T cell response is dependent not only on T cell receptor activation, but also on additional signaling from coreceptors. The main coreceptors include B7 and tumor necrosis factor family members. They exert costimulatory or coinhibitory effects, and their balance determines the fate of T cell response. In normal conditions, costimulators facilitate the development of protective immune response, whereas coinhibitors dampen inflammation to avoid organ/tissue damage from excessive immune reaction. In the tumor microenvironment, the balance is garbled: inhibitory pathways predominate, and T cell response is impaired. The importance of cosignaling in the tumor immune response has been experimentally and clinically demonstrated. New therapeutic strategies targeting T cell cosignaling, especially coinhibitory molecules, are under active experimental and clinical investigation. This review summarizes the functions of main T cell cosignaling axes and discusses their clinical application.

Differentiation of Th subsets inhibited by nonstructural proteins of respiratory syncytial virus is mediated by ubiquitination

Human respiratory syncytial virus (RSV), a major cause of severe respiratory diseases, constitutes an important risk factor for the development of subsequent asthma. However, the mechanism underlying RSV-induced asthma is poorly understood. Viral non-structural proteins NS1 and NS2 are critically required for RSV virulence; they strongly suppress IFN-mediated innate immunity of the host cells. In order to understand the effects of NS1 and NS2 on differentiation of Th subsets, we constructed lentiviral vectors of NS1 or NS2 to infect 16 HBE and analyzed the expression of HLA-DR, CD80 and CD86 and differentiation of Th1, Th2 and Th17 by Flow Cytometric Analysis and real-time PCR. The results showed that NS1 inhibited expression of HLA-DR, CD80 and CD86 and differentiation of Th1, Th2 and Th17 lymphocytes, which could be reversed by deleting elongin C binding domain. NS2 inhibited the differentiation of Th2 and Th17, which was reversed by proteasome inhibitors of PS-341. Our results indicated that NS1 inhibited the differentiation of T lymphocytes through its mono-ubiquitination to interacted proteins, while NS2 inhibited differentiation of Th2 and Th17 through ubiquitin-proteasome pathway, which may be related with the susceptibility to asthma after RSV infection.

Mechanisms of respiratory syncytial virus modulation of airway immune responses

Respiratory syncytial virus (RSV) most often causes severe respiratory disease in the very young and the elderly. Acute disease can also cause exacerbations of asthma in any age group. Recent findings provide insight into how the innate and adaptive immune systems respond to RSV infection and provide preliminary evidence that these effects vary significantly by RSV strain and host. Components of cell signaling pathways that induce inflammatory cytokine expression during the innate immune response and alter epithelial cell polarity through activating transcription factors, namely NF-κB, are now more clearly understood. New studies also reveal how RSV infection skews T helper (Th) cell differentiation away from the cell-mediated Th1 subset and towards the Th2 subset. There are also new data supporting preferential Th17 differentiation during RSV infection. In addition, effective immune system regulation of IL-10 expression and T regulatory cell (Treg) airway accumulation are essential for effective RSV clearance.

MODULATING CO-STIMULATION DURING ANTIGEN PRESENTATION TO ENHANCE CANCER IMMUNOTHERAPY

One of the key roles of the immune system is the identification of potentially dangerous pathogens or tumour cells, and raising a wide range of mechanisms to eliminate them from the organism. One of these mechanisms is activation and expansion of antigen-specific cytotoxic T cells, after recognition of antigenic peptides on the surface of antigen presenting cells such as dendritic cells (DCs). However, DCs also process and present autoantigens. Therefore, antigen presentation has to occur in the appropriate context to either trigger immune responses or establishing immunological tolerance. This is achieved by co-stimulation of T cells during antigen presentation. Co-stimulation consists on the simultaneous binding of ligand-receptor molecules at the immunological synapse which will determine the type and extent of T cell responses. In addition, the type of cytokines/chemokines present during antigen presentation will influence the polarisation of T cell responses, whether they lead to tolerance, antibody responses or cytotoxicity. In this review, we will focus on approaches manipulating co-stimulation during antigen presentation, and the role of cytokine stimulation on effective T cell responses. More specifically, we will address the experimental strategies to interfere with negative co-stimulation such as that mediated by PD-L1 (Programmed cell death 1 ligand 1)/PD-1 (Programmed death 1) to enhance anti-tumour immunity.

