Perforin: more than just an effector molecule

Lipopeptides development in cosmetics and pharmaceutical applications: A comprehensive review

Lipopeptides are surface active, natural products of bacteria, fungi and green-blue algae origin, having diverse structures and functionalities. In analogy, a number of chemical synthesis techniques generated new designer lipopeptides with desirable features and functions. Lipopetides are self-assembly guided, supramolecular compounds which have the capacity of high-density presentation of the functional epitopes at the surface of the nanostructures. This feature contributes to their successful application in several industry sectors, including food, feed, personal care, and pharmaceutics. In this comprehensive review, the novel class of ribosomally synthesized lipopeptides is introduced alongside the more commonly occuring non-ribosomal lipopeptides. We highlight key representatives of the most researched as well as recently described lipopeptide families, with emphasis on structural features, self-assembly and associated functions. The common biological, chemical and hybrid production routes of lipopeptides, including prominent analogues and derivatives are also discussed. Furthermore, genetic engineering strategies aimed at increasing lipopeptide yields, diversity and biological activity are summarized and exemplified. With respect to application, this work mainly details the potential of lipopeptides in personal care and cosmetics industry as cleansing agents, moisturizer, anti-aging/anti-wrinkling, skin whitening and preservative agents as well as the pharmaceutical industry as anitimicrobial agents, vaccines, immunotherapy, and cancer drugs. Given that this review addresses human applications, we conclude on the topic of safety of lipopeptide formulations and their sustainable production.

Noncytotoxic functions of killer cell granzymes in viral infections

Cytotoxic lymphocytes produce granules armed with a set of 5 serine proteases (granzymes (Gzms)), which, together with the pore-forming protein (perforin), serve as a major defense against viral infections in humans. This granule-exocytosis pathway subsumes a well-established mechanism in which target cell death is induced upon perforin-mediated entry of Gzms and subsequent activation of various (apoptosis) pathways. In the past decade, however, a growing body of evidence demonstrated that Gzms also inhibit viral replication and potential reactivation in cell death–independent manners. For example, Gzms can induce proteolysis of viral or host cell proteins necessary for the viral entry, release, or intracellular trafficking, as well as augment pro-inflammatory antiviral cytokine response. In this review, we summarize current evidence for the noncytotoxic mechanisms and roles by which killer cells can use Gzms to combat viral infections, and we discuss the potential thereof for the development of novel therapies.

Should we stimulate or suppress immune responses in COVID-19? Cytokine and anti-cytokine interventions

The coronavirus disease-19 pandemic (COVID-19), which appeared in China in December 2019 and rapidly spread throughout the world, has forced clinicians and scientists to take up extraordinary challenges. This unprecedented situation led to the inception of numerous fundamental research protocols and many clinical trials. It quickly became apparent that although COVID-19, in the vast majority of cases, was a benign disease, it could also develop a severe form with sometimes fatal outcomes. Cytokines are central to the pathophysiology of COVID-19; while some of them are beneficial (type-I interferon, interleukin-7), others appear detrimental (interleukin-1β, -6, and TNF-α) particularly in the context of the so-called cytokine storm. Yet another characteristic of the disease has emerged: concomitant immunodeficiency, notably involving impaired type-I interferon response, and lymphopenia. This review provides an overview of current knowledge on COVID-19 immunopathology. We discuss the defective type-I IFN response, the theoretical role of IL-7 to restore lymphocyte repertoire, as well as we mention the two patterns observed in severe COVID-19 (i.e. interleukin-1β-driven macrophage activation syndrome vs. interleukin-6-driven immune dysregulation). Next, reviewing current evidence drawn from clinical trials, we examine a number of cytokine and anti-cytokine therapies, including interleukin-1, -6, and TNF inhibitors, as well as less targeted therapies, such as corticosteroids, chloroquine, or JAK inhibitors.

Should we stimulate or suppress immune responses in COVID-19? Cytokine and anti-cytokine interventions

The coronavirus disease-19 pandemic (COVID-19), which appeared in China in December 2019 and rapidly spread throughout the world, has forced clinicians and scientists to take up extraordinary challenges. This unprecedented situation led to the inception of numerous fundamental research protocols and many clinical trials. It quickly became apparent that although COVID-19, in the vast majority of cases, was a benign disease, it could also develop a severe form with sometimes fatal outcomes. Cytokines are central to the pathophysiology of COVID-19; while some of them are beneficial (type-I interferon, interleukin-7), others appear detrimental (interleukin-1β, -6, and TNF-α) particularly in the context of the so-called cytokine storm. Yet another characteristic of the disease has emerged: concomitant immunodeficiency, notably involving impaired type-I interferon response, and lymphopenia. This review provides an overview of current knowledge on COVID-19 immunopathology. We discuss the defective type-I IFN response, the theoretical role of IL-7 to restore lymphocyte repertoire, as well as we mention the two patterns observed in severe COVID-19 (i.e. interleukin-1β-driven macrophage activation syndrome vs. interleukin-6-driven immune dysregulation). Next, reviewing current evidence drawn from clinical trials, we examine a number of cytokine and anti-cytokine therapies, including interleukin-1, -6, and TNF inhibitors, as well as less targeted therapies, such as corticosteroids, chloroquine, or JAK inhibitors.

Less aggressive disease in patients with primary squamous cell carcinomas of the thyroid gland and coexisting lymphocytic thyroiditis

Aim of the study

Primary squamous cell carcinoma (SCC) of the thyroid gland is extremely rare. Infrequently, primary SCC of the thyroid gland is accompanied by other thyroid diseases such as Hashimoto's thyroiditis (HT). Recently, studies have demonstrated that differentiated thyroid cancer with coexisting HT has a better prognosis. However, the prognosis of patients with primary SCC of the thyroid gland and coexistent HT has not been clearly identified. We compared the clinical characteristics and disease stages of patients with primary SCC with and without lymphocytic thyroiditis (LT).

Material and methods

We reviewed reports of primary SCC of the thyroid gland published in the English literature.

Results and conclusions

We identified 46 papers that included 17 cases of primary SCC of the thyroid gland with LT and 77 cases of primary SCC of the thyroid gland without LT. Lymph node metastasis and local invasion rates did not differ between these two groups. Distant metastases were absent in patients with LT, and were observed in 13 (16.9%) patients without LT. A greater proportion of patients without LT had advanced stage disease (stage IV A-B-C) than patients with LT (p < 0.05). Patients with primary SCC of the thyroid gland and coexisting LT had lower tumour-node-metastasis stage and frequency of distant metastasis than those without LT. Lymphocytic infiltration in patients with SCC appears to limit tumour growth and distant metastases.

