Induction of Fas ligand-mediated apoptosis by interferon-alpha

Type I interferon and cancer

Type I interferon (IFN) is a class of proinflammatory cytokines with a dual role on malignant transformation, tumor progression, and response to therapy. On the one hand, robust, acute, and resolving type I IFN responses have been shown to mediate prominent anticancer effects, reflecting not only their direct cytostatic/cytotoxic activity on (at least some) malignant cells, but also their pronounced immunostimulatory functions. In line with this notion, type I IFN signaling has been implicated in the antineoplastic effects of various immunogenic therapeutics, including (but not limited to) immunogenic cell death (ICD)-inducing agents and immune checkpoint inhibitors (ICIs). On the other hand, weak, indolent, and non-resolving type I IFN responses have been demonstrated to support tumor progression and resistance to therapy, reflecting the ability of suboptimal type I IFN signaling to mediate cytoprotective activity, promote stemness, favor tolerance to chromosomal instability, and facilitate the establishment of an immunologically exhausted tumor microenvironment. Here, we review fundamental aspects of type I IFN signaling and their context-dependent impact on malignant transformation, tumor progression, and response to therapy.

Toll-like Receptors from the Perspective of Cancer Treatment

Toll-like receptors (TLRs) represent a family of pattern recognition receptors that recognize certain pathogen-associated molecular patterns and damage-associated molecular patterns. TLRs are highly interesting to researchers including immunologists because of the involvement in various diseases including cancers, allergies, autoimmunity, infections, and inflammation. After ligand engagement, TLRs trigger multiple signaling pathways involving nuclear factor-κB (NF-κB), interferon-regulatory factors (IRFs), and mitogen-activated protein kinases (MAPKs) for the production of various cytokines that play an important role in diseases like cancer. TLR activation in immune as well as cancer cells may prevent the formation and growth of a tumor. Nonetheless, under certain conditions, either hyperactivation or hypoactivation of TLRs supports the survival and metastasis of a tumor. Therefore, the design of TLR-targeting agonists as well as antagonists is a promising immunotherapeutic approach to cancer. In this review, we mainly describe TLRs, their involvement in cancer, and their promising properties for anticancer drug discovery.

A novel management proposal for intrinsic brainstem neurenteric cysts: case report

Neurenteric cysts (NCs) are rare congenital lesions with epithelial mucin-secreting walls. They can occur anywhere along the neural axis, and an intrinsic midbrain cyst is extraordinary. Surgical management may pose a challenge due to the location of the lesion and adhesion of the cyst wall to the surrounding brainstem. The authors describe the first case of pediatric NC that was treated successfully with intracystic interferon-α (IFN-α).A 16-month-old baby girl presented with a 2-week history of progressive croup, vomiting, and swallowing difficulty. MRI revealed a 1.8-cm cystic intrinsic lesion in the pontomedullary region. She initially underwent posterior fossa craniotomy and drainage of the cyst under intraoperative neurophysiology monitoring. Three weeks following the procedure, her symptoms recurred, and follow-up MRI demonstrated cystic recurrence. She underwent repeat aspiration of the cyst and biopsy of the cyst wall, and INF-α-2b was injected into the cystic cavity. Her symptoms improved and completely resolved after 5 months. A 9-month follow-up brain MRI study showed complete resolution of the NC. Intracystic IFN-α injection after cystic content aspiration may be a safe treatment option for the management of intrinsic brainstem NCs. Long-term clinical and radiological follow-up is recommended.

TREX1 variants in Sjogren's syndrome related lymphomagenesis

Genetic variants of the three-prime repair exonuclease 1 (TREX1) -an exonuclease involved in DNA repair and degradation- have been previously found to increase susceptibility to Aicardi Goutieres syndrome, familial chilblain lupus and systemic lupus erythematosus. We aimed to explore whether TREX1 common variants could influence the risk of primary Sjogren's syndrome (SS) and SS-related lymphoma. Three single nucleotide polymorphisms (SNPs) of the TREX1 gene (rs11797, rs3135941 and rs3135945) were evaluated in 229 SS, 89 SS-lymphoma (70 SS-MALT and 19 SS non-MALT) and 240 healthy controls by PCR-based assays. In available 52 peripheral blood and 26 minor salivary gland tissues from our SS cohort, mRNA expression of type I interferon (IFN) related genes and TREX1 was determined by real-time PCR. Significantly decreased prevalence of rs11797 A minor allele was detected in SS patients complicated by non-MALT lymphoma compared to controls (ΟR [95% CI]: 0.4 [0.2-0.9], p-value: 0.02). SS patients carrying the rs11797 AA genotype had increased type I IFN related gene mRNA expression in minor salivary gland tissues. These data support genetically related dampened type I IFN production as an additional mechanism for SS-related lymphomagenesis.

Global virus outbreaks: Interferons as 1st responders

Outbreaks of severe virus infections with the potential to cause global pandemics are increasing. In many instances these outbreaks have been newly emerging (SARS coronavirus), re-emerging (Ebola virus, Zika virus) or zoonotic (avian influenza H5N1) virus infections. In the absence of a targeted vaccine or a pathogen-specific antiviral, broad-spectrum antivirals would function to limit virus spread. Given the direct antiviral effects of type I interferons (IFNs) in inhibiting the replication of both DNA and RNA viruses at different stages of their replicative cycles, and the effects of type I IFNs on activating immune cell populations to clear virus infections, IFNs-α/β present as ideal candidate broad-spectrum antivirals.

Characterization, functional and signaling elucidation of pigeon (Columba livia) interferon-α: Knockdown p53 negatively modulates antiviral response

The regulation of interferon-α signaling pathways is essential to protect the host from infection with a broad range of viruses. However, information regarding antiviral response and the specific molecular mechanism of Columba livia interferon-α (CoIFN-α) has not been reported to date. In this study, we cloned a 723bp complete ORF of CoIFN-α gene. The specific antiviral activity of CoIFN-α in VSV (TCID₅₀ = 10^-5.87/100 μL)-infected CEFs reached 5.5 × 10⁵ U/mg. Moreover, our result indicated that the anti-VSV efficient of CoIFN-α might depend on the expression of NF-κB. CoIFN-α also showed high sensitivity to trypsin and relatively stable after acid, alkali or heat treatment. Moreover, CoIFN-α activated STAT/Jak signaling and autophagy to inhibit VSV-induced apoptosis. Although the expression of p53 was further increased, apoptosis was not involved in CoIFN-α against VSV. Notably, although STAT signaling was efficiently activated, knockdown p53 did inhibit the antiviral activity of the CoIFN-α via decreasing the expression of Mx1 but not weakened Jak phosphorylation. Moreover, VSV aggravated the apoptosis and the expression of cleaved Mdm2 in knockdown p53 under preincubated CoIFN-α. Taken together, p53 might as a highly interconnected regulator in IFN-α antiviral response and cleaved Mdm2 might as a dominant-negative regulator by competing with full length Mdm2 for p53 binding in virus infection. Overall, our research not only enriches CoIFN-α antiviral features but also helps explain that p53 enhance the CoIFN-α antiviral response against pigeon viral diseases.