Downregulation of integrin β4 decreases the ability of airway epithelial cells to present antigens

Airway epithelial cells have been demonstrated to be accessory antigen presentation cells (APC) capable of activating T cells and may play an important role in the development of allergic airway inflammation of asthma. In asthmatic airways, loss of expression of the adhesion molecule integrin β4 (ITGB4) and an increase in Th2 inflammation bias has been observed in our previous study. Given that ITGB4 is engaged in multiple signaling pathways, we studied whether disruption of ITGB4-mediated cell adhesion may contribute to the adaptive immune response of epithelial cells, including their ability to present antigens, induce the activate and differentiate of T cells. We silenced ITGB4 expression in bronchial epithelial cells with an effective siRNA vector and studied the effects of ITGB4 silencing on the antigen presentation ability of airway epithelial cells. T cell proliferation and cytokine production was investigated after co-culturing with ITGB4-silenced epithelial cells. Surface expression of B7 homologs and the major histocompatibility complex (MHC) class II was also detected after ITGB4 was silenced. Our results demonstrated that silencing of ITGB4 resulted in impaired antigen presentation processes and suppressed T cell proliferation. Meanwhile, decrease in Th1 cytokine production and increase in Th17 cytokine production was induced after co-culturing with ITGB4-silenced epithelial cells. Moreover, HLA-DR was decreased and the B7 homologs expression was different after ITGB4 silencing. Overall, this study suggested that downregulation of ITGB4 expression in airway epithelial cells could impair the antigen presentation ability of these cells, which further regulate airway inflammation reaction in allergic asthma.

Activation of lymphocytes induced by bronchial epithelial cells with prolonged RSV infection

Respiratory syncytial virus (RSV) preferentially infects airway epithelial cells,which might be responsible for susceptibility to asthma; however, the underlying mechanism is not clear. This study determined the activation of lymphocytes and drift of helper T (Th) subsets induced by RSV-infected human bronchial epithelial cells (HBECs) in vitro. HBECs had prolonged infection with RSV, and lymphocytes isolated from human peripheral blood were co-cultured with RSV-infected HBECs. Four groups were established, as follows: lymphocytes (group L); lymphocytes infected with RSV (group RL); co-culture of lymphocytes with non-infected HBECs (group HL); and co-culture of lymphocytes with infected HBECs (group HRL). After co-culture with HBECs for 24 hours, lymphocytes were collected and the following were determined in the 4 groups: cell cycle status; apoptosis rate; and concentrations of IL-4, IFN-γ, and IL-17 in the supernatants. Cell cycle analysis for lymphocytes showed a significant increase in S phase cells, a decrease in G1 phase cells, and a higher apoptosis rate in group HRL compared with the other three groups. In group HRL, the levels of IL-4, IFN-γ, and IL-17 in supernatants were also higher than the other three groups. For further study, lymphocytes were individually treated with supernatants from non-infected and RSV-infected HBECs for 24 h. We showed that supernatants from RSV-infected HBECs induced the differentiation of Th2 and Th17 subsets, and suppressed the differentiation of Treg subsets. Our results showed that HBECs with prolonged RSV infection can induce lymphocyte proliferation and apoptosis, and enhance the release of cytokines by lymphocytes. Moreover, subset drift might be caused by RSV-infected HBECs.

Expression and function of the inducible costimulator ligand B7-H2 in human airway smooth muscle cells

BACKGROUND

B7-H2 is a ligand for the inducible costimulator (ICOS). The aim of this study was to examine the expression and function of B7-H2 in human airway smooth muscle (ASM) cells and compare them with those of CD40 or OX40 ligand (OX40L).