Chronic HCV infection affects the NK cell phenotype in the blood more than in the liver

Although epidemiological and functional studies have implicated NK cells in protection and early clearance of HCV, the mechanism by which they may contribute to viral control is poorly understood, particularly at the site of infection, the liver. We hypothesized that a unique immunophenotypic/functional NK cell signature exists in the liver that may provide insights into the contribution of NK cells to viral control. Intrahepatic and blood NK cells were profiled from chronically infected HCV-positive and HCV-negative individuals. Baseline expression of activating and inhibitory receptors was assessed, as well as functional responses following stimulation through classic NK cell pathways. Independent of HCV infection, the liver was enriched for the immunoregulatory CD56^bright NK cell population, which produced less IFNγ and CD107a but comparable levels of MIP1β, and was immunophenotypically distinct from their blood counterparts. This profile was mostly unaltered in chronic HCV infection, though different expression levels of NKp46 and NKG2D were associated with different grades of fibrosis. In contrast to the liver, chronic HCV infection associated with an enrichment of CD161^lowperforin^high NK cells in the blood correlated with increased AST and 2B4 expression. However, the association of relatively discrete changes in the NK cell phenotype in the liver with the fibrosis stage nevertheless suggests an important role for the NK response. Overall these data suggest that tissue localization has a more pervasive effect on NK cells than the presence of chronic viral infection, during which these cells might be mostly attuned to limiting immunopathology. It will be important to characterize NK cells during early HCV infection, when they should have a critical role in limiting infection.

Understanding disease processes in multiple sclerosis through magnetic resonance imaging studies in animal models

There are exciting new advances in multiple sclerosis (MS) resulting in a growing understanding of both the complexity of the disorder and the relative involvement of grey matter, white matter and inflammation. Increasing need for preclinical imaging is anticipated, as animal models provide insights into the pathophysiology of the disease. Magnetic resonance (MR) is the key imaging tool used to diagnose and to monitor disease progression in MS, and thus will be a cornerstone for future research. Although gadolinium-enhancing and T₂ lesions on MRI have been useful for detecting MS pathology, they are not correlative of disability. Therefore, new MRI methods are needed. Such methods require validation in animal models. The increasing necessity for MRI of animal models makes it critical and timely to understand what research has been conducted in this area and what potential there is for use of MRI in preclinical models of MS. Here, we provide a review of MRI and magnetic resonance spectroscopy (MRS) studies that have been carried out in animal models of MS that focus on pathology. We compare the MRI phenotypes of animals and patients and provide advice on how best to use animal MR studies to increase our understanding of the linkages between MR and pathology in patients. This review describes how MRI studies of animal models have been, and will continue to be, used in the ongoing effort to understand MS.

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MRI studies of pathology in various animal models of MS are reviewed.

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MRI phenotypes in animal models of MS and MS patients are compared.

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Animal MRI can increase understanding of links between MR and pathology in patients.

The PFP/RAG2 double-knockout mouse in metastasis research: small-cell lung cancer and prostate cancer

Patients with small-cell lung cancer (SCLC) and prostate cancer (PCa) as well as other solid tumors may have micro- or macro-metastatic spread at an early stage of the disease. SCLC and PCa xenograft transfer models in immunodeficient mice fail to model this metastatic spread in vivo. In both tumor types the depletion of NK cells found in immunodeficient mice results in an increased number of spontaneous metastases, mirroring the clinical situation where NK cell activity in patients is related to metastatic spread of the disease. As a result NK cell activity directly influences treatment options and mortality. Newly developed immunodeficient mouse strains lacking functional T- and B-cells (rag2 knockout) however presenting functional NK cells (perforin knockout) are superior in producing spontaneous metastasis of SCLC and PCa cells compared to the system using SCID mice.

An emerging role for Serine Protease Inhibitors in T lymphocyte immunity and beyond

Serine proteases control a wide variety of physiological and pathological processes in multi-cellular organisms, including blood clotting, cancer, cell death, osmo-regulation, tissue re-modeling and immunity to infection. T lymphocytes are required for adaptive cell mediated immunity and serine proteases are not only important for effector function but also homeostatic regulation of cell numbers. Serine Protease Inhibitors (Serpins) are the physiological regulators of serine proteases activity. In this review, I will discuss the role of serpins in controlling the recognition of antigen, effector function and homeostatic control of T lymphocytes through the inhibition of physiological serine protease targets. An emerging view of serpins is that they are important promoters of cellular viability through their inhibition of executioner proteases. This will be discussed in the context of the T lymphocyte survival during effector responses and the development and persistence of long-lived memory T cells. The potent anti-apoptotic properties of serpins can also work against adaptive cell immunity by protecting viruses and tumors from eradication by cytotoxic T cells (CTL). Recent insights from knock-out mouse models demonstrate that these serpins also are required for hematological progenitor cells and so are critical for the development of lineages other than T lymphocytes. Given the emerging role of serpins in multiple aspects of lymphocyte immunity and blood development I will review the progress to date in developing new immunotherapeutic approaches based directly on serpins or knowledge gained from identifying their physiologically relevant protease targets.

NK cells regulate CD8+ T cell priming and dendritic cell migration during influenza A infection by IFN-γ and perforin-dependent mechanisms

An effective immune response against influenza A infection depends on the generation of virus-specific T cells. NK cells are one of the first-line defenses against influenza A infection. We set out to delineate the role of NK cells in T cell immunity using a murine model of influenza A infection with A/PR/8/34. We show that early T cell recruitment mainly occurs in the posterior mediastinal lymph node (pMLN). Depletion of NK cells significantly impaired both dendritic cell (DC) and T cell recruitment into the pMLN. A similar reduction of T cell recruitment was observed when migration was blocked by pertussis toxin, suggesting that migration of pulmonary NK cells and DCs regulates cell recruitment to the pMLN. T cell recruitment was dependent on IFN-γ, and transfer of IFN-γ-competent naive NK cells into IFN-γ-/- mice restored T cell recruitment, whereas IFN-γ-deficient NK cells failed to do so. In addition, NK cell depletion reduced the uptake and transport of influenza A virus by DCs, and significantly impaired the virus-specific T cell response. Both IFN-γ-/- and perforin-/- mice showed reduced viral Ag transport by DCs, suggesting that the ability of NK cells to influence virus transport depends on IFN-γ and perforin. In summary, our data suggest that NK cells play a critical role in the initiation and shaping of the T cell response after influenza A infection.

