Human lupus inclusions and interferon

Interferon autoantibodies as signals of a sick thymus

Type I interferons (IFN-I) are key immune messenger molecules that play an important role in viral defense. They act as a bridge between microbe sensing, immune function magnitude, and adaptive immunity to fight infections, and they must therefore be tightly regulated. It has become increasingly evident that thymic irregularities and mutations in immune genes affecting thymic tolerance can lead to the production of IFN-I autoantibodies (autoAbs). Whether these biomarkers affect the immune system or tissue integrity of the host is still controversial, but new data show that IFN-I autoAbs may increase susceptibility to severe disease caused by certain viruses, including SARS-CoV-2, herpes zoster, and varicella pneumonia. In this article, we will elaborate on disorders that have been identified with IFN-I autoAbs, discuss models of how tolerance to IFN-Is is lost, and explain the consequences for the host.

The Role of the Oxidative State and Innate Immunity Mediated by TLR7 and TLR9 in Lupus Nephritis

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) and is considered one of the leading causes of mortality. Multiple immunological pathways are involved in the pathogenesis of SLE, which makes it imperative to deepen our knowledge about this disease's immune-pathological complexity and explore new therapeutic targets. Since an altered redox state contributes to immune system dysregulation, this document briefly addresses the roles of oxidative stress (OS), oxidative DNA damage, antioxidant enzymes, mitochondrial function, and mitophagy in SLE and LN. Although adaptive immunity's participation in the development of autoimmunity is undeniable, increasing data emphasize the importance of innate immunity elements, particularly the Toll-like receptors (TLRs) that recognize nucleic acid ligands, in inflammatory and autoimmune diseases. Here, we discuss the intriguing roles of TLR7 and TLR9 in developing SLE and LN. Also included are the essential characteristics of conventional treatments and some other novel and little-explored alternatives that offer options to improve renal function in LN.

STING-Mediated Lung Inflammation and Beyond

Mendelian autoinflammatory diseases characterized by constitutive activation of the type I interferon pathway, the so-called type I interferonopathies, constitute a rapidly expanding group of inborn errors of immunity. Among the type I interferonopathies, STING-associated vasculopathy with onset in infancy (SAVI) and COPA syndrome were described in the last 6 years, both manifesting a major inflammatory lung component associated with significant morbidity and increased mortality. There is striking clinical and histopathological overlap between SAVI and COPA syndrome, although distinct features are also present. Of note, there is a remarkably high frequency of clinical non-penetrance among individuals harboring pathogenic COPA mutations. SAVI is caused by, principally heterozygous, gain-of-function mutations in STING1 (previously referred to as TMEM173) encoding STING, a key adaptor of the interferon signaling pathway induced by DNA. COPA syndrome results from heterozygous dominant-negative mutations in the coatomer protein subunit alpha, forming part of a complex involved in intracellular cargo protein transport between the Golgi and the endoplasmic reticulum (ER). Of importance, a role for COPA in regulating the trafficking of STING, an ER-resident protein which translocates to the Golgi during the process of its activation, was recently defined, thereby possibly explaining some aspects of the phenotypic overlap between SAVI and COPA syndrome. Here, we review the expanding phenotype of these diseases, highlighting common as well as specific features, and recent advances in our understanding of STING biology that have informed therapeutic decision-making in both conditions. Beyond these rare Mendelian disorders, DNA sensing through STING is likely relevant to the pathology of several diseases associated with lung inflammation, including systemic lupus erythematosus, dermatomyositis, environmental toxin exposure, and viral infection.

[Pathological consequences of excess of interferon in vivo]

In this brief review, the authors present a history of the different aspects of the scientific puzzle leading from pioneer animal studies and astute clinical experimental observations to a mature appreciation of the deleterious role of excess of a type I interferon in human pathology.