Hyaluronic Acid Microgels Modulate Inflammation and Key Matrix Molecules toward a Regenerative Signature in the Injured Annulus Fibrosus

Low back pain results from disc degeneration, which is a chronic inflammatory disease characterized by an imbalance between anabolic and catabolic factors. Today, regenerative medicine is focused on identifying inflammatory markers to target disc disease. Hyaluronan is used as a scaffold for cell delivery in disc degeneration; however, to date high molecular weight hyaluronan (HMW HA) is evaluated for its anti-inflammatory and matrix modulatory properties in an in vivo disc injury model. Ex vivo bovine organ culture studies demonstrate the anti-inflammatory and matrix modulatory effects of HMW HA on the IFNα2β signaling pathway that provides the motivation for evaluating its efficacy in regenerating the annulus fibrosus in an in vivo disc injury model. It is demonstrated that the HMW HA microgel acts as an anti-inflammatory molecule in the annulus fibrosus, by downregulating the expression of the pro-inflammatory interferon gamma (IFNα) and pro-apoptotic insulin-like growth factor-binding protein 3 (IGFBP3) and the apoptosis marker caspase 3. Mass spectrometry studies demonstrate that the HMW HA microgel modulates the matrix modulatory effect by upregulating hyaluronic acid link protein (HAPLN1) and aggrecan, which are further confirmed by immunostaining. The microgel's regenerative capacity is illustrated by the increase in the disc height index.

Balance between IL-3 and type Iinterferons and their interrelationship with FasL dictates lifespan and effector functions of human basophils

BACKGROUND

In contrast to eosinophils and neutrophils, the regulation of the lifespan of human basophils is poorly defined, with the exception of the potent anti-apoptotic effect of IL-3 that also promotes pro-inflammatory effector functions and phenotypic changes. Type I IFNs (IFN-α, IFN-β), which are well known for their anti-viral activities, have the capacity to inhibit allergic inflammation.

OBJECTIVE

To elucidate whether type I IFNs have the potential to abrogate the lifespan and/or effector functions of human basophils.

METHODS

We cultured human basophils, and for comparison, eosinophils and neutrophils, with IL-3, interferons, FasL and TRAIL, alone or in combination, and studied cell survival, effector functions and signalling pathways involved.

RESULTS

Despite an identical pattern of early signalling in basophils, eosinophils and neutrophils in response to different types of interferons, only basophils displayed enhanced apoptosis after type I IFN treatment. IFN-γ prolonged survival of eosinophils but did not affect the lifespan of basophils. IFN-α-mediated apoptosis required STAT1-STAT2 heterodimers and the contribution of constitutive p38 MAPK activity. Whereas the death ligands FasL and TRAIL-induced apoptosis in basophils per se, IFN-α-mediated apoptosis did neither involve autocrine TRAIL signalling nor did it sensitize basophils to FasL-induced apoptosis. However, IFN-α and FasL displayed an additive effect in killing basophils. Interestingly, IL-3, which protected basophils from IFN-α-, TRAIL- or FasL-mediated apoptosis, did not completely block the additive effect of combined IFN-α and FasL treatment. Moreover, we demonstrate that IFN-α suppressed IL-3-induced release of IL-8 and IL-13. In contrast to IFN-α-mediated apoptosis, these inhibitory effects of IFN-α were not dependent on p38 MAPK signalling.

CONCLUSIONS AND CLINICAL RELEVANCE

Our study defines the unique and granulocyte-type-specific inhibitory and pro-apoptotic function of type I IFNs and their cooperation with death ligands in human blood basophils, which may be relevant for the anti-allergic properties of type I IFNs.

Type I and II interferon signatures in Sjogren's syndrome pathogenesis: Contributions in distinct clinical phenotypes and Sjogren's related lymphomagenesis

Both type I and II interferons (IFNs) have been implicated in the pathogenesis of Sjogren's syndrome (SS). We aimed to explore the contribution of type I and II IFN signatures in the generation of distinct SS clinical phenotypes including lymphoma development. Peripheral blood (PB) from SS patients (n = 31), SS patients complicated by lymphoma (n = 13) and healthy controls (HC, n = 30) were subjected to real-time PCR for 3 interferon inducible genes (IFIGs) preferentially induced by type I IFN, 2 IFIGs preferentially induced by IFNγ as well as for IFNα and IFNγ genes. The same analysis was performed in minor salivary gland tissues (MSG) derived from 31 SS patients, 10 SS-lymphoma patients and 17 sicca controls (SC). In PB and MSG tissues, overexpression of both type I and type II IFIGs was observed in SS patients versus HC and SC, respectively, with a predominance of type I IFN signature in PB and a type II IFN signature in MSG tissues. In SS-lymphoma MSG tissues, lower IFNα, but higher IFNγ and type II IFIG transcripts compared to both SS and SC were observed. In receiver operating characteristic curve analysis, IFNγ/IFNα mRNA ratio in MSG tissues showed the best discrimination for lymphoma development. Discrete expression patterns of type I and II IFN signatures might be related to distinct SS clinical phenotypes. Additionally, IFNγ/IFNα mRNA ratio in diagnostic salivary gland biopsies is proposed as a novel histopathological biomarker for the prediction of in situ lymphoma development in the setting of SS.

Bioinformatics analysis of the factors controlling type I IFN gene expression in autoimmune disease and virus-induced immunity

Patients with systemic lupus erythematosus (SLE) and Sjögren’s syndrome (SS) display increased levels of type I interferon (IFN)-induced genes. Plasmacytoid dendritic cells (PDCs) are natural interferon producing cells and considered to be a primary source of IFN-α in these two diseases. Differential expression patterns of type I IFN-inducible transcripts can be found in different immune cell subsets and in patients with both active and inactive autoimmune disease. A type I IFN gene signature generally consists of three groups of IFN-induced genes – those regulated in response to virus-induced type I IFN, those regulated by the IFN-induced mitogen-activated protein kinase/extracellular-regulated kinase (MAPK/ERK) pathway, and those by the IFN-induced phosphoinositide-3 kinase (PI-3K) pathway. These three groups of type I IFN-regulated genes control important cellular processes such as apoptosis, survival, adhesion, and chemotaxis, that when dysregulated, contribute to autoimmunity. With the recent generation of large datasets in the public domain from next-generation sequencing and DNA microarray experiments, one can perform detailed analyses of cell-type specific gene signatures as well as identify distinct transcription factors (TFs) that differentially regulate these gene signatures. We have performed bioinformatics analysis of data in the public domain and experimental data from our lab to gain insight into the regulation of type I IFN gene expression. We have found that the genetic landscape of the IFNA and IFNB genes are occupied by TFs, such as insulators CTCF and cohesin, that negatively regulate transcription, as well as interferon regulatory factor (IRF)5 and IRF7, that positively and distinctly regulate IFNA subtypes. A detailed understanding of the factors controlling type I IFN gene transcription will significantly aid in the identification and development of new therapeutic strategies targeting the IFN pathway in autoimmune disease.