Serine protease inhibitors and cytotoxic T lymphocytes

Serine proteases control a wide variety of physiological and pathological processes in multi-cellular organisms, including blood clotting, cancer, cell death, osmoregulation, tissue remodeling, and immunity to infection. Cytotoxic T lymphocytes (CTLs) are required for adaptive cell-mediated immunity to intracellular pathogens by killing infected cells and through the development of memory T cells. Serine proteases not only allow a CTL to kill but also impose homeostatic control on CTL number. Serine protease inhibitors (serpins) are the physiological regulators of serine proteases' activity. In this review, I discuss the role of serpins in controlling the recognition of antigen, effector function, and homeostatic control of CTLs through the inhibition of physiological serine protease targets. An emerging view of serpins is that they are important promoters of cellular viability through their inhibition of executioner proteases. This view is discussed in the context of the T-lymphocyte survival during effector responses and the development and persistence of long-lived memory T cells. Given the important role serpins play in CTL immunity, I discuss the potential for developing new immunotherapeutic approaches based directly on serpins or knowledge gained from identifying their physiologically relevant protease targets.

Systemic JIA: new developments in the understanding of the pathophysiology and therapy

Systemic juvenile idiopathic arthritis (sJIA) is a rare, systemic inflammatory disease classified as a subtype of JIA. Besides arthritis, it is characterised by systemic features such as spiking fever, skin rash, hepatosplenomegaly or serositis. It is becoming clear now that abnormalities in the innate immunity (cytokines such as interleukin (IL)-1, IL-6 and IL-18, and neutrophils and monocytes/macrophages rather than lymphocytes) play a major role in the pathogenesis of sJIA, distinguishing it from other JIA subtypes. Another distinctive feature of sJIA is its strong association with macrophage activation syndrome (MAS). Based on this, consensus is emerging that sJIA should be viewed as an autoinflammatory syndrome rather than a classic auto-immune disease. As a consequence of the progression in understanding the underlying mechanisms of sJIA, major changes in the management are evolving. So far, treatment has been based on glucocorticosteroids in combination with disease-modifying drugs such as methotrexate. Recently, remarkable improvement has been observed with IL-1 and IL-6 targeted therapies. These therapies might also change the long-term outcome of this disease. However, controlled trials set up in international collaboration are needed to determine the optimal treatment strategies for all sJIA patients.

Hematopoietic stem cell transplantation in Griscelli syndrome type 2: a single-center report on 10 patients

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment for Griscelli syndrome type 2, an inherited immune disorder causing fatal hemophagocytic lymphohistiocytosis (HLH). Optimal therapeutic modalities are not yet well known. We retrospectively analyzed the outcome for 10 patients who underwent HSCT in a single center between 1996 and 2008. Seven patients (70%) were cured of the primary immune defect (mean follow-up, 5.2 years; range, 0.8-12.0 years), 4 of them without neurologic sequelae. In the 3 deceased patients, death occurred within 110 days of HSCT and was probably due to adverse reaction to HSCT in 2 patients and to HLH relapse in one patient. One patient received 2 transplants because of graft failure. Clinical events included veno-occlusive disease (n = 5), acute (n = 7) or chronic (n = 1) graft-versus-host disease II-III, and Epstein-Barr virus–induced lymphoproliferative disease (n = 2). Of the 7 patients with neurologic involvement before HSCT, 4 survived and 2 presented sequelae. Furthermore, 1 patient lacking neurologic involvement before HSCT developed long-term sequelae. These results demonstrate the efficacy of HSCT in curing the immune disorder but also show that neurologic HLH before HSCT is a major factor, given the neurologic sequelae after otherwise successful HSCT. Additional studies are required to improve treatment.

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

Novel function of perforin in negatively regulating CD4(+) T cell activation by affecting calcium signaling

Perforin is a pore-forming protein engaged mainly in mediating target T cell death and is employed by cytotoxic T lymphocytes (CTLs) and natural killer cells. However, whether it also plays a role in conventional CD4(+) T cell function remains unclear. Here we report that in perforin-deficient (PKO) mice, CD4(+) T cells are hyperproliferative in response to T cell receptor (TCR) stimulation. This feature of hyperproliferation is accompanied by the enhancement both in cell division and in IL-2 secretion. It seems that the perforin deficiency does not influence T cell development in thymus spleen and lymph node. In vivo, perforin deficiency results in increased antigen-specific T cell proliferation and antibody production. Furthermore, PKO mice are more susceptible to experimental autoimmune uveitis. To address the molecular mechanism, we found that after TCR stimulation, CD4(+) T cells from PKO mice display an increased intracellular calcium flux and subsequently enhance activation of transcription factor NFAT1. Our results indicate that perforin plays a negative role in regulating CD4(+) T cell activation and immune response by affecting TCR-dependent Ca(2+) signaling.

Combination of two fiber-mutant adenovirus vectors, one encoding the chemokine FKN and another encoding cytokine interleukin 12, elicits notably enhanced anti-tumor responses

For achieving optimal cancer immunotherapy, it is anticipated that both the activation and infiltration of immune cells into tumor are indispensable. In the present study, fiber-mutant adenovirus vectors (Ad) encoding chemokine FKN, (AdRGD-FKN), and cytokine interleukin 12, (AdRGD-IL-12), were constructed. The in vivo gene expression of AdRGD was confirmed and the combination of both FKN and IL-12 encoding Ad elicited synergistic anti-tumor activity in ovarian carcinoma, which induced tumor regression in all tumor-bearing mice, while using FKN alone did not show notable tumor-suppressive effect. The treatment with both IL-12 and FKN induced long-term specific immunity against OV-HM tumors in tumor-rejected mice. The results of immunohistochemical staining for CD3+ and perforin-positive cells suggested that the failure of using FKN alone was because of the inactivation of infiltrated immune cells. In contrast, cotransduction with IL-12 and FKN could induce more activated tumor-infiltrating immune cells than that transducted with FKN or IL-12 alone. The results indicated that using both chemokine and cytokine might be a powerful tool and a promising way for effective cancer immunotherapy.