METHODS

Expression of B7-H2, CD40 and OX40L in ASM cells and their respective counterparts in T cells was analyzed by RT-PCR or flow cytometry. The modulating effect of polyinosinic-polycytidylic acid (poly I:C) on expression of B7-H2, CD40 and OX40L was also examined. The function of these three molecules was evaluated by virtue of adhesion of anti-CD3-activated T cells, IL-6 and IL-8 production and DNA synthesis.

RESULTS

ASM cells constitutively expressed B7-H2, CD40 and OX40L that mediated adhesion of activated T cells expressing ICOS, CD40L and OX40. ASM cells responded to poly I:C with upregulated expression of B7-H2, CD40 and OX40L and displayed enhanced adhesion of activated T cells. Functional analysis performed on untreated ASM cells showed that engagement of B7-H2 with ICOS-Ig clearly induced DNA synthesis, whereas that of CD40 or OX40L with trimeric CD40L or OX40-Ig greatly increased IL-6 and IL-8 production. These responses were enhanced in poly I:C-treated ASM cells.

CONCLUSIONS

The data demonstrate that ASM cells express functionally active B7-H2, CD40 and OX40L and suggest that B7-H2-dependent signaling may play an active role in a proliferative response rather than in cytokine and chemokine production. In addition, the modulation of B7-H2, CD40 and OX40L expression and function by poly I:C may have important implications for the function of virus-infected ASM cells.

Epithelium, inflammation, and immunity in the upper airways of humans: studies in chronic rhinosinusitis

The purpose of this review is to discuss recent findings made during studies of the upper airways and sinuses of people with chronic rhinosinusitis (CRS) in the context of the literature. CRS is a chronic inflammatory disorder affecting nearly 30 million Americans and is generally resistant to therapy with antibiotics and glucocorticoids (Meltzer EO and coworkers, J Allergy Clin Immunol 2004;114:155-212). We have formed a collaboration that consists of otolaryngologists, allergists, and basic scientists to address the underlying immunologic and inflammatory processes that are occurring in, and possibly responsible for, this disease. The main emphasis of our work has been to focus on the roles that epithelium, in the sinuses and upper airways, plays as both a mediator and regulator of immune and inflammatory responses. It is not our intention here to provide a comprehensive review of the literature in this area, but we will try to put our work in the context of the findings of others (Kato A and Schleimer RP, Curr Opin Immunol 2007;19:711-720; Schleimer RP and coworkers, J Allergy Clin Immunol 2007;120:1279-1284). In particular, we discuss the evidence that epithelial cell responses are altered in CRS, including those relevant to regulation of dendritic cells, T cells, B cells, and barrier function.

Induction of B7-H1 and B7-DC expression on airway epithelial cells by the Toll-like receptor 3 agonist double-stranded RNA and human rhinovirus infection: In vivo and in vitro studies

BACKGROUND

T-cell infiltration of the epithelium is a key feature of chronic rhinosinusitis and asthma. Viral infections are an important cause of disease exacerbations. We have found virus-induced expression of T cell-interacting ligands, B7 homolog costimulatory molecules, on airway epithelium.

OBJECTIVE

We tested the ability of human rhinovirus (HRV) 16 and double-stranded RNA (dsRNA) to alter the expression of B7 homologs on human airway epithelial cells.

METHODS

BEAS2B and primary human airway epithelial cells were exposed in vitro to dsRNA (25 microg/mL) or HRV-16, and then expression of cell-surface protein and mRNA for B7 homologs was assessed by means of flow cytometry and real-time PCR, respectively. Additionally, human subjects were infected with HRV-16 in vivo, and mRNA for B7 homologs was assessed by means of real-time PCR in fresh nasal epithelial cell scrapings obtained before and daily up to 4 days after infection.