Pediatric lupus nephritis

Involvement of the kidneys by lupus nephritis (LN) is one of the most severe clinical manifestations seen in individuals with systemic lupus erythematosus (SLE). LN is more frequent and severe in pediatric patients and has been associated with higher morbidity and mortality rates. This narrative review aimed to describe the general aspects of LN and its particularities when affecting children and adolescents, while focusing on the disease's etiopathogenesis, clinical manifestations, renal tissue alterations, and treatment options.

Type I Interferons in Autoimmune Disease

Type I interferons, which make up the first cytokine family to be described and are the essential mediators of antivirus host defense, have emerged as central elements in the immunopathology of systemic autoimmune diseases, with systemic lupus erythematosus as the prototype. Lessons from investigation of interferon regulation following virus infection can be applied to lupus, with the conclusion that sustained production of type I interferon shifts nearly all components of the immune system toward pathologic functions that result in tissue damage and disease. We review recent data, mainly from studies of patients with systemic lupus erythematosus, that provide new insights into the mechanisms of induction and the immunologic consequences of chronic activation of the type I interferon pathway. Current concepts implicate endogenous nucleic acids, driving both cytosolic sensors and endosomal Toll-like receptors, in interferon pathway activation and suggest targets for development of novel therapeutics that may restore the immune system to health.

Epigenetics in SLE

Purpose of Review

Systemic lupus erythematosus is a severe autoimmune/inflammatory condition of unknown pathophysiology. Though genetic predisposition is essential for disease expression, risk alleles in single genes are usually insufficient to confer disease. Epigenetic dysregulation has been suggested as the missing link between genetic risk and the development of clinically evident disease.

Recent Findings

Over the past decade, epigenetic events moved into the focus of research targeting the molecular pathophysiology of SLE. Epigenetic alteration can be the net result of preceding infections, medication, diet, and/or other environmental influences. While altered DNA methylation and histone modifications had already been established as pathomechanisms, DNA hydroxymethylation was more recently identified as an activating epigenetic mark.

Summary

Defective epigenetic control contributes to uncontrolled cytokine and co-receptor expression, resulting in immune activation and tissue damage in SLE. Epigenetic alterations promise potential as disease biomarkers and/or future therapeutic targets in SLE and other autoimmune/inflammatory conditions.

Ultrastructural Modifications in one Case of Hairy Cell Leukemia during Alpha-Interferon Therapy

There are many reports concerning the morphology of hairy cell leukemia (HCL), but, to our knowledge, there are no data on the ultrastructural modifications of HCL during interferon therapy. The ultrastructural modifications of neoplastic cells In peripheral blood in a case of HCL were investigated before and 2 and 4 months after beginning treatment with human lymphoblastoid alpha-interferon. Before therapy, hairy cells displayed the typical cytoplasmic projections, and 4 % contained ribosome-lamellae complexes (RLC) (the cells contained up to 7 RLC). Two months from the beginning of therapy, hairy cells had shorter projections, RLC had disappeared, and tubuloreticular structures (TRS) had appeared in 2.2 % of the elements. Four months from the beginning of therapy, TRS persisted in 2.3 % of hairy cells, cylindrical confronting cisternae (CCC) appeared in 6.8 % of the cells, and uncommon RLC, in close contact with the rough endoplasmic reticulum and nuclear membrane, were found in 1.5 % of the elements. The cells contained up to 3 RLC. Our data confirm that interferon stimulates the synthesis of TRS and CCC, whereas the reappearance of uncommon forms of RLC could reflect their neosynthesis, possibly related to the interferon therapy. The frequent findings of a close contact between RLC and nuclear membrane support the view that RLC are derived not only from rough endoplasmic reticulum, but also from the nuclear membrane.

Hairy Cell Leukemia: An Ultrastructural Study of Hairy Cells before and after Interferon Therapy

Aims and background

To test the diagnostic relevance of the presence of ribosome-lamellae complexes (RLC) in 18 hairy cell leukemia (HCL) cases, and to correlate clinical response to interferon (IFN) therapy with hairy cell ultrastructural modifications in 5 of these cases.

Methods

Peripheral blood samples of 18 HCL patients were studied by transmission electron microscopy. Five of these patients received IFN treatment and subsequently were evaluated at different intervals for ultrastructural modifications of the peripheral blood.