Early diagnostic and prognostic significance of a specific Th1/Th2 cytokine pattern in children with haemophagocytic syndrome

The haemophagocytic syndrome (HPS) is a rare but frequently fatal disorder of immune regulation caused by hypercytokinemia. Using cytometric bead array technique, the serum T-helper cell type 1 (Th1) and 2 (Th2) cytokines including interferon-gamma (IFN-gamma), tumour necrosis factor (TNF), interleukin (IL)-10, IL-6, IL-4 and IL-2 were determined in 24 children with de novo HPS and 87 children as control. The median levels of serum IFN-gamma, IL-10 and IL-6 in the acute phase of HPS were 901.7, 879.0 and 63.8 pg/ml, respectively, significantly higher than those after remission, and in the healthy volunteers and patients with viral infection. IL-4 was slightly elevated while IL-2 and TNF were within normal range in acute phase. Patients with bacterial sepsis showed an extremely high level of IL-6 and moderate level of IL-10, whereas IFN-gamma was only slightly elevated. Five patients were diagnosed with HPS according to the Th1/Th2 cytokine pattern 3-13 d earlier than they fulfilled the relevant diagnostic criteria. IL-10 level >2000 pg/ml was an unfavorable prognostic factor for HPS treatment response (P = 0.033) and outcome (P = 0.009). We conclude that the significant increase of IFN-gamma and IL-10 and a slightly increased level of IL-6 is an early, specific and prognostic cytokine pattern for childhood HPS.

Molecular cloning and responsive expression of macrophage expressed gene from small abalone Haliotis diversicolor supertexta

The complete cDNA sequence of macrophage expressed gene (saMpeg1), a perforin-like molecule, was isolated from small abalone (Haliotis diversicolor supertexta) by homology cloning and rapid amplification of cDNA ends (RACE). The full-length cDNA of saMpeg1 was 2781 bp, consisting of a 5'-terminal untranslated region (UTR) of 252 bp, a 3'-terminal UTR of 342 bp with a signal sequence TAA and a poly (A) tail, and an open reading frame of 2184 bp. The deduced protein (saMpeg1) was composed of 728 amino acids, and contains the cytolytic "helix-turn-helix" domain of perforin (residues 171-218), of which the alpha-helices are amphipathic as are those of perforin. A putative single transmembrane domain is located at residues 667-689, and a modified furin cleavage site (KRRRK; residues 689-693) immediately follows. The result of real time quantitative PCR showed that saMpeg1 was highly expressed at 8h and 96 h post-injection of the Gram-negative bacterium Vibrio parahaemolyticus, but there was no change after TBT exposure. The structural similarity to mammalian perforin and the different gene expression level to bacterial infection and TBT exposure suggest that saMpeg1 may play a role in the immune response against microorganisms in small abalone.

Perforin gene mutations in patients with acquired aplastic anemia

Perforin is a cytolytic protein expressed mainly in activated cytotoxic lymphocytes and natural killer cells. Inherited perforin mutations account for 20% to 40% of familial hemophagocytic lymphohistiocytosis, a fatal disease of early childhood characterized by the absence of functional perforin. Aplastic anemia, the paradigm of immune-mediated bone marrow failure syndromes, is characterized by hematopoietic stem cell destruction by activated T cells and Th1 cytokines. We examined whether mutations in the perforin gene occurred in acquired aplastic anemia. Three nonsynonymous PRF1 mutations among 5 unrelated patients were observed. Four of 5 patients with the mutations showed some hemophagocytosis in the bone marrow at diagnosis. Perforin protein levels in these patients were very low or absent, and perforin granules were completely absent. Natural killer (NK) cell cytotoxicity from these patients was significantly decreased. Our data suggest that PRF1 genetic alterations help explain the aberrant proliferation and activation of cytotoxic T cells and may represent genetic risk factors for bone marrow failure.

Regulating secretory lysosomes

Secretory lysosomes are lysosomes which are capable of undergoing regulated secretion in response to external stimuli. Many cells of the immune system use secretory lysosomes to release proteins involved in their specialised effector mechanisms. Precisely how lysosomal secretion is regulated in each of these cell types is now the study of much research as these mechanisms control the ability of each of these cells to function. Studies on a number of human genetic diseases have identified some key proteins in controlling secretory lysosome release, and now many interacting partners have been identified. The different regulatory components seem to vary from one cell type to another, providing a multitude of ways for fine tuning the release of secretory lysosomes.

Pediatric hemophagocytic syndromes: a diagnostic and therapeutic challenge

Pediatric hemophagocytic syndrome (HS) is a severe and often fatal clinical disorder. This syndrome is frequently unrecognized, and thus, affected children may receive suboptimal management, leading to an increase in mortality. The purpose of this review is to provide a clinical guide to (1) the recognition of HS based on clinical, biologic, and pathologic features; (2) the identification of the primary cause of HS in a given affected child; and (3) the initiation of effective treatment in a timely manner.

Peripheral blood cytotoxic lymphocyte gene transcript levels differ in patients with long-term type 1 diabetes compared to normal controls

The purpose of this study was to compare mRNA levels of the cytotoxic lymphocyte (CL) gene products: granzyme B (GB), perforin (P), and fas ligand (FasL) in patients with long-term type 1 diabetes and healthy controls. The objective was to utilize this information to follow patients as they undergo islet cell transplantation at our center and to determine if changes in CL gene transcript levels correlate with graft status. We have measured mRNA levels for CL genes in peripheral blood samples from 65 long-term (>5 years) type 1 diabetes patients and 29 healthy controls. Total RNA was extracted from EDTA anticoagulated peripheral blood samples and reverse transcribed into first-strand cDNA using SuperScript II reverse Transcriptase. Quantitative, real-time PCR was utilized to determine CL gene transcript levels. mRNA levels of P and FasL genes were found to be significantly lower for patients with type 1 diabetes compared to normal controls (p < 0.05). However, there was no significant difference for GB mRNA levels between patients and controls (p > 0.05). The decreased expression of P and FasL in patients with long-term type 1 diabetes might contribute to the inability to maintain normal levels of peripheral tolerance, which is essential for protection from autoimmune disease.