RESULTS

dsRNA exposure of BEAS2B and human primary bronchial epithelial cells resulted in increased levels of cell-surface and mRNA expression of B7-H1 and B7-DC but not B7-H2 or B7-H3. Exposure of primary cells to HRV-16 resulted in induction of cell-surface expression of B7-H1 and B7-DC. Pretreatment with fluticasone propionate failed to suppress the induction of B7-H1 and B7-DC. Nasal scrapings taken at the time of peak symptom scores (3 days) after infection of 6 human subjects with HRV-16 displayed selective induction of levels of mRNA for B7-H1 and B7-DC.

CONCLUSION

These data show that HRV-16 infection or exposure to dsRNA induces epithelial B7-H1 and B7-DC.

Epithelium: at the interface of innate and adaptive immune responses

Several diseases of the airways have a strong component of allergic inflammation in their cause, including allergic rhinitis, asthma, polypoid chronic rhinosinusitis, eosinophilic bronchitis, and others. Although the roles played by antigens and pathogens vary, these diseases have in common a pathology that includes marked activation of epithelial cells in the upper airways, the lower airways, or both. Substantial new evidence indicates an important role of epithelial cells as both mediators and regulators of innate immune responses and adaptive immune responses, as well as the transition from innate immunity to adaptive immunity. The purpose of this review is to discuss recent studies that bear on the molecular and cellular mechanisms by which epithelial cells help to shape the responses of dendritic cells, T cells, and B cells and inflammatory cell recruitment in the context of human disease. Evidence will be discussed that suggests that secreted products of epithelial cells and molecules expressed on their cell surfaces can profoundly influence both immunity and inflammation in the airways.

Role of human neutrophil peptides in the initial interaction between lung epithelial cells and CD4+ lymphocytes

Human neutrophil peptides (HNP) exert immune-modulating effects. We hypothesized that HNP link innate and adaptive immunity through activation of costimulatory molecules. Human lung epithelial cells and CD4+ lymphocytes were treated with HNP separately or in coculture. Stimulation with HNP induced an increase in cell surface expression of CD54 (ICAM-1), CD80, and CD86 on lung epithelial cells and the corresponding major ligands, CD11a (LFA-1), CD152 (CTLA-4), and CD28 on CD4+ lymphocytes. There was an increased nuclear expression of the transcription factor p53 in human alveolar A549 cells and an elevated NF-kappaB (p50) and a degradation of I-kappaB protein in CD4+ lymphocytes following HNP stimulation. HNP enhanced the interaction between A549 cells and CD4+ lymphocytes by increasing cell adhesion and release of IFN-gamma, IL-2, and IL-8. This was attenuated by using an alpha1-proteinase inhibitor to neutralize HNP. We conclude that HNP play an important role in linking innate to acquired immunity by activation of costimulatory molecules in lung epithelial cells and CD4+ lymphocytes.

Functional analysis of the chemokine receptor CCR3 on airway epithelial cells

The function of chemokine receptors on structural cells is only partially known. We previously reported the expression of a functional CCR3 receptor on airway epithelial cells (EC). We speculated that CCR3 might drive wound repair and expression of inflammatory genes in epithelium. The human airway EC lines BEAS-2B, 16-HBE, and primary bronchial EC were used to test the effect of in vitro challenge with the CCR3 ligands CCL11/eotaxin, CCL24/eotaxin-2, or CCL26/eotaxin-3 on 1) wound repair, using an established wound model; 2) cell proliferation and chemotaxis, using specific fluorometric assays; and 3) gene expression, using pathway-specific arrays for inflammatory and profibrotic cytokines, chemokines, and chemokine receptor genes. Agonist specificity was tested by cell pretreatment with an AstraZeneca CCR3 antagonist (10(-8) - 10(-6) M). CCL24 challenge significantly accelerated epithelial wound closure, with similar effects exerted by CCL11 and CCL26. This effect was time dependent, submaximal at 1 nM, and comparable in potency to epidermal growth factor. CCL24 induced a concentration-dependent increase in EC proliferation and chemotaxis, with significant effects observed at 10 nM. The AstraZeneca compound selectively inhibited these CCL24-mediated responses. CCL11 induced the up-regulation of several profibrogenic molecules such as fibroblast growth factor 1 and 5 and of several CC and CXC chemokines. Epithelial immunostaining for CCR3 was stronger in bronchial biopsies of asthmatics displaying marked inflammatory changes than in nondiseased samples. Epithelial CCR3 participates in key functions for wound repair, amplifies the expression of profibrogenic and chemokine transcripts, and appears up-regulated in inflamed asthmatic airways.