Anti-interferon alpha treatment in SLE

Several studies in the last decade have highlighted the role of the type I interferon (IFN-I) pathway, and particularly interferon alpha (IFNα) in SLE pathogenesis. As a result, a multitude of potential treatments targeting IFNα have emerged in the last few years, a few of which have already completed phase II clinical trials. Some of the treatment strategies have focused on blocking IFNα or its receptor and others the plasmacytoid dendritic cell (pDC), which is the principal IFNα producing cell. In this review, we will discuss the evidence supporting a pathogenic role of IFNα and pDC in SLE, provide an update on the current status of these therapeutic strategies, and discuss the potential advantages and disadvantages of each therapeutic approach.

Interferon-induced TRAIL-independent cell death in DNase II-/- embryos

The chromosomal DNA of apoptotic cells and the nuclear DNA expelled from erythroid precursors is cleaved by DNase II in lysosomes after the cells or nuclei are engulfed by macrophages. DNase II(-/-) embryos suffer from lethal anemia due to IFN-beta produced in the macrophages carrying undigested DNA. Here, we show that Type I IFN induced a caspase-dependent cell death in human epithelial cells that were transformed to express a high level of IFN type I receptor. During this death process, a set of genes was strongly activated, one of which encoded TRAIL, a death ligand. A high level of TRAIL mRNA was also found in the fetal liver of the lethally anemic DNase II(-/-) embryos, and a lack of IFN type I receptor in the DNase II(-/-) IFN-IR(-/-) embryos blocked the expression of TRAIL mRNA. However, a null mutation in TRAIL did not rescue the lethal anemia of the DNase II(-/-) embryos, indicating that TRAIL is dispensable for inducing the apoptosis of erythroid cells in DNase II(-/-) embryos, and therefore, that there is a TRAIL-independent mechanism for the IFN-induced apoptosis.

Role of Natural Interferon-α Producing Cells (Plasmacytoid Dendritic Cells) in Autoimmunity

The type I interferons (IFNs) have antiviral, cytostatic and prominent immunomodulatory effects, which all are of great importance during viral infections. However, prolonged exposure of the immune system to type I IFN can break tolerance and initiate an autoimmune reaction, eventually leading to autoimmune disease. Recent observations in patients with systemic lupus erythematosus (SLE) have revealed that such individuals have endogenous IFN-alpha inducers, causing an ongoing IFN-alpha production and consequently a continuous stimulation of the immune system. These IFN-alpha inducers consist of small immune complexes (IC) containing DNA or RNA and act on the principal IFN-alpha producing cell, the natural IFN-alpha producing cell (NIPC), also termed the plasmacytoid dendritic cell (PDC). The NIPC/PDC is a key cell in both the innate and adaptive immune response but can also, either directly or via produced IFN-alpha, have a pivotal role in autoimmunity. In this review we summarize recent data concerning NIPC/PDC, including their activation, regulation, function and possible role in autoimmune diseases, especially SLE.

The role of type I interferons in TLR responses

Recent advances in unravelling the complexities of the signalling pathways that constitute innate immunity have highlighted type I interferon as a key component in the response to infection. Here we focus on the emerging field of pattern-recognition receptor signalling, specifically Toll-like receptors and retinoic acid inducible gene-like helicases, from the perspective of this 50-year-old cytokine. The type I interferon gene family encompasses more than 20 subtypes, whose nature and properties have been extensively studied during its relatively long history. In this review we update and integrate available data on the mechanics of activation of the interferon genes and the role of this cytokine family in the innate immune response.

Mechanisms of Disease: primary Sjögren's syndrome and the type I interferon system

Sjögren's syndrome is a chronic autoimmune disease of largely unknown etiology and pathogenesis. The salivary and lacrimal glands are the main target organs, and key cells and molecules involved in the autoimmune process have been detected in these glands. Chemokines, expressed by epithelial cells, can attract T cells and dendritic cells that produce proinflammatory cytokines, which stimulate the immune response and induce apoptosis in the acinar and ductal epithelial cells. The autoantigens SSA and SSB are translocated to the apoptotic blebs and trigger infiltrating B cells to produce autoantibodies against SSA and SSB. Germinal-center-like structures can form within glandular lymphocyte foci, facilitating the antigen-driven B-cell activation. Many of the autoimmune mechanisms described above can be induced by type I interferon (IFN), and activation of this system in patients with Sjögren's syndrome has been described. A possible scenario is that an initial viral infection induces type I IFN production in salivary glands with a subsequent activation of the adaptive immune system. Resultant autoantibodies form nucleic-acid-containing immune complexes that can trigger prolonged type I IFN production, leading to a self-perpetuating autoimmune reaction. Several potential therapeutic targets for Sjögren's syndrome exist within the type I IFN system.

Soluble factors released by virus specific activated cytotoxic T-lymphocytes induce apoptotic death of astroglioma cell lines

Astrocytomas and astrogliomas represent the most common types of primary tumors in human central nervous system and are associated with high mortality due to the absence of efficient therapy. Here we demonstrate that, upon antigen-specific activation, cytotoxic T-lymphocytes (CTLs) secrete products that inhibit proliferation and induce apoptosis in a significant proportion of astroglioma cell lines. This effect is tumor specific in that normal cultured astrocytes do not develop apoptotic changes upon exposure to supernatant of activated CTLs. Experiments with purified lymphokines and lymphokine specific blocking antibodies indicate that synergistic activities of tumor necrosis factor (TNF)-alpha and interferon (INF)-gamma are required for the apoptosis inducing effect on some astroglioma cell lines. However, this effect appears to be dependent on additional factors produced by activated CTLs. Our results suggest that local application of factors released by activated CTLs or induction of CTL migration and activation in the tumor site may have a therapeutic effect in patients with astrogliomas.

Innate immune functions of microglia isolated from human glioma patients

Background

Innate immunity is considered the first line of host defense and microglia presumably play a critical role in mediating potent innate immune responses to traumatic and infectious challenges in the human brain. Fundamental impairments of the adaptive immune system in glioma patients have been investigated; however, it is unknown whether microglia are capable of innate immunity and subsequent adaptive anti-tumor immune responses within the immunosuppressive tumor micro-environment of human glioma patients. We therefore undertook a novel characterization of the innate immune phenotype and function of freshly isolated human glioma-infiltrating microglia (GIM).