Effect of the CTL proliferation program on virus dynamics

Experiments have established that CTLs do not require continuous antigenic stimulation for expansion. Instead, responses develop by a process of programmed proliferation which involves approximately 7-10 antigen-independent cell divisions, the generation of effector cells and the differentiation into memory cells. The effect of this program on the infection dynamics and the advantages gained by the program have, however, not been explored yet. We investigate this with mathematical models. We find that more programmed divisions can make virus clearance more efficient because CTL division continues to occur independent from antigenic stimulation when virus load drops to low levels. This results in stronger effector activity at low virus loads, and in a higher chance of virus extinction. On the other hand, the more programmed divisions occur, the less efficient the response is at preventing high acute virus loads and thus acute symptoms. The reason is that the programmed divisions are independent from antigenic stimulation, and an increase in virus load does not speed up the rate of CTL expansion. We hypothesize that the 7-10 programmed divisions observed in vivo represent an optimal solution to this trade-off which maximizes the chances to clear, while preventing excessive acute pathology. If the CTLs fail to clear the virus, however, we find that the properties of the programmed proliferation model are very similar to those derived from models which assume continuous antigenic stimulation. We discuss these results in the context of data from murine virus infections and explore implications for virus dynamics in CD4 helper-deficient hosts.

Macrophage activation syndrome in a child with systemic juvenile rheumatoid arthritis

Macrophage activation syndrome (MAS) is a rare and potentially fatal complication of rheumatic disorders in children. We describe a 13-month-old boy in whom MAS developed as a complication of systemic juvenile rheumatoid arthritis (S-JRA). He suffered from fever and generalized rash followed by multiple joints swelling for four months before admission. Physical examination revealed cervical lymphadenopathy and hepatosplenomegaly. Laboratory findings were: abnormal liver enzymes, increased triglyceride and ferritin levels, coagulopathies resembling disseminated intravascular coagulation, anemia and thrombocytopenia. Hyperplasia of hemophagocytic macrophages was remarkable in his bone marrow. Methylprednisolone and cyclosporin therapy resulted in clinical and laboratory improvements. This is the third case of MAS associated with S-JRA in Koreans, and the first one, in which hemophagocytic macrophages were proven in bone marrow.

Subtyping of natural killer cell cytotoxicity deficiencies in haemophagocytic lymphohistocytosis provides therapeutic guidance

The familial form of haemophagocytic lymphohistiocytosis (HLH) is a fatal disease, with allogeneic stem cell transplantation (SCT) being the only curative treatment. In contrast, patients with secondary (infection-associated) HLH usually do not require SCT. Since it often is difficult to distinguish primary and secondary HLH, we wanted to identify a tool that provides guidance on whether SCT is required. The clinical outcome of 65 HLH patients was analysed in relation to the recently reported four types of defects in natural killer (NK)-cell cytotoxicity in HLH. None (0%) of the 36 patients with NK-cell deficiency type 3 attained a sustained (1-year) remission after stopping therapy without receiving SCT, in contrast to 45% (13/29) non-type 3 patients (P < 0.001). Most type 3 patients (22/36) underwent SCT (14/22, 64% are alive), whereas 11 of 14 that did not receive SCT died, and the three others had received HLH-therapy during the last year of follow-up. Of 54 patients analysed for perforin expression and/or mutation, the five with perforin deficiency were all type 3 patients. The data suggests that HLH patients with NK-cell deficiency type 3 will probably require SCT to survive. Thus, NK-cell deficiency classification may provide valuable guidance in judging whether an HLH-patient needs SCT.

Does systemic-onset juvenile idiopathic arthritis belong under juvenile idiopathic arthritis?

'Science is the systematic classification of experience' George Henry Lewes (1817-78), English philosopher, critic, dramatist, scientist. Juvenile idiopathic arthritis (JIA) is prevalent in about 1 in 1000 children. The earliest formal description of this disease was by Sir George Frederick Still in 1897. This work was done when he was a registrar at the Hospital for Sick Children, Great Ormond Street, London. In this initial description of 19 patients he identified three patterns of arthritis, one of which came to be known later as Still's disease [now known as systemic-onset juvenile idiopathic arthritis (SoJIA)]. Over the next few decades it came to be appreciated that one form of arthritis in children is very different and dominated by the presence of systemic manifestations. Over the last two decades several paediatric rheumatologists have come together to classify juvenile arthritis for purposes of better disease identification and research. All along, the systemic form of juvenile arthritis was always recognized as belonging to a distinct group; in fact for several decades (and even now in some countries) the systemic form of juvenile arthritis was referred to as Still's disease. In this article we will attempt to highlight the reasons why we feel that SoJIA is perhaps not best retained in the company of JIA.

Does programmed CTL proliferation optimize virus control?

CD8 T-cell or cytotoxic T-lymphocyte responses develop through an antigen-independent proliferation and differentiation program. This is in contrast to the previous thinking, which was that continuous antigenic stimulation was required. This Opinion discusses why nature has chosen the proliferation program and how it compares to continuous stimulation. Although the two mechanisms should not lead to significantly different dynamics during chronic infection, they do make a difference in acute infection. We argue that programmed proliferation is better at clearance, whereas continuous stimulation is better at limiting acute symptoms. The 7-10 programmed cell divisions observed in vivo might be an optimization of this trade-off. We also discuss the conditions under which the program does or does not require CD4 T-cell help for clearance.

Impaired Cytolytic Activity in Calreticulin-Deficient CTLs

Calreticulin is an endoplasmic reticulum-resident chaperone that is stored in the cytotoxic granules of CTLs and NK cells and is released with granzymes and perforin upon recognition of target cells. To investigate the role of calreticulin in CTL-mediated killing, we generated CTL lines from crt(+/+) and crt(-/-) mice expressing a constitutively active form of calcineurin in the heart. Crt(-/-) CTLs showed reduced cytotoxic activity toward allogeneic target cells despite normal production, intracellular localization, and activity of granzymes and despite perforin overexpression. Comparable or higher amounts of granzymes were degranulated by crt(-/-) cells in response to immobilized anti-CD3 Abs, indicating that calreticulin is dispensable for the signal transduction that leads to granule exocytosis. The ability to form conjugates with target cells was affected in the crt(-/-) CTLs, explaining the observed reduction in cytotoxicity. Conjugate formation and cytotoxicity were completely restored by treatments that facilitate recognition and contact with target cells, a prerequisite for degranulation and killing. Therefore, we conclude that calreticulin is dispensable for the cytolytic activity of granzymes and perforin, but it is required for efficient CTL-target cell interaction and for the formation of the death synapse.