The ICOS-ligand B7-H2, expressed on human type II alveolar epithelial cells, plays a role in the pulmonary host defense system

The mechanism of immune defense against pathogens in the lung, has so far been poorly understood. Here, we show that human type II alveolar epithelial cells play a key role in defense via interactions between B7 homolog (B7h), also known as ICOS ligand, and its receptor ICOS expressed on activated T cells. The A549 alveolar type II cell line abundantly expresses B7-H2, CD40 and B7-1, but not B7-2 or hGL50. TNF-alpha significantly induced B7-H2 and CD40 expression by A549 cells, but had no effect on B7-1 or B7-2 expression. TNF-alpha-deficient mice exhibited low B7-H2 expression on alveolar epithelial cells in comparison with wild-type mice. Co-culture of TNF-alpha pre-stimulated A549 cells with CD4+ T cells promoted CD154 expression, CD4+ T cell proliferation and cytokine production, especially IFN-gamma. Monocyte-derived TNF-alpha in combination with IFN-gamma and LPS markedly induced B7-H2 expression in A549 cells. This study thus identifies a unique costimulatory pathway via alveolar epithelial type II cells that preferentially affects T helper cell function, implying that alveolar epithelial type II cells play a crucial role in innate immunity in the lung by regulating IFN-gamma-synthesis via B7-H2/ICOS interactions.

Effect of tolerance induction to immunodominant T-cell epitopes of Sendai virus on gene expression following repeat administration to lung

Sendai virus (SeV) is able to transfect airway epithelial cells efficiently in vivo. However, as with other viral vectors, repeated administration leads to reduced gene expression. We have investigated the impact of inducing immunological tolerance to immunodominant T-cell epitopes on gene expression following repeated administration. Immunodominant CD4 and CD8 T-cell peptide epitopes of SeV were administered to C57BL/6 mice intranasally 10 days before the first virus administration with transmission-incompetent F-protein-deleted DeltaF/SeV-GFP. At 21 days after the first virus administration, mice were again transfected with DeltaF/SeV. To avoid interference of anti-GFP antibodies, the second transfection was carried out with DeltaF/SeV-lacZ. At 2 days after the final transfection lung beta-galactosidase expression, T-cell proliferation and antibody responses were measured. A state of 'split tolerance' was achieved with reduced T-cell proliferation, but no impact on antiviral antibody production. There was no enhancement of expression on repeat administration; instead, T-cell tolerance was, paradoxically, associated with a more profound extinction of viral expression. Multiple immune mechanisms operate to eradicate viruses from the lung, and these findings indicate that impeding the adaptive T-cell response to the immunodominant viral epitope is not sufficient to prevent the process.

Constitutive and inducible expression of b7 family of ligands by human airway epithelial cells