Methods

GIM were isolated by sequential Percoll purification from patient tumors immediately after surgical resection. Flow cytometry, phagocytosis and tumor cytotoxicity assays were used to analyze the phenotype and function of these cells.

Results

GIM expressed significant levels of Toll-like receptors (TLRs), however they do not secrete any of the cytokines (IL-1β, IL-6, TNF-α) critical in developing effective innate immune responses. Similar to innate macrophage functions, GIM can mediate phagocytosis and non-MHC restricted cytotoxicity. However, they were statistically less able to mediate tumor cytotoxicity compared to microglia isolated from normal brain. In addition, the expression of Fas ligand (FasL) was low to absent, indicating that apoptosis of the incoming lymphocyte population may not be a predominant mode of immunosuppression by microglia.

Conclusion

We show for the first time that despite the immunosuppressive environment of human gliomas, GIM are capable of innate immune responses such as phagocytosis, cytotoxicity and TLR expression but yet are not competent in secreting key cytokines. Further understanding of these innate immune functions could play a critical role in understanding and developing effective immunotherapies to malignant human gliomas.

Increased expression and release of functional tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) by T cells from lupus patients with active disease

Increased expression of TRAIL in membrane-bound and soluble form in patients with systemic lupus erythematosus (SLE) has been previously reported. In this study, we characterized the upregulation of T-cell-associated and soluble TRAIL (sTRAIL) in vivo and the modulation of TRAIL expression and soluble protein release in vitro following T cell activation and IFNalpha exposure. The expression of membrane-bound TRAIL as determined by flow cytometry was higher on CD4(+) and CD8(+) T cells from lupus patients compared to controls, particularly on activated CD69(+)CD8(+) T cells. Similarly, sTRAIL levels determined by ELISA were significantly elevated in serum from patients with active SLE and correlated with levels of IFNalpha. In vitro, both T-cell-associated and sTRAIL were maximally induced by T cell activation plus IFNalpha in patients and controls. By Western blot analysis, sTRAIL was detected in sera in both the monomeric and multimeric, functional form. Both forms of TRAIL were functional in vitro as determined by Annexin V staining and (51)Cr release assay but the apoptotic activity of membrane TRAIL was 2.5-fold higher compared to that of sTRAIL. These results indicate that IFNalpha-induced enhancement of TRAIL expression and of TRAIL-mediated apoptosis may amplify the abnormal apoptotic process in SLE.

Activation of the interferon-alpha pathway identifies a subgroup of systemic lupus erythematosus patients with distinct serologic features and active disease

OBJECTIVE

Gene-expression studies have demonstrated increased expression of interferon (IFN)-inducible genes (IFIGs) in peripheral blood mononuclear cells (PBMCs) of many patients with systemic lupus erythematosus (SLE), with a predominant effect of type I IFN. This study examined the hypothesis that increased disease severity and activity, as well as distinct autoantibody specificities, characterize SLE patients with activation of the type I IFN pathway.

METHODS

Freshly isolated PBMCs from 77 SLE patients, 22 disease controls, and 28 healthy donors were subjected to real-time polymerase chain reaction for 3 IFIGs that are preferentially induced by IFNalpha, and the data were used to derive IFNalpha scores for all individuals. Expression of IFIGs was significantly higher in SLE patients compared with disease controls or healthy donors. SLE patients with high and low IFNalpha scores were compared for clinical manifestations of disease, disease severity, disease activity, serologic features, and potential confounders, by bivariate and multivariate analyses.

RESULTS

SLE patients with a high IFNalpha score had a significantly higher prevalence of renal disease, a greater number of American College of Rheumatology criteria for SLE, and a higher Systemic Lupus International Collaborating Clinics damage index (SDI) score than did SLE patients with low IFNalpha scores. Patients with high scores showed increased disease activity, as measured by lower C3 levels, hemoglobin levels, absolute lymphocyte counts, and albumin levels, and a higher anti-double-stranded DNA (dsDNA) titer, erythrocyte sedimentation rate, and SLE Disease Activity Index 2000 score. The presence of antibodies specific for Ro, U1 RNP, Sm, and dsDNA, but not phospholipids, was significantly associated with a high IFNalpha score. Logistic regression analysis confirmed that renal disease, higher SDI scores, low complement levels, and presence of anti-RNA binding protein (RBP) autoantibodies were associated with a high IFNalpha score.

CONCLUSION

Activation of the IFNalpha pathway defines a subgroup of SLE patients whose condition is characterized by increased disease severity, including renal disease, increased disease activity, reflected in complement activation, and autoreactivity to RBP.

Activation of the type I interferon system in primary Sjögren's syndrome: a possible etiopathogenic mechanism

OBJECTIVE

The etiopathogenesis of primary Sjögren's syndrome (SS) is largely unknown. In other autoimmune diseases, type I interferon (IFN) may play a pivotal role by triggering and sustaining the disease process. We therefore aimed to determine whether patients with primary SS had an activated type I IFN system.

METHODS

Salivary gland biopsy specimens and sera from patients with primary SS were investigated for the occurrence of IFNalpha-producing cells and measurable IFNalpha levels, respectively. The ability of primary SS sera together with apoptotic or necrotic cells to induce IFNalpha production in normal peripheral blood mononuclear cells was examined. The IFNalpha inducer was characterized, and IFNalpha-producing cells were identified. Clinical data were correlated with the IFNalpha-inducing capacity of primary SS sera.

RESULTS

Numerous IFNalpha-producing cells were detected in salivary gland biopsy specimens, despite low serum IFNalpha levels. Autoantibodies to RNA-binding proteins, combined with material released by necrotic or late apoptotic cells, were potent inducers of IFNalpha production in plasmacytoid dendritic cells (PDCs). This appeared to be attributable to RNA-containing immune complexes triggering PDCs by means of RNA and interaction with Fcgamma receptor IIa. The IFNalpha-inducing capacity of sera was associated with positive results of a labial salivary gland biopsy (focus score >/=1) and with dermatologic, hematologic, and pulmonary manifestations.

CONCLUSION

Patients with primary SS have an activated type I IFN system. Although virus may initiate the production of IFN, the continued IFNalpha synthesis is caused by RNA-containing immune complexes that activate PDCs to prolong IFNalpha production at the tissue level. This IFNalpha promotes the autoimmune process by a vicious circle-like mechanism, with increased autoantibody production and formation of more endogenous IFNalpha inducers.

Partial contribution of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/TRAIL receptor pathway to antitumor effects of interferon-alpha/5-fluorouracil against Hepatocellular Carcinoma

PURPOSE

Our purpose was to explore the contribution of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/TRAIL receptor pathway to antitumor effects of IFNalpha and 5-fluorouracil (5-FU) combination therapy for hepatocellular carcinoma (HCC).