Results

RLC were observed in 66.66% of our 18 HCL patients, but in less than 1% of all the cases contained in the files (consisting of over 8,000 cases) of our Electron Microscopy Unit. The microvilli disappeared after IFN therapy in the patients who did not display RLC before therapy (2 cases), whereas they were fewer, shortened and blunted, but still evident, in the cases where RLC had been observed before therapy (3 cases). Moreover, in the HCL cases with pre-therapy RLC, neoplastic cells still synthesized RLC after IFN treatment, but their morphologic aspect was immature.

Conclusions

Our study suggests that: 1) the presence of RLC, when associated to the hairy aspect of the cells, has considerable diagnostic value even though RLC are observed in other rare neoplastic and non-neoplastic conditions; 2) HCL cases with pre-therapy RLC exhibited a morphologic response to IFN therapy different from that of cases without pre-therapy RLC; 3) the quantitative and qualitative modifications of RLC following IFN treatment, as yet unexplained, are probably related to IFN action, in line with a previous report.

Tubuloreticular Inclusions in the Absence of Systemic Lupus Erythematosus and HIV Infection: A Report of Three Pediatric Cases

Tubuloreticular inclusions (TRIs) are subcellular structures located within the cisternae of endoplasmic reticulum. Formation of TRIs has been linked to the exposure of excess interferon (IFN), either from endogenous or exogenous sources. In renal disease, TRIs have been most commonly associated with systemic lupus erythematosus (SLE), and human immunodeficiency virus-associated nephropathy (HIVAN). Case reports of patients with renal biopsies showing TRIs without underlying SLE or HIV are infrequent in adults, and to our knowledge none have been reported in children. We report 3 pediatric cases in which the renal biopsy showed TRIs on electron microscopy without underlying SLE or HIV infection. The first patient presented at 2 years of age with nephrotic syndrome and renal failure. His renal biopsy revealed focal segmental glomerulosclerosis and TRIs. The second patient presented at 6 months of age with infantile nephrotic syndrome, and his renal biopsy revealed membranous glomerulopathy and TRIs. The last patient presented at 4 years of age with acute kidney injury of unclear etiology leading to chronic kidney disease. Her biopsy revealed acute and chronic tubulointerstitial nephritis with TRIs. Despite extensive evaluation in all 3 patients, including testing for HIV infection and SLE, we could not identify an underlying etiology to explain the presence of TRIs. In conclusion, renal biopsy with TRIs in the absence of underling SLE and HIV remains obscure. We propose a possible role for excess IFN triggered by an abnormal immune response to common viral infections in the formation of TRIs and renal injury.

DNA methylation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease facilitated by aberrant immune responses directed against cells and tissues, resulting in inflammation and organ damage. In the majority of patients, genetic predisposition is accompanied by additional factors conferring disease expression. While the exact molecular mechanisms remain elusive, epigenetic alterations in immune cells have been demonstrated to play a key role in disease pathogenesis through the dysregulation of gene expression. Since epigenetic marks are dynamic, allowing cells and tissues to differentiate and adjust, they can be influenced by environmental factors and also be targeted in therapeutic interventions. Here, we summarize reports on DNA methylation patterns in SLE, underlying molecular defects and their effect on immune cell function. We discuss the potential of DNA methylation as biomarker or therapeutic target in SLE.

Immunopathology of lupus nephritis

When patients with systemic lupus erythematosus (SLE) present with urinary abnormalities, a renal biopsy is usually needed to rule out or confirm lupus nephritis. Renal biopsy is also needed to define the type of renal manifestation as different entities are associated with different outcomes; hence, renal biopsy results shape lupus management. But why does lupus nephritis come in different shapes? Why do patients with SLE often show change over time in class of lupus nephritis or have mixed forms? How does autoimmunity in SLE evolve? Why does loss of tolerance against nuclear antigens preferentially affect the kidney? Why are immune complex deposits in different glomerular compartments associated with different outcomes? What determines crescent formation in lupus? In this review, we discuss these questions by linking the latest information on lupus pathogenesis into the context of the different classes of lupus nephritis. This should help the basic scientist, the pathologist, and the clinician to gain a more conceptual view on the immunopathology of lupus nephritis.