Activated T cells have been implicated in chronic rhinosinusitis (CRS) and asthma and physically interact with epithelial cells in the airways. We now report that human airway epithelial cells display significant constitutive cell-surface expression of costimulatory ligands, B7-H1, B7-H2, B7-H3, and B7-DC. Expression of B7-H1 and B7-DC was selectively induced by stimulation of either BEAS2B or primary nasal epithelial cells (PNEC) with interferon (IFN)-gamma (100 ng/ml). The combination of IFN-gamma and tumor necrosis factor-alpha (100 ng/ml) selectively induced expression better than IFN-gamma alone. Fluticasone treatment (10(-7) M) reduced the baseline expression and inhibited the induction of B7-H1 and B7-DC in BEAS2B cells. In vitro exposure of PNEC to IFN-gamma also resulted in selective induction of B7-H1 and B7-DC. Monoclonal antibody blockade of B7-H1 or B7-DC enhanced IFN-gamma expression by purified T cells in co-culture experiments, suggesting that these two B7 homologs inhibit T cell responses at the mucosal surface. Immunohistochemical staining of human sinonasal surgical tissue confirmed the presence of B7-H1, B7-H2, and B7-H3 in the epithelial cell layer, especially in samples from patients diagnosed with Samter's Triad, a severe form of CRS. Real-time PCR analysis of sinonasal tissue revealed elevated levels of B7-H1 and B7-DC in CRS compared with controls. These results demonstrate that epithelial cells express functional B7 costimulatory molecules and that expression of selected B7 family members is inducible in vitro and in vivo. Epithelial B7 homologs could play a role in regulation of lymphocytic activity at mucosal surfaces.

Keratinocytes in atopic dermatitis: inflammatory signals

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that usually predates the development of allergic airway disease. In most cases, this is thought to be an allergen-driven disease with prominent roles played by antigen presenting cells and effector Th2 cells. But keratinocytes, by virtue of their location, provide an important window to the environment and are also thought to contribute to the development of AD. In this review, we discuss several biologic attributes of keratinocytes that are relevant for AD: 1) intrinsic defects in barrier function, 2) production of inflammatory mediators that promote or maintain allergic inflammation, 3) keratinocyte apoptosis, 4) effects of staphylococcal toxins on keratinocytes, and 5) potential consequences of the expression of cosignaling molecules (eg, B7 family members) and receptors important for innate immune responses (eg, Toll receptors). Clearly, these findings have highlighted a more active role played by the epithelium than was previously recognized.

NF-kappa B activation in airways modulates allergic inflammation but not hyperresponsiveness

Airways display robust NF-kappaB activation and represent targets for anti-inflammatory asthma therapies, but the functional importance of NF-kappaB activation in airway epithelium remains enigmatic. Therefore, transgenic mice were created in which NF-kappaB activation is repressed specifically in airways (CC10-IkappaBalpha(SR) mice). In response to inhaled Ag, transgenic mice demonstrated significantly ameliorated inflammation, reduced levels of chemokines, T cell cytokines, mucus cell metaplasia, and circulating IgE compared with littermate controls. Despite these findings, Ag-driven airways hyperresponsiveness was not attenuated in CC10-IkappaBalpha(SR) mice. This study clearly demonstrates that airway epithelial NF-kappaB activation orchestrates Ag-induced inflammation and subsequent adaptive immune responses, but does not contribute to airways hyperresponsiveness, the cardinal feature that underlies asthma.

mRNA for genes associated with antigen presentation are expressed by human middle meatal epithelial cells in culture

OBJECTIVES/HYPOTHESIS

Although the mechanisms underlying the initiation and maintenance of inflammation in chronic rhinosinusitis are poorly understood, the activation of memory T cells within the nasal mucosa is thought to play an important role. T-cell activation requires specialized antigen processing and presentation of antigen by immunocompetent cells in the context of cell surface immune molecules. The purpose of this study was to investigate the expression of such molecules by human sinonasal epithelial cells grown in culture at the air-liquid interface (ALI).

METHODS

Middle meatal epithelium was obtained from six patients undergoing endoscopic sinus surgery. Dissociated epithelial cells were grown to confluence in serum-free, defined medium and transferred to filter inserts for culture at the ALI. Cells were harvested at 2 and 21 days of growth at the ALI and processed for real-time polymerase chain reaction (PCR). The presence and relative abundance of constitutively expressed mRNA for human leukocyte antigen (HLA)-B, HLA-DR, B7 to 1, B7 to 2, B7-H2, B7-H3, and cathepsin D were assessed.