EXPERIMENTAL DESIGN

Susceptibility of HCC cell lines to TRAIL and/or 5-FU was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The effects of 5-FU, IFNalpha, or both on the expression of TRAIL receptors (R1, R2, R3, and R4) on HCC cells or TRAIL in peripheral blood mononuclear cells (PBMC) were examined by flow cytometry. IFNalpha-induced cytotoxic effects of PBMC on HCC cell lines were examined by (51)Cr release assay. TRAIL expression in peripheral blood mononuclear cells and liver tissue from patients was examined by real-time reverse transcription-PCR or immunohistochemistry.

RESULTS

HLE and HepG2 were sensitive to TRAIL, but HuH7, PLC/PRF/5, and HLF were resistant. 5-FU had synergistic effect on TRAIL in HLF and additive effect in four other HCC cell lines. TRAIL receptors on HCC cells were up-regulated by 5-FU, and IFNalpha induced TRAIL on CD4(+) T cells, CD14(+) monocytes, and CD56(+) NK cells. Treatment of effector cells by IFNalpha and target HCC cells by 5-FU enhanced the cytotoxicity of CD14(+) monocytes and CD56(+) NK cells against HCC cells via a TRAIL-mediated pathway. TRAIL mRNA overexpression was noted in PBMC of HCC patients who clinically responded to IFNalpha/5-FU combination therapy, and TRAIL(+) mononuclear cells were found in cancer tissue of a responder.

CONCLUSION

Our results suggest that modulation of TRAIL/TRAIL receptor-mediated cytotoxic pathway might partially contribute to the anti-HCC effect of IFNalpha and 5-FU combination therapy.

Antiviral treatment with alpha interferon up-regulates CD14 on liver macrophages and its soluble form in patients with chronic hepatitis B

To investigate whether therapy with alpha interferon (IFN-alpha) induces changes in intrahepatic antigen-presenting cells (APCs), we obtained liver biopsy specimens before, during, and after therapy with IFN-alpha from chronic hepatitis B patients whose viral load had already been reduced by at least 8 weeks of treatment with lamivudine. HLA-DR, CD1a, and CD83 were not modified by the therapy. The intralobular expression of CD68 on Kupffer cells remained stable, denoting no changes in the number of resident macrophages during IFN-alpha treatment. In contrast, CD14 was weakly expressed in the absence of IFN-alpha and was significantly up-regulated during therapy. At the same time, the levels of soluble CD14 and interleukin-10 in plasma increased significantly. In vitro, monocytes maintained in the presence of IFN-alpha differentiated into macrophages or dendritic cells with higher levels of expression of CD14 than that for the control cultures. During therapy with IFN-alpha, T-cell infiltration in the portal spaces was reduced, mainly due to a significant decrease in the number of CD8(+) T cells. These findings show that IFN-alpha is biologically active on APCs in vivo and in vitro and suggest that this newly described regulatory function, together with the already known inhibitory effects on lymphocytes, may cooperate to reduce inflammation and consequent tissue damage in patients with chronic viral hepatitis.

Recruitment of dendritic cells in oral lichen planus

Using immunohistochemistry the presence of different dendritic cell (DC) subsets was analysed in 16 biopsies from patients with oral lichen planus (OLP). A significant increase of CD1a+/Langerin+ Langerhans cells, DC-SIGN+ DC and CD123+/BDCA2+ plasmacytoid DCs (PDCs) was found in the epithelium and in the stroma of OLP biopsies compared to normal oral mucosa. A proportion of DCs were mature DC-LAMP+ and expressed S100 or CD11c, typically found in the interdigitating DCs of nodal T-cell areas. Double staining revealed that mature DCs co-expressed CCR7, thus indicating the development of a nodal migratory phenotype upon maturation. Significant recruitment of PDCs producing IFN-alpha was demonstrated by the expression of MxA within the lichenoid inflammatory infiltrate and close cell-to-cell contacts between PDCs and mature DCs were observed, with a significant correlation between the numbers of these two populations. Moreover, PDCs were also found to contain Granzyme-B, an associated-cytotoxic granule protein, inducing target cell apoptosis. Taken together, these results suggest that PDCs may promote maturation of DCs and amplify the cytotoxicity of lymphoid cells. Finally, the recruitment of different subtypes of DC, such as Langerhans cells, stromal DC-SIGN+ DCs and PDCs, associated with a significant proportion of mature DCs, acquiring a CCR7+ 'migratory' phenotype, indicate that they may play a pivotal role in the development of the lichenoid inflammatory infiltrate that occurs typically in OLP.

Coordinate overexpression of interferon-alpha-induced genes in systemic lupus erythematosus

OBJECTIVE

To study the contribution of interferon-alpha (IFNalpha) and IFNgamma to the IFN gene expression signature that has been observed in microarray screens of peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE).

METHODS

Quantitative real-time polymerase chain reaction analysis of healthy control PBMCs was used to determine the relative induction of a panel of IFN-inducible genes (IFIGs) by IFNalpha and IFNgamma. PBMCs from 77 SLE patients were compared with those from 22 disease controls and 28 healthy donors for expression of IFIGs.

RESULTS

Expression of IFNalpha-inducible genes was significantly higher in SLE PBMCs than in those from disease controls or healthy donors. The level of expression of all IFIGs in PBMCs from SLE patients with IFNalpha pathway activation correlated highly with the inherent responsiveness of those genes to IFNalpha, suggesting coordinate activation of that cytokine pathway. Expression of genes preferentially induced by IFNgamma was not significantly increased in SLE PBMCs compared with control PBMCs. IFNalpha-regulated gene-inducing activity was detected in some SLE plasma samples.

CONCLUSION

The coordinate activation of IFNalpha-induced genes is a characteristic of PBMCs from many SLE patients, supporting the hypothesis that IFNalpha is the predominant stimulus for IFIG expression in lupus.