The pathogenesis of lupus nephritis

Lupus nephritis is an immune complex GN that develops as a frequent complication of SLE. The pathogenesis of lupus nephritis involves a variety of pathogenic mechanisms. The extrarenal etiology of systemic lupus is based on multiple combinations of genetic variants that compromise those mechanisms normally assuring immune tolerance to nuclear autoantigens. This loss of tolerance becomes clinically detectable by the presence of antinuclear antibodies. In addition, nucleic acids released from netting or apoptotic neutrophils activate innate and adaptive immunity via viral nucleic acid-specific Toll-like receptors. Therefore, many clinical manifestations of systemic lupus resemble those of viral infection. In lupus, endogenous nuclear particles trigger IFN-α signaling just like viral particles during viral infection. As such, dendritic cells, T helper cells, B cells, and plasma cells all contribute to the aberrant polyclonal autoimmunity. The intrarenal etiology of lupus nephritis involves antibody binding to multiple intrarenal autoantigens rather than the deposition of circulating immune complexes. Tertiary lymphoid tissue formation and local antibody production add to intrarenal complement activation as renal immunopathology progresses. Here we provide an update on the pathogenic mechanisms that lead to lupus nephritis and provide the rationale for the latest and novel treatment strategies.

The antiviral cytokines IFN-α and IFN-β modulate parietal epithelial cells and promote podocyte loss: implications for IFN toxicity, viral glomerulonephritis, and glomerular regeneration

Interferon (IFN)-α and IFN-β are the central regulators of antiviral immunity but little is known about their roles in viral glomerulonephritis (eg, HIV nephropathy). We hypothesized that IFN-α and IFN-β would trigger local inflammation and podocyte loss. We found that both IFNs consistently activated human and mouse podocytes and parietal epithelial cells to express numerous IFN-stimulated genes. However, only IFN-β significantly induced podocyte death and increased the permeability of podocyte monolayers. In contrast, only IFN-α caused cell-cycle arrest and inhibited the migration of parietal epithelial cells. Both IFNs suppressed renal progenitor differentiation into mature podocytes. In Adriamycin nephropathy, injections with either IFN-α or IFN-β aggravated proteinuria, macrophage influx, and glomerulosclerosis. A detailed analysis showed that only IFN-β induced podocyte mitosis. This did not, however, lead to proliferation, but was associated with podocyte loss via podocyte detachment and/or mitotic podocyte death (mitotic catastrophe). We did not detect TUNEL-positive podocytes. Thus, IFN-α and IFN-β have both common and differential effects on podocytes and parietal epithelial cells, which together promote glomerulosclerosis by enhancing podocyte loss while suppressing podocyte regeneration from local progenitors.

Lupus nephritis. How latest insights into its pathogenesis promote novel therapies

PURPOSE OF REVIEW

Lupus nephritis is a complex autoimmune disease that develops its own dynamic upon damaging the renal ultrastructure. Here, we summarize the latest pathophysiological concepts of lupus nephritis and how these translate into novel therapeutic options.

RECENT FINDINGS

Multidisciplinary research activities form a better understanding about how lupus develops from an unfortunate combination of gene variants that promote the loss of tolerance, that impair the clearance of dying cells, that regulate the immune interpretation of autoantigens as well as the peripheral control of autoreactive lymphocytes. As a new entry, nuclear particles also act as autoadjuvants mimicking viral particles and triggering interferon-alpha-dependent antiviral immune responses that cause symptoms similar to viral infection.

SUMMARY

A set of novel drugs have the potential to more specifically interfere with these pathomechanisms and raise hope to more efficiently treat lupus nephritis with fewer side-effects in the near future.