RESULTS

After 2 days at the ALI, middle meatal epithelial cells demonstrated expression of genes for each of the antigen processing associated genes tested. The expression of HLA-B and HLA-DR increased significantly with cellular maturation at the ALI. Expression of HLA-DR and B7 to 1 increased with cytokine stimulation.

CONCLUSIONS

Primary human epithelial cells obtained from the middle meatus express genes associated with antigen presentation function. The pattern of gene expression is modulated by cytokine stimulation and changes as the cells differentiate at the ALI. These findings suggest that mature middle meatal epithelial cells have the cellular machinery to interact with T cells and therefore may be direct participants in the modulation of T-cell activity in chronic sinusitis.

Accessory cell function of airway epithelial cells

Oei, Erwin, Thomas Kalb, Prarthana Beuria, Matthieu Allez, Atsushi Nakazawa, Miyuki Azuma, Michael Timony, Zanetta Stuart, Houchu Chen, and Kirk Sperber. Accessory cell function of airway epithelial cells.

We previously demonstrated that airway epithelial cells (AECs) have many features of accessory cells, including expression of class II molecules CD80 and CD86 and functional Fcγ receptors. We have extended these studies to show that freshly isolated AECs have mRNA for cathepsins S, V, and H [proteases important in antigen (Ag) presentation], invariant chain, human leukocyte antigen (HLA)-DM-α and HLA-DM-β, and CLIP, an invariant chain breakdown product. A physiologically relevant Ag, ragweed, was colocalized with HLA-DR in AECs, and its uptake was increased by granulocyte-macrophage colony-stimulating factor and IFN-γ treatments, which had no effect on CD80 and CD86 expression. We demonstrate the presence of other costimulatory molecules, including B7h and B7-H1, on AECs and the increased expression of B7-H1 on AECs after treatment with granulocyte-macrophage colony-stimulating factor and IFN-γ. Finally, we compared T cell proliferation after allostimulation with AECs and dendritic cells (DCs). The precursor frequency of peripheral blood T cells responding to AECs was 0.264% compared with 0.55% for DCs. DCs stimulated CD45RO+, CD45RA+, CCR7+and CCR7−CD4+, and CD8+T cells, whereas AECs stimulated only CD45RO+, CD45RA−, CCR7−, CD4+, and CD8+T cells. There was no difference in cytokine production, type of memory T cells stimulated (effector vs. long-term memory), or apoptosis by T cells cocultured with AECs and DCs. The localization of AECs exposed to the external environment may make them important in the regulation of local immune responses.

Expression of genes for B7-H3 and other T cell ligands by nasal epithelial cells during differentiation and activation

Epithelial cells of the human respiratory tract express human leukocyte antigen (HLA) and the costimulatory molecules B7-1 and B7-2. Little is known, however, about the constitutive expression of genes encoding for the more recently identified members of the B7 homolog family of costimulatory molecules or about the influence of cellular differentiation and cytokines on their activity or on that of HLA or B7-1 and B7-2. Human nasal epithelial (HNE) cells were grown at the air-liquid interface (ALI) for 2 or 21 days to model in vivo conditions. Expression of genes for HLA-B and HLA-DR1 increased during mucociliary differentiation during this period and became more similar to HNE cells obtained fresh by brush biopsy from nasal turbinates. Gene transcripts for B7-H3 and B7-H2 were abundantly expressed in cells cultured at the ALI, but neither their activities nor that of B7-2 was significantly altered during differentiation. IFN-gamma and TNF-alpha upregulated mRNA encoding for both HLA molecules, but not for the B7 molecules. This study describes, for the first time, the expression of B7-H3 and B7-H2 by HNE cells and thus expands the range of potential costimulatory signals through which these cells may interact with activated mucosal T lymphocytes. In addition, the results suggest that the extent of mucociliary differentiation of cultured cells may influence this capability.