Expansion of bone marrow IFN-alpha-producing dendritic cells in New Zealand Black (NZB) mice: high level expression of TLR9 and secretion of IFN-alpha in NZB bone marrow

Patients with systemic lupus erythematosus have elevated IFN-alpha production. Furthermore, sera IFN-alpha levels correlate with disease activity. We have focused our attention on whether this phenotype is also seen in the New Zealand Black (NZB) mice and simultaneously addressed the underlying mechanisms. Specifically, we analyzed: 1) levels of sera IFN-alpha after type A CpG ODN 2216 injection in autoimmunity-prone NZB and control mice, and 2) levels of IFN-alpha synthesized by IFN-alpha-producing dendritic cells (IPDCs) using highly enriched populations of CD11c+B220+ IPDCs derived from NZB and control mice; IPDCs are divided into two subpopulations (CD4+CD11c+B220+ and CD4-CD11c+B220+). Our data demonstrate that NZB mice produced higher levels of sera IFN-alpha after type A CpG ODN 2216 injection when compared with control mice (p < 0.01). In addition, the cell numbers, frequency, and TLR9 mRNA levels of CD4+ and CD4- IPDC were markedly increased in the bone marrow (BM) of NZB mice. Upon in vitro stimulation with TLR9 ligand-CpG ODN 2216, higher levels of IFN-alpha were synthesized by IPDCs from the BM of NZB. The major contributor of IFN-alpha was the CD4-CD11c+B220+ IPDC subpopulation. Furthermore, NZB BM IPDCs manifest impaired expression of homing chemokine CCR7 and CD62L, and IL-12 production. These data on the functional characteristics of the IPDC lineages explain in part the mechanism of hyper-IFN-alpha production and help clarify the mechanism for the expansion of NZB BM IPDCs.

Interferon-α in systemic lupus erythematosus

PURPOSE OF REVIEW

To describe the lines of evidence supporting a significant role for interferon-alpha (IFNalpha) in the pathogenesis of systemic lupus erythematosus (SLE) and to propose potential mechanisms by which IFNalpha contributes to the autoimmunity and immune dysfunction of SLE.

RECENT FINDINGS

Long-standing data indicating elevated levels of IFNalpha in the circulation of patients with SLE have recently been supplemented by reports from clinical practice, gene expression data, analysis of patient cells studied ex vivo, and studies of mechanisms of induction of IFNalpha production to provide complementary data strongly supporting a pathogenic role for IFNalpha in SLE. Recombinant IFNalpha, when administered as a therapy to patients with malignancy or hepatitis infection, can induce SLE. IFNalpha-regulated genes are highly expressed in SLE peripheral blood cells compared with cells from control subjects. Functional alterations of SLE mononuclear cells have been attributed to effects of IFNalpha. In addition, immune complexes bearing lupus autoantibodies and RNA or DNA have been shown to induce IFNalpha production. Finally, progress in understanding the role of Toll-like receptors (TLR) in the activation of the innate immune response has suggested potential mechanisms by which adjuvant-like factors act through TLR to induce IFNalpha as well as effective processing of self-antigens, resulting in activation of an adaptive immune response directed against self, as well as cytokine-mediated immune dysfunction.

SUMMARY

Substantial evidence supports a significant role for IFNalpha in the pathogenesis of lupus. The IFNalpha pathway represents a promising target for therapeutic intervention in patients with SLE.

NK-cell purging of leukemia: superior antitumor effects of NK cells H2 allogeneic to the tumor and augmentation with inhibitory receptor blockade

Natural killer (NK) cells are composed of subsets characterized by the expression of inhibitory or activating receptors, or both, specific for different major histocompatibility complex (MHC) class I determinants. We have previously shown that inhibitory receptor blockade of syngeneic NK cells was an effective means of ex vivo purging of leukemia-contaminated bone marrow and that the transplantation of mice with the purged bone marrow cells (BMCs) resulted in long-term, relapse-free survival. We have extended the investigation to assess the antitumor effects mediated by NK cells H2-allogeneic to tumor cells. We demonstrate that various tumor cell lines are more susceptible to lysis by H2-allogeneic NK cells than by syngeneic NK cells in vitro even though comparable percentages of Ly49 NK cells were present. Using allogeneic NK cells to purge leukemia-contaminating BMCs before transplantation resulted in a higher proportion of mice with long-term survival than using syngeneic NK cells. Allogeneic NK cells did not suppress hematopoietic reconstitution as measured by granulocyte/monocyte-colony-forming unit (CFU-GM), complete blood count (CBC), and donor chimerism at various days after transplantation. Inhibitory receptor blockade of allogeneic NK cells also significantly increased these antitumor effects at lower NK/tumor ratios compared with those of syngeneic NK cells. These results demonstrate that H2-allogeneic NK cells mediate more potent antitumor effects than syngeneic NK cells without adverse hematologic effects and thus may be useful in cancer therapy.

Microarray analysis of gene expression in lupus

Recent advances in the study of global patterns of gene expression with the use of microarray technology, coupled with data analysis using sophisticated statistical algorithms, have provided new insights into pathogenic mechanisms of disease. Complementary and reproducible data from multiple laboratories have documented the feasibility of analysis of heterogeneous populations of peripheral blood mononuclear cells from patients with rheumatic diseases through use of this powerful technology. Although some patterns of gene expression, including increased expression of immune system cell surface activation molecules, confirm previous data obtained with other techniques, some novel genes that are differentially expressed have been identified. Most interesting is the dominant pattern of interferon-induced gene expression detected among blood mononuclear cells from patients with systemic lupus erythematosus and juvenile dermatomyositis. These data are consistent with longstanding observations indicating increased circulating interferon-alpha in the blood of patients with active lupus, but draw attention to the dominance of the interferon pathway in the hierarchy of gene expression pathways implicated in systemic autoimmunity.

The hypothalamic-pituitary-adrenal axis and viral infection

The hypothalamic-pituitary-adrenal (HPA) axis plays an important immunomodulatory role during viral infection. Activation of the HPA axis ultimately leads to elevated plasma levels of glucocorticoid (GC) hormones with the ability to mediate adaptive behavioral, metabolic, cardiovascular and immune system effects. In this review, we focus on the modulation of anti-viral immunity and viral pathogenesis by the HPA axis.

Expression of the markers BDCA-2 and BDCA-4 and production of interferon-alpha by plasmacytoid dendritic cells in systemic lupus erythematosus

OBJECTIVE

To study the expression of blood dendritic cell antigen 2 (BDCA-2) and BDCA-4 molecules by plasmacytoid dendritic cells (PDCs) in the blood of patients with systemic lupus erythematosus (SLE), and to study PDC production of interferon-alpha (IFN alpha) and its inhibition by anti-BDCA-2 and anti-BDCA-4 antibodies.

METHODS

Peripheral blood mononuclear cells (PBMCs) from SLE patients (SLE PBMCs) and from healthy controls were induced to produce IFN alpha in vitro by SLE serum containing an endogenous IFN alpha-inducing factor (SLE-IIF) or by herpes simplex virus type 1 (HSV-1). The frequencies and numbers of BDCA-2-, BDCA-3-, and BDCA-4-expressing cells were analyzed by flow cytometry, and the effects of anti-BDCA-2 and anti-BDCA-4 monoclonal antibodies (mAb) on IFN alpha production were investigated.