A novel pathogenetic concept-antiviral immunity in lupus nephritis

Lupus nephritis is a complication of systemic lupus erythematosus, a heterogeneous autoimmune syndrome involving multiple pathways. Accumulating data from the fields of genetics, clinical science, transcriptomics and basic immunology indicate that antiviral immunity has relevance in the pathogenesis of lupus nephritis. This idea is based on the existence of genetic variants that promote the persistence of nuclear particles in the extracellular space or inside lysosomes. Such nuclear particles mimic viral particles and their RNA or DNA components activate viral nucleic acid recognition receptors in antigen-presenting cells. These autoadjuvant effects of endogenous nucleic acids promote an inappropriate immune interpretation of the nuclear particles during antigen presentation. This process fosters the expansion of autoreactive T cells and B cells, which promotes autoantibody production and immune complex glomerulonephritis. The release of interferon α sets off an antiviral immune response with a coordinated induction of hundreds of antiviral genes both inside and outside the kidney. In this article we summarize the available data indicating that innate immunity triggers antiviral immunity in systemic lupus erythematosus. We also discuss the related implications for innovative therapeutic strategies.

Activation of type I interferon pathway in systemic lupus erythematosus: association with distinct clinical phenotypes

Growing evidence over the last few years suggests a central role of type I IFN pathway in the pathogenesis of systemic autoimmune disorders. Data from clinical and genetic studies in patients with systemic lupus erythematosus (SLE) and lupus-prone mouse models, indicates that the type I interferon system may play a pivotal role in the pathogenesis of several lupus and associated clinical features, such as nephritis, neuropsychiatric and cutaneous lupus, premature atherosclerosis as well as lupus-specific autoantibodies particularly against ribonucleoproteins. In the current paper, our aim is to summarize the latest findings supporting the association of type I IFN pathway with specific clinical manifestations in the setting of SLE providing insights on the potential use of type I IFN as a therapeutic target.

Epigenetics in systemic lupus erythematosus: leading the way for specific therapeutic agents

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder of an unclearly determined etiology. Past studies, both epidemiological and biological, have implicated epigenetic influences in disease etiology and pathogenesis. Epigenetics describes changes in gene expression not linked to alterations in the underlying genomic sequence, and is most often typified by three modifications: methylation of DNA, addition of various side chains to histone groups and transcriptional regulation via short ncRNA sequences. The purpose of this article is to review the most important advances that link epigenetic changes to lupus. The contribution of DNA methylation changes to lupus pathogenesis is discussed. These include the role of apoptotic DNA, ultraviolet radiation, endogenous retroviruses, dietary contributions and aging. Hypomethylation of specific genes overexpressed in lupus T cells such as ITGAL (CD11a), CD40LG (CD40L), TNFSF7 (CD70), KIR2DL4 and PRF1 (perforin), and CD5 in lupus B cells seem to play an important role. Moreover, histone modifications such as increased global H4 acetylation in monocytes are highly associated with SLE. NcRNAs, especially miR-21, miR-148a and miR-126, control other elements of epigenetic regulation; particularly, transcription of the maintenance DNA methylation enzyme DNMT1. Epigenetic contributions to SLE etiology have been well established, but much is still unknown. Epigenome-wide studies coupled with functional analysis of the epigenomic changes discovered will uncover novel pathways important in disease pathogenesis. Epigenetic therapies for SLE may be feasible in the future, particularly if they are designed to target specific regions within the genome.

Endogenous retroviral pathogenesis in lupus

PURPOSE OF REVIEW

Genetic and environmental factors influence the development of systemic lupus erythematosus (SLE). Endogenous retroviruses (ERVs) are proposed as a molecular link between the human genome and environmental factors, such as viruses, in lupus pathogenesis.

RECENT FINDINGS

The HRES-1 human ERV encodes a 28-kD nuclear autoantigen and a 24-kD small GTP-ase, termed HRES-1/Rab4. HRES-1/p28 is a target of cross-reactive antiviral antibodies, whereas HRES-1/Rab4 regulates the surface expression of CD4 via endosome recycling. The tat gene of HIV-1 induces the expression of HRES-1/Rab4, which in turn downregulates expression of CD4 and susceptibility to reinfection by HIV-1. HRES-1/Rab4 is overexpressed in lupus T cells where it correlates with increased recycling of CD4 and CD3 and contributes to downregulation of CD3/TCRzeta via lysosomal degradation. Chilblain lupus has been linked to the deficiency of 3'-5' repair exonuclease Trex1 that metabolizes DNA reverse-transcribed from ERV. Trex1 deficiency or blocked integration of ERV-encoded DNA also promotes lupus in murine models.

SUMMARY

ERV proteins may trigger lupus through structural and functional molecular mimicry, whereas the accumulation of ERV-derived nucleic acids stimulates interferon and anti-DNA antibody production in SLE.

Innate immune receptors and autophagy: implications for autoimmune kidney injury

Inflammation is the immune system's response to infectious or noninfectious sources of danger. Danger recognition is facilitated by various innate immune receptor families including the Toll-like receptors (TLRs), which detect danger signals in extracellular and intracellular compartments. It is an evolving concept that renal damage triggers intrarenal inflammation by immune recognition of molecules that are being released by dying cells. Such danger-associated molecules act as immunostimulatory agonists to TLRs and other innate immune receptors and induce cytokine and chemokine secretion, leukocyte recruitment, and tissue remodeling. As a new entry to this concept, autophagy allows stressed cells to reduce intracellular microorganisms, protein aggregates, and cellular organelles by moving and subsequently digesting them in autophagolysosomes. Within the autophagolysosome, endogenous molecules and danger-associated molecules may be presented to TLRs or loaded onto the major histocompatibility complex and presented as autoantigens. Here we discuss the current evidence for the danger signaling concept in autoimmune kidney injury and propose that autophagy-related processing of self-proteins provides a source of immunostimulatory molecules and autoantigens. A better understanding of danger signaling should enable us to unravel yet unknown triggers for renal immunopathology and progressive kidney disease.

Interferon-stimulated gene 15 (ISG15) conjugates proteins in dermatomyositis muscle with perifascicular atrophy

OBJECTIVE

We investigated interferon-stimulated gene 15 (ISG15), a poorly understood ubiquitin-like modifier, and its enzymatic pathway in dermatomyositis (DM), an autoimmune disease primarily involving muscle and skin.

METHODS

We generated microarray data measuring transcript abundance for approximately 18,000 genes in each of 113 human muscle biopsy specimens, and studied biopsy specimens and cultured skeletal muscle using immunohistochemistry, immunoblotting proteomics, real-time quantitative polymerase chain reaction, and laser-capture microdissection.

RESULTS

Transcripts encoding ISG15-conjugation pathway proteins were markedly upregulated in DM with perifascicular atrophy (DM-PFA) muscle (ISG15 339-fold, HERC5 62-fold, and USP18 68-fold) compared with 99 non-DM samples. Combined analysis with publicly available microarray datasets showed that >50-fold ISG15 transcript elevation had 100% sensitivity and specificity for 28 biopsies from adult DM-PFA and juvenile DM patients compared with 199 muscle samples from other muscle diseases. Free ISG15 and ISG15-conjugated proteins were only found on immunoblots from DM-PFA muscle. Cultured human skeletal muscle exposed to type 1 interferons produced similar transcripts and ISG15 protein and conjugates. Laser-capture microdissection followed by proteomic analysis showed deficiency of titin in DM perifascicular atrophic myofibers.

INTERPRETATION

A large-scale microarray study of muscle samples demonstrated that among a diverse group of muscle diseases DM was uniquely associated with upregulation of the ISG15 conjugation pathway. Exposure of human skeletal muscle cell culture to type 1 interferons produced a molecular picture highly similar to that seen in human DM muscle. Perifascicular atrophic myofibers in DM were deficient in a number of skeletal muscle proteins including titin.

Pseudoviral immunity - a novel concept for lupus

Systemic lupus erythematosus (SLE or lupus) is a polygenic syndrome of immunity against nuclear autoantigens. Recent data from several fields now suggest 'pseudoviral' immunity as a novel disease concept. Known lupus risk factors commonly compromise those mechanisms that protect chromatin and ribonucleoprotein particles from activating viral nucleic acid sensors. This process activates antigen-presenting cells and induces type I interferons. These central mediators of antiviral immunity have similar proinflammatory roles in lupus, explaining overlapping clinical manifestations, immunopathology and ultrastructural abnormalities in systemic viral infection and lupus. Structurally, chromatin and ribonucleoprotein particles resemble viral particles and have a similar potency to trigger antigen-specific B- and T-cell responses. Therefore, self nucleic acid-driven 'pseudoviral' immunity is evolving as another concept in understanding the pathogenesis of lupus and may offer novel targets for therapy.

Infection—genetics relationship in systemic lupus erythematosus

Genetic, environmental, and hormonal factors contribute to disease susceptibility in systemic lupus erythematosus. Among environmental factors, infectious agents play a major role. When considering the complex relationship between genetic predisposition and infections in the pathogenesis of systemic lupus erythematosus, we have to consider that infectious agents can interact with the immune system in several ways. For example, molecular mimicry, altered apoptosis of the host cells, exposure of as yet masked antigens to the immune system by a given microorganism, and direct viral invasion of immunocompetent cells are all mechanisms that may give rise to dysfunction of the immune system; in addition, some genetically determined deficit of the immune system, such as complement deficiency or deficit of mannose binding lectine, may cause insufficient clearance of infectious agents, whose persistence in the host may determine autoimmunity. Finally, evidence has been emerging suggesting that the production of autoantibodies, by infected B-lymphocytes, may be drawn by altered expression of particular microRNA in these cells. In this paper, we review some of the distinct scenarios that can account for the role of infectious agents, acting on a genetically prone host, in determining systemic lupus erythematosus.

Cross-talk of the environment with the host genome and the immune system through endogenous retroviruses in systemic lupus erythematosus

Environmental factors are capable of triggering the expression of human endogenous retroviruses and induce an autoimmune response. Infection can promote the expression of human endogenous retroviruses by molecular mimicry or by functional mimicry. There are additional mechanisms which may control the expression of human endogenous retroviruses, such as epigenetic status of the genome (hypomethylation, histone deacetylation). Ultraviolet exposure, chemicals/drugs, injury/stress, hormones, all as a single cause or in a concert, may modulate the involvement of human endogenous retroviruses in pathogenic processes. In the current review we summarize the current knowledge on infections, molecular mimicry, cross-reactivity and epigenetics contribution for trigger human endogenous retroviruses expression and pathogenesis in lupus patients. Lupus (2009) 18, 1136—1143.

Drug-induced Kidney Disease – Pathology and Current Concepts

The kidneys can be damaged by a large number of therapeutic agents. The aim of this article is to discuss the pathological features of drug-induced renal disease as diagnosed by kidney biopsy. The literature is reviewed and cases seen by the authors that have a known drug association are analysed. Mechanisms of injury are varied and all renal structures may be affected. The tubulointerstitial compartment is most frequently involved, but glomerular and vascular lesions are seen in a significant proportion of cases. Key words: Drug, Kidney, Nephrotoxicity, Pathology

Interferon-related transcriptome alterations in the cerebrospinal fluid cells of Aicardi-Goutières patients

Aicardi-Goutières syndrome (AGS) is a rare interferon (IFN)-related encephalopathy with onset during the first year of life. AGS, is clinically characterized by progressive microcephaly, bilateral basal ganglia calcification, cerebral atrophy, cerebrospinal fluid (CSF), lymphocytosis, delayed development of psychomotor abilities with pyramidal-extrapyramidal syndrome and mimics congenital viral infections. Microarray analysis examining the expression of 18 880 human genes has been applied to the CSF lymphocytes of 20 AGS cases (age 4.5 +/- 4.4 years, mean +/- standard deviation) characterized by high IFN-alpha levels in CSF and 20 matched controls (age 4.4 +/- 4.3 years, mean +/- standard deviation). Gene-expression data reveal significant differences between AGS cases and controls for all controls and 18 AGS cases. The two AGS cases unclassified as compared with controls were both older than 7 years. AGS cases presented upregulation of genes involved in IFN-dependent pathways and lymphocyte functions, paralleled by the downregulation of genes encoding for angiopoietic activities. The cystatin F and DNAJ genes, having a negative feedback on IFN pathways, underwent a progressive age-related increase in their expression. These gene-expression signature parallels a progressive attenuation of clinical symptoms with age. Obtained results provide evidence that exposure to IFN-alpha is harmful for developing brain.

Aicardi-Goutières syndrome (AGS)

In 1984, Jean Aicardi and Françoise Goutières described 8 children showing both severe brain atrophy and chronic cerebrospinal fluid lymphocytosis, with basal ganglia calcification in at least one member of each affected family. The course was rapid to death or a vegetative outcome. Aicardi and Goutières correctly predicted that the disorder would be genetic, but emphasised that "some features, especially the pleocytosis, may erroneously suggest an inflammatory condition". The increased interferon-alpha in affected children (Pierre Lebon, Paris) mimicked congenital viral infection, but the associated chilblains (pernio) pointed to lupus erythematosus and an autoimmune mechanism. Genetic research led by Yanick Crow has clarified these puzzling relationships in Aicardi-Goutières syndrome, a syndrome that now includes conditions previously known as microcephaly-intracranial calcification syndrome, pseudo-TORCH and Cree encephalitis. At the time of writing, Crow's team has discovered that over 80% of families with Aicardi-Goutières syndrome have mutations in one of four nuclease genes, the exonuclease TREX1 and the genes for all three subunits of the ribonuclease H2 enzyme complex. Aicardi-Goutières syndrome is both genetically and phenotypically heterogeneous, with a range of severity from life-threatening perinatal illness to mild late infancy onset. All infants of whatever genotype have increased interferon-alpha in the first year of life and this appears to be the final common pathway that links Aicardi-Goutières syndrome, congenital virus infection and systemic lupus erythematosus.

Molecular mimicry and immunomodulation by the HRES-1 endogenous retrovirus in SLE

Genetic and environmental factors are believed to influence development of systemic lupus erythematosus (SLE). Endogenous retroviruses (ERV) correspond to the integrated proviral form of infectious retroviruses, which are trapped within the genome due to mutations. ERV represent a key molecular link between the host genome and infectious viral particles. ERV-encoded proteins are recognized by antiviral immune responses and become targets of autoreactivity. Alternatively, ERV protein may influence cellular processes and the life cycle of infectious viruses. As examples, the HRES-1 human ERV encodes a 28-kDa nuclear autoantigen and a 24-kDa small GTP-ase, termed HRES-1/Rab4. HRES-1/p28 is a nuclear autoantigen recognized by cross-reactive antiviral antibodies, while HRES-1/Rab4 regulates surface expression of CD4 and the transferrin receptor (TFR) through endosome recycling. Expression of HRES-1/Rab4 is induced by the tat gene of HIV-1, which in turn down-regulates expression of CD4 and susceptibility to re-infection by HIV-1. CD4 and the TFR play essential roles in formation of the immunological synapse (IS) during normal T-cell activation by a cognate MHC class II peptide complex. The key intracellular transducer of T-cell activation, Lck, is brought to the IS via binding to CD4. T-cell receptorzeta (TCRzeta) chain binds to the TFR. Abnormal T-cell responses in SLE have been associated with reduced lck and TCRzeta chain levels. HRES-1 is centrally located on chromosome 1 at q42 relative to lupus-linked microsatellite markers and polymorphic HRES-1 alleles have been linked to the development of SLE. 1q42 is one of the three most common fragile sites in the human genome, and is inducible by DNA demethylation, a known mechanism of retroviral gene activation. Molecular mimicry and immunomodulation by a ERV, such as HRES-1