The integration of conventional and unconventional T cells that characterizes cell-mediated responses

This review builds on evidence that cell-mediated immune responses to bacteria, viruses, parasites, and tumors are an integration of conventional and unconventional T-cell activities. Whereas conventional T cells provide clonal antigen-specific responses, unconventional T cells profoundly regulate conventional T cells, often suppressing their activities such that immunopathology is limited. By extrapolation, immunopathologies and inflammatory diseases may reflect defects in regulation by unconventional T cells. To explore the function of unconventional T cells, several extensive gene expression analyses have been undertaken. These studies are reviewed in some detail, with emphasis on the mechanisms by which unconventional T cells may exert their regulatory functions. Highlighting the fundamental nature of T-cell integration, we also review emerging data that the development of conventional and unconventional T cells is also highly integrated.

Natural killer cell dysfunction is a distinguishing feature of systemic onset juvenile rheumatoid arthritis and macrophage activation syndrome

Macrophage activation syndrome (MAS) has been reported in association with many rheumatic diseases, most commonly in systemic juvenile rheumatoid arthritis (sJRA). Clinically, MAS is similar to hemophagocytic lymphohistiocytosis (HLH), a genetic disorder with absent or depressed natural killer (NK) function. We have previously reported that, as in HLH, patients with MAS have profoundly decreased NK activity, suggesting that this abnormality might be relevant to the pathogenesis of the syndrome. Here we examined the extent of NK dysfunction across the spectrum of diseases that comprise juvenile rheumatoid arthritis (JRA). Peripheral blood mononuclear cells (PBMC) were collected from patients with pauciarticular (n = 4), polyarticular (n = 16), and systemic (n = 20) forms of JRA. NK cytolytic activity was measured after co-incubation of PBMC with the NK-sensitive K562 cell line. NK cells (CD56⁺/T cell receptor [TCR]-αβ^-), NK T cells (CD56⁺/TCR-αβ⁺), and CD8⁺ T cells were also assessed for perforin and granzyme B expression by flow cytometry. Overall, NK cytolytic activity was significantly lower in patients with sJRA than in other JRA patients and controls. In a subgroup of patients with predominantly sJRA, NK cell activity was profoundly decreased: in 10 of 20 patients with sJRA and in only 1 of 20 patients with other JRA, levels of NK activity were below two standard deviations of pediatric controls (P = 0.002). Some decrease in perforin expression in NK cells and cytotoxic T lymphocytes was seen in patients within each of the JRA groups with no statistically significant differences. There was a profound decrease in the proportion of circulating CD56^bright NK cells in three sJRA patients, a pattern similar to that previously observed in MAS and HLH. In conclusion, a subgroup of patients with JRA who have not yet had an episode of MAS showed decreased NK function and an absence of circulating CD56^bright population, similar to the abnormalities observed in patients with MAS and HLH. This phenomenon was particularly common in the systemic form of JRA, a clinical entity strongly associated with MAS.

Immune mechanism of drug hypersensitivity

Drug hypersensitivity reactions can lead to a great variety of different diseases. The main cause is a specific interaction of antibodies or T cells with a drug. In addition to the hapten concept, some drugs can bind directly to T-cell receptors and stimulate them. Based on recent investigation on different exanthemas, an extended classification of the Gell and Coombs type IV reaction is proposed.

A20 protects endothelial cells from TNF-, Fas-, and NK-mediated cell death by inhibiting caspase 8 activation

A20 is a stress response gene in endothelial cells (ECs). A20 serves a dual cytoprotective function, protecting from tumor necrosis factor (TNF)-mediated apoptosis and inhibiting inflammation via blockade of the transcription factor nuclear factor-kappaB (NF-kappaB). In this study, we evaluated the molecular basis of the cytoprotective function of A20 in EC cultures and questioned whether its protective effect extends beyond TNF to other apoptotic and necrotic stimuli. Our data demonstrate that A20 targets the TNF apoptotic pathway by inhibiting proteolytic cleavage of apical caspases 8 and 2, executioner caspases 3 and 6, Bid cleavage, and release of cytochrome c, thus preserving mitochondrion integrity. A20 also protects from Fas/CD95 and significantly blunts natural killer cell-mediated EC apoptosis by inhibiting caspase 8 activation. In addition to protecting ECs from apoptotic stimuli, A20 safeguards ECs from complement-mediated necrosis. These data demonstrate, for the first time, that the cytoprotective effect of A20 in ECs is not limited to TNF-triggered apoptosis. Rather, A20 affords broad EC protective functions by effectively shutting down cell death pathways initiated by inflammatory and immune offenders.

Increased interleukin-18 expression in bone marrow of a patient with systemic juvenile idiopathic arthritis and unrecognized macrophage-activation syndrome

The aberrant induction of proinflammatory cytokines is considered to be crucial in the pathogenesis of systemic juvenile idiopathic arthritis and adult-onset Still's disease. Interleukin-18 (IL-18) in particular has been reported to be a candidate for the key cytokine in both diseases; however, the origin of IL-18 is unclear. To clarify the origin, we investigated specimens from various organs obtained during autopsy of a child with systemic JIA and macrophage activation syndrome, using immunohistochemical staining. Our results showed a high number of cells expressing IL-18 in the bone marrow but not in the other organs. This finding suggests that bone marrow is the origin of increased serum IL-18 and raises the possibility that other proinflammatory cytokines are also induced by IL-18 in bone marrow in this disease. Bone marrow may be an essential organ in the pathogenesis of systemic JIA.

Linking albinism and immunity: the secrets of secretory lysosomes

Lysosomes are membrane-bound organelles that are found in all mammalian cells and contain hydrolases and lipases required for protein and membrane degradation. In many cells of the immune system, lysosomes also contain secretory proteins that can be released by regulated exocytosis in response to an external stimulus, providing different cell types with a wide range of effector functions. Melanosomes also use a lysosome-related organelle to secrete melanin for pigmentation. Links between albinism and immunity in patients have uncovered a number of key proteins required for lysosomal secretion and have revealed a versatile secretory mechanism that can be fine-tuned by distinct interactions in different cell types.

A perforin-like protein from a marine mollusk

Abalone (gastropod mollusks) express a protein, abMpeg1, which is a homolog of two mammalian proteins that share homology with mammalian perforin, a cytolytic and immune-regulatory protein of lymphocytes. One of the mammalian proteins, Mpeg1, is expressed in mature macrophage and prion-infected mouse brains, while the other, Epcs50, is expressed in ectoplacental cone cells of the invading placenta. Although the functions of these three proteins remain unknown, their structural similarity to mammalian perforin suggests that they may be involved in cell killing, the inflammatory response or tissue invasion. Consistent with these proposed functions, the Mpeg1 gene family shows the signature of positive Darwinian selection (adaptive evolution). The perforin-homology domain of abMpeg1 contains the cytolytic "helix-turn-helix" domain of perforin, supporting the idea that abMpeg1 is a cytolytic protein of the abalone innate immune system. The alpha-helices of abMpeg1 are amphipathic as are those of perforin. The conservation among abMpeg1, mammalian Mpeg1, and Epcs50 shows that Mpeg1 proteins represent a novel, ancient protein family of probable immunological function.

Specific Alteration of Peripheral Cytotoxic Cell Perforin Expression in Alcoholic Patients: A Possible Role in Alcohol-Related Diseases

BACKGROUND

The association between chronic alcohol consumption and an increasing risk of infectious and neoplastic disease is related to an impairment of cellular immunity. However, studies of the number and activity of lymphocyte subsets show highly variable results. The aim of this study was to assess the expression of perforin, one of the main molecular agents of T and natural killer (NK) cell-mediated cytotoxicity, in alcoholic patients without cirrhosis.

METHODS

Eighteen patients with chronic alcoholism were prospectively included and compared with 18 age- and sex-matched healthy volunteers. Signs of hepatic insufficiency or portal hypertension, viral co-infection, other serious medical illness, and immune-related medications were exclusion criteria. Lymphocyte phenotype was assessed, and perforin expression was analyzed by flow cytometry in CD3+CD56+ T cells and NK cells. Granzyme synthesis was also evaluated in 11 of the 18 patients and compared with that of 11 age- and sex-matched controls.

RESULTS

The mean number of white blood cells and lymphocytes was not different between the controls and alcoholic patients, whereas the mean number of NK cells was significantly decreased in alcoholic patients (110 +/- 79/mm3 versus 271 +/- 192/mm3; p < 0.03). Perforin expression in T CD3+/CD56+ and in NK cells was significantly decreased in alcoholic patients compared with controls: 16 +/- 3% vs. 36 +/- 4% (p < 0.03) and 65 +/- 15% vs. 78 +/- 9% (p = 0.04), respectively. The percentage of cells expressing granzyme was similar in both groups.

CONCLUSIONS

A decrease in perforin expression by cytotoxic cells could be a major factor in explaining the physiopathologic mechanisms of several alcohol-associated diseases.

Macrophage activation syndrome and reactive hemophagocytic lymphohistiocytosis: the same entities?

PURPOSE OF THE REVIEW

One of the most perplexing features of systemic-onset juvenile rheumatoid arthritis is the association with macrophage activation syndrome, a life-threatening complication caused by excessive activation and proliferation of T cells and macrophages. The main purpose of the review is to summarize current understanding of the relation between macrophage activation syndrome and other clinically similar hemophagocytic disorders.

RECENT FINDINGS

Clinically, macrophage activation syndrome has strong similarities with familial and virus-associated reactive hemophagocytic lymphohistiocytosis. The better understood familial hemophagocytic lymphohistiocytosis is a constellation of rare, autosomal recessive immune disorders. The most consistent immunologic abnormalities in patients with familial hemophagocytic lymphohistiocytosis are decreased natural killer and cytotoxic cell functions. In approximately one third of familial hemophagocytic lymphohistiocytosis patients, these immunologic abnormalities are secondary to mutations in the gene encoding perforin, a protein that mediates cytotoxic activity of natural killer and cytotoxic CD8+ T cells. Several recent studies have suggested that profoundly depressed natural killer cell activity and abnormal levels of perforin expression may be a feature of macrophage activation syndrome in systemic-onset juvenile rheumatoid arthritis as well. Although it has been proposed that in both hemophagocytic lymphohistiocytosis and macrophage activation syndrome, natural killer and cytotoxic cell dysfunction may lead to inadequate control of cellular immune responses, the exact nature of such dysregulation and the relation between macrophage activation syndrome and hemophagocytic lymphohistiocytosis still remain to be determined.

Leishmania lipophosphoglycan (LPG) activates NK cells through toll-like receptor-2

Toll-like receptors (TLRs) mediate the cellular response to conserved molecular patterns shared by microorganisms. We report that TLR-2 on human NK cells is upregulated and stimulated by Leishmania major lipophosphoglycan (LPG), a phosphoglycan belonging to a family of unique Leishmania glycoconjugates. We found that purified L. major LPG upregulates both mRNA and the membrane expression of TLR-2 in NK cells. Additionally, IFN-gamma and TNF-alpha production and nuclear translocation of NF-kappaB was enhanced. The activation effect was more intense with LPG purified from infectious metacyclic parasites than from noninfectious procyclic Leishmania. Since the difference between the molecules derived from these two stages of the parasite growth cycle lies exclusively in the number of phosphosaccharide repeat domains and in the composition of glycan side chains that branch off these domains, we propose that TLR-2 possibly distinguishes between phosphorylated glycan repeats on LPG molecules. The effect of LPG on cytokine production and on membrane expression of TLR-2 could be blocked with F(ab')2 fragments of the mAb against LPG (WIC 79.3). Confocal microscopy demonstrated the co-localization of LPG and TLR-2 on the NK cell membrane. Binding of LPG to TLR-2 in NK cells was demonstrated by immunoprecipitations done with anti-TLR-2 and anti-LPG mAb followed by immunoblotting with anti-LPG and anti-TLR-2, respectively. Both antibodies recognized the immune complexes. These results suggest that NK cells are capable of recognition of, and activation by, Leishmania LPG through TLR-2, enabling them to participate autonomously in the innate immune system and thereby increasing the effective destruction of the parasite.

Characteristic perforin gene mutations of haemophagocytic lymphohistiocytosis patients in Japan

Perforin gene (PRF1) mutations appear to occur in about 30% of patients with haemophagocytic lymphohistiocytosis (HLH). We tested perforin expression and gene mutations in 14 HLH patients and six patients with Epstein-Barr virus-associated HLH (EBV-HLH) in Japan. Five of the 14 HLH patients had perforin abnormalities. The presence of PRF1 genetic abnormality correlated well with the lack of perforin expression as determined by flow cytometry. Sequencing showed that four patients had a compound heterozygous mutation while the fifth patient had a homozygous mutation. Three of the mutations we detected were novel. In contrast, none of the six EBV-HLH patients showed perforin abnormalities. Our data, combined with the PRF1 mutations in three previously reported Japanese patients, suggest that the 1090-1091delCT and 207delC mutations of the perforin gene are frequently present in Japanese HLH patients (62.5% and 37.5% respectively). Examination of the geographical origins of the ancestors in the perforin-mutant HLH patients revealed that they mostly came from the Western part of Japan, suggesting that the present-day cases may largely derive from a common ancestor.

Delivering the kiss of death

Cytotoxic T lymphocytes and natural killer cells kill their targets by secreting specialized granules that contain potent cytotoxic molecules. Through the study of rare immunodeficiency diseases in which this granule pathway of killing is impaired, proteins such as Rab27a have been identified as components of the secretory machinery of these killer cells. Recent evidence suggests that the destruction of activated lymphocytes through granule-mediated killing may be an important mechanism of immunological homeostasis. Although the process by which this occurs is not yet known, it is possible that events taking place at the immunological synapse may render the killer cell susceptible to fratricidal attack by other killer cells.

CD44 variant isoform v10 is expressed on tumor-infiltrating lymphocytes and mediates hyaluronan-independent heterotypic cell-cell adhesion to melanoma cells

CD44 is a family of cell-surface receptors on human lymphocytes that act as co-stimulatory molecules leading to the induction of effector functions in T cells. We have analyzed primary cutaneous malignant melanomas with clinical and histologic signs of tumor regression using immunohistochemistry and observed the predominant expression of the CD44 variant isoform v10 on CD3 CD4/CD8 co-expressing tumor-infiltrating lymphocytes (TIL). We further analyzed the role of CD44v10 in adhesion of lymphocytes to human melanoma cells. In contrast to CD44- lymphatic cells, CD44v10+ lymphatic cells strongly bound to cultured human melanoma cells and to frozen tissue samples of melanomas. Antibody blocking studies revealed a hyaluronan-, integrin-, and selectin-independent pathway of adhesion. Furthermore, CD44v10+ lymphatic cells exhibited significantly higher invasiveness in three-dimensional collagen matrices as compared with CD44H+ and CD44-negative lymphocytes. These results indicate that expression of CD44v10 on TIL may mediate adhesion to melanoma cells and result in gain of novel invasive properties.

Natural killer cell dysfunction in patients with systemic-onset juvenile rheumatoid arthritis and macrophage activation syndrome

OBJECTIVES

To assess natural killer (NK) and cytotoxic functions in patients with systemic-onset juvenile rheumatoid arthrithis (soJRA) complicated by macrophage activation syndrome (MAS).

METHODS

NK cells (CD56+/TCRalphabeta-), NK T cells (CD56+/TCRalphabeta+) and CD8+ cells were assessed for perforin expression by flow cytometry. NK cytotoxic activity was measured after coincubation of mononuclear cells with an NK-sensitive K562 cell line.

RESULTS

Two major patterns of immunologic abnormalities were detected. Four of 7 patients had decreased NK activity, low NK cell numbers, and mildly increased levels of perforin expression in CD8+ and CD56+ cytotoxic cells. Three remaining patients with MAS, however, had decreased NK activity associated with low levels of perforin expression in all cytotoxic cell populations, a pattern indistinguishable from that in carriers of perforin-deficient familial hemophagocytic lymphohistiocytosis. Remarkably, two of these patients had previous episodes of MAS.

CONCLUSIONS

NK dysfunction is an immunologic abnormality common to both familial hemophagocytic lymphohistiocytosis and MAS of soJRA. The extent of NK cell abnormalities in soJRA needs to be further investigated.

Perforin is required for innate and adaptive immunity induced by heat shock protein gp96

Tumor-secreted gp96-Ig is highly immunogenic and triggers CD8 T cell-mediated tumor rejection. In vivo secreted gp96-Ig and gp96-myc cause NK activation and clonal expansion of specific CD8(+) CTL in wild-type and in Fas-ligand-deficient (gld) mice but not in perforin- (PKO) or IFN-gamma-deficient (GKO) mice. Transfer of perforin-competent NK cells restores the ability of PKO mice to clonally expand CD8 CTL in response to gp96-Ig. The data demonstrate an essential role for perforin-mediated functions in the activation of innate and adaptive immunity by heat shock protein gp96-peptide complexes. Crosspresentation of antigens by heat shock proteins seems to require a perforin-dependent positive feedback loop between NK and DC for both sustained NK activation and clonal CTL expansion. The studies also explain how depressed NK activity in patients with tumors or after viral infections could diminish CTL responses.

Searching for interferon-induced genes that inhibit hepatitis B virus replication in transgenic mouse hepatocytes

We have previously shown that alpha/beta interferon (IFN-alpha/beta) and IFN-gamma inhibit hepatitis B virus (HBV) replication noncytopathically in the livers of HBV transgenic mice and in hepatocyte cell lines derived from these mice. The present study was designed to identify transcriptionally controlled hepatocellular genes that are tightly associated with the inhibition of HBV replication and that might, therefore, mediate the antiviral effect of these cytokines. Twenty-nine genes were identified, many of which have known or potential antiviral activity. Notably, multiple components of the immunoproteasome and ubiquitin-like proteins were strongly induced by both IFN-alpha/beta and IFN-gamma, as were a number of GTP-binding proteins, including GTPases with known antiviral activity, chemokines, signaling molecules, and miscellaneous genes associated with antigen processing, DNA-binding, or cochaperone activity and several expressed sequence tags. The results suggest that one or more members of this relatively small subset of genes may mediate the antiviral effect of IFN-alpha/beta and IFN-gamma against HBV. We have already exploited this information by demonstrating that the antiviral activity of IFN-alpha/beta and IFN-gamma is proteasome dependent.