RESULTS

IFN alpha production by SLE PBMCs induced by SLE-IIF or HSV-1 was decreased compared with that of healthy control PBMCs (P = 0.002 and P = 0.0007, respectively). The proportions of BDCA-2- and BDCA-3-expressing cells in SLE PBMCs were reduced compared with those in PBMCs from healthy controls (P = 0.01 and P = 0.004, respectively). IFN alpha producers in culture, especially among SLE PBMCs, displayed reduced BDCA-2 expression and constituted only a minority of the BDCA-2-positive cells, at least in healthy control PBMCs (median 18%). IFN alpha production by both SLE and healthy control PBMCs stimulated by SLE-IIF or HSV-1 was markedly reduced by anti-BDCA-2 mAb (median 81-98% inhibition). Anti-BDCA-4 mAb only partially inhibited SLE-IIF-induced IFN alpha production.

CONCLUSION

SLE patients had a reduced number of BDCA-2-expressing PDCs, also termed natural IFN alpha-producing cells, and their IFN alpha production could be inhibited by anti-BDCA-2/4 mAb. Such mAb may be a therapeutic option for inhibiting the ongoing IFN alpha production in SLE patients.

Interferons and apoptosis

The interferons (IFNs), in addition to their well-known antiviral activities, have important roles in the control of cell proliferation and are effective agents for the treatment of a limited number of malignant diseases. IFNs not only regulate cell growth and division but also influence cell survival through their effects on apoptosis. This review describes the current state of knowledge about the mechanisms of action of these cytokines on the apoptotic machinery, with particular emphasis on the synergism that exists between the IFNs and other proapoptotic agents, such as members of the tumor necrosis factor (TNF) family. The review also discusses the physiologic and clinical implications of the effects of the IFNs on apoptosis for regulation of viral infection and tumor growth.

Systemic lupus erythematosus and the type I interferon system

Patients with systemic lupus erythematosus (SLE) have ongoing interferon-alpha (IFN-alpha) production and serum IFN-alpha levels are correlated with both disease activity and severity. Recent studies of patients with SLE have demonstrated the presence of endogenous IFN-alpha inducers in such individuals, consisting of small immune complexes (ICs) containing IgG and DNA. These ICs act specifically on natural IFN-alpha-producing cells (NIPCs), often termed plasmacytoid dendritic cells (PDCs). Given the fact that the NIPC/PDC has a key role in both the innate and adaptive immune response, as well as the many immunoregulatory effects of IFN-alpha, these observations might be important for the understanding of the etiopathogenesis of SLE. In this review we briefly describe the biology of the type I IFN system, with emphasis on inducers, producing cells (especially NIPCs/PDCs), IFN-alpha actions and target immune cells that might be relevant in SLE. On the basis of this information and results from studies in SLE patients, we propose a hypothesis that explains how NIPCs/PDCs become activated and have a pivotal etiopathogenic role in SLE. This hypothesis also indicates new therapeutic targets in this autoimmune disease.

Antiapoptotic effect of interferon-alpha on hepatic stellate cells (HSC): a novel pathway of IFN-alpha signal transduction via Janus kinase 2 (JAK2) and caspase-8

The hepatic stellate cell (HSC), the pericyte of the liver sinusoids belongs to the mesenchymal cells of the liver. Damaging noxae induce a transformation from the quiescent (vitamin A-storing cell) to the activated (connective tissue-producing cell) state. The balance between proapoptotic and surviving factors decides about the fate of the activated HSC. Interferon-alpha (IFN-alpha) has been shown to elicit antiproliferative and/or antifibrogenic effects in various cell types of mesenchymal origin. We therefore investigated the effect of IFN-alpha on primary cultured rat HSC in their quiescent (day 2) and activated state (day 7). IFN-alpha significantly inhibited spontaneous apoptosis in activated HSC in vitro and simultaneously inhibited cell cycle progression by inducing a G1 arrest. The effect of IFN-a is not accompanied by a modulation of CD95, CD95L, p53, p21(WAF1), p27, bcl-2, bcl-xL, bax, NFkappaB, or IkappaB gene expression. Surprisingly, the IFN-alpha effect could be abolished completely by blocking JAK2 activity or JAK2 translation. The downregulating effect of IFN-alpha on the activity of caspase-8 and caspase-3 could also be neutralized using tyrphostin AG490 or JAK-2 antisense. Taken together IFN-alpha inhibits apoptosis of activated HSC by activation of JAK2 which inhibits the caspase-8 apoptosis pathway.

Effects of interferon-alpha on gene expression of chemokines and members of the tumour necrosis factor superfamily in HIV-infected patients

We examined the effect of interferon (IFN)-alpha on the expression of 375 genes relevant to inflammatory and immunological reactions in peripheral blood mononuclear cells (PBMC) from HIV-infected patients by cDNA expression array and real-time quantitative RT-PCR. Our main findings were: (i) IFN-alpha induced up-regulation of several genes in the tumour necrosis factor (TNF) superfamily including the ligands APRIL, FasL, TNF-alpha and TRAIL, with particularly enhancing effects on the latter in HIV-infected patients. (ii) While IFN-alpha markedly up-regulated the expression of anti-angionetic ELR- CXC-chemokines (e.g. MIG and IP-10), it suppressed the expression of angiogenic ELR+ CXC-chemokines (e.g. GRO-alpha, IL-8 and ENA-78), with similar patterns in both patients and controls. (iii) IFN-alpha induced a marked increase in gene expression of the HIV co-receptor CCR5 in both patients and controls. We suggest that these effects may contribute to both the therapeutic and toxic effects of IFN-alpha. Moreover, our findings underscore that the biological effects of IFN-alpha in HIV infection are complex and that the clinical net effects of IFN-alpha treatment may be difficult to predict. However, the potent enhancing effect of IFN-alpha on several pro-apoptotic genes in the TNF superfamily and the enhancing effect on CCR5 expression suggest a possible pathogenic role of IFN-alpha in the progression of HIV-related immunodeficiency and suggests caution in the therapeutic use of IFN-alpha in HIV-infected -individuals.

T cell proliferation induced by autologous non-T cells is a response to apoptotic cells processed by dendritic cells

Self-reactive T cells are present in the mature immune repertoire as demonstrated by T cell proliferation induced by autologous non-T cells in the autologous mixed lymphocyte reaction. This reaction generates regulatory T cells in vitro and may reflect immune regulatory pathways in vivo, but the antigenic peptides recognized remain uncharacterized. We revisited this issue in light of the importance of apoptosis in immune regulation. We found that apoptosis among peripheral blood non-T stimulator cells is associated with augmented induction of autologous T cell proliferation. Our data show that caspase activity in the non-T stimulator population is essential for induction of autologous T cell proliferation, suggesting that cellular components in the non-T cell fraction are enzymatically modified, most likely by effector caspases, and have a direct or indirect effect on autoreactive T cell activation. Furthermore, exposure of macrophage-derived dendritic cells to apoptotic non-T cells augments autologous T cell proliferation, and blockade of alpha(v)beta(5) integrin, but not alpha(v)beta(3), inhibits the capacity of irradiated non-T cells or dendritic cells to stimulate autologous T cell proliferation. These experiments, using an entirely autologous system, suggest the interpretation that autoreactive T cells may recognize self-Ags modified through the actions of caspases and presented to T cells by dendritic cells. Induction of an in vivo autologous mixed lymphocyte reaction by caspase-modified self-Ags present in apoptotic cells may represent a mechanism to maintain peripheral immune tolerance.

Response of hairy cells to IFN-alpha involves induction of apoptosis through autocrine TNF-alpha and protection by adhesion

Although hairy cell leukemia is uniquely sensitive to interferon-alpha (IFN-alpha), the biologic basis for this phenomenon remains unclear. Here we examine the effects of IFN-alpha on cultured hairy cells (HCs), taking into account the possible modifying influence of cell adhesion. We make the novel observation that therapeutic concentrations of IFN-alpha kill nonadherent HCs by inducing apoptosis. In keeping with the persistence of HCs in tissues during therapy, such killing was inhibited by integrin-mediated adhesion to vitronectin or fibronectin. Exposure of HCs to IFN-alpha resulted in a marked increase in tumor necrosis factor-alpha (TNF-alpha) secretion. Furthermore, blocking antibodies to TNF-RI or TNF-RII protected HCs from IFN-alpha-induced apoptosis, demonstrating that such killing was mediated by TNF-alpha. In the absence of IFN-alpha, exogenous TNF-alpha did not induce HC apoptosis, showing that IFN-alpha sensitized HCs to the proapoptotic effect of autocrine TNF-alpha. This sensitization to TNF-alpha-induced killing was attributable to suppression of IAP (inhibitors of apoptosis) production known to be regulated by the cytoprotective nuclear factor-kappaB-dependent arm of TNF-alpha signaling. Moreover, engagement of the receptors for fibronectin or vitronectin prevented this IFN-alpha-induced down-regulation of IAPs. Understanding of the signals involved in the combined effects of IFN-alpha and TNF-alpha and abrogation of those induced by integrin engagement offers the possibility of sensitizing other malignant cells to IFN-alpha-induced killing and thereby extending the therapeutic use of this cytokine.

Lack of requirement of STAT1 for activation of nuclear factor-kappaB, c-Jun NH2-terminal protein kinase, and apoptosis by tumor necrosis factor-alpha

Tumor necrosis factor (TNF) is one of the most potent activators of nuclear transcription factor NF-kappaB, c-Jun N-terminal protein kinase (JNK), and apoptosis in a wide variety of cells. The biological effects of TNF are mediated through sequential interactions of various cytoplasmic proteins with intracellular domains of TNF receptors. Whether signal transducer and activator of transcription-1 (STAT1), which mediates interferon (IFN) signaling, also plays any role in the TNF-mediated activation of NF-kappaB, JNK, and apoptosis has not been established. Here, we report our investigation of the role of STAT1 in TNF signaling using STAT1-deficient U3A and STAT1-stably transfected U3A-PSG91 cells. IFNalpha inhibited the proliferation of STAT1-expressing U3A-PSG91 cells but had no effect on STAT1-negative U3A cells. TNF alone, even up to 10 nM, had no effect on the proliferation of either U3A-PSG91 or U3A cells. Irrespective of STAT1 status, TNF induced cytotoxic effects in the presence of cycloheximide (CHX) in both cell types. Additionally, TNF-induced caspase-3 and caspase-8 activation and TNF-induced PARP cleavage were unaffected by the presence or absence of STAT1. TNF activated NF-kappaB, consisting of p50 and p65, in both U3A and U3A-pSG91 cells in a dose- and time-dependent manner, but the degree and rate of activation were slightly lower in U3A cells, as were IkappaBalpha degradation and NF-kappaB-dependent reporter gene expression. STAT1 was, however, required for IFNalpha-mediated downregulation of TNF-induced NF-kappaB activation. TNF activated JNK in both cell types, but dose and time of exposure required for optimum activation differed slightly. Thus, overall our results indicate that STAT1 plays a minimal role in TNF-mediated cellular responses.

Interferon-beta treatment of experimental autoimmune encephalomyelitis leads to rapid nonapoptotic termination of T cell infiltration

We investigated the possible mechanisms how interferon (IFN)-beta may control T cell infiltration in the CNS in experimental autoimmune encephalomyelitis (EAE). Adoptive transfer (AT) EAE was induced in groups of six female Lewis rats. Animals were treated with 3 x 10(5) units of recombinant rat IFN-beta s.c. once at 18 hr, or with 10 mg/kg methylprednisolone (MP) i.v. twice at 18 and 6 hr prior to dissection, or with a combination of both. T cell apoptosis was detected by immunohistochemistry on paraffin sections of spinal cord, using morphological criteria and TUNEL staining. Double labeling of immune cells was done for tumor necrosis factor (TNF)-alpha and metalloproteinase (MMP) 2. Disruption of the blood-brain barrier (BBB) was visualized by staining for albumin. In severe EAE, an increase of T cell apoptosis was seen after IFN-beta alone (all data presented as mean +/- SD: 24.5% +/- 2.2%, P < 0.05, vs. 19.4% +/- 3.1% in controls), and in combination with MP (29.4% +/- 7.3%, P < 0.05 vs. controls). Only the combination therapy decreased T cell infiltration (53.9 +/- 17.7 cells/mm(2), P < 0.05, vs. 99.5 +/- 35.2 cells/mm2 in controls). In moderate EAE, the rate of T cell apoptosis was slightly increased after IFN-beta (21.2% +/- 5.2% vs. 17.4% +/- 5.0% in controls), whereas MP alone (25.5% +/- 3.5%, P < 0.01 vs. controls) and the combination therapy (22.4% +/- 4.8%, P < 0.05 vs. controls) had a clear augmenting effect. IFN-beta tended to decrease T cell infiltration (46.1 +/- 12.7 cells/mm2) compared to controls (59.2 +/- 18.5 cells/mm2). The rate of TNF-alpha-expressing T cells was significantly decreased by IFN-beta and in combination with MP. Also, TNF-alpha expression in macrophages was significantly reduced by IFN-beta and by the combination therapy. The rate of MMP2-expressing macrophages was lower after IFN-beta but clearly decreased only in combination with MP. BBB disruption was ameliorated after IFN-beta but significantly only in combination with MP. Our study indicates that IFN-beta affects the immunopathological process in EAE in several ways, but apoptosis appears as a minor component. In view of treatment of MS relapses, the synergistic effects in this study corroborate the use of a combination therapy with high-dose MP and IFN-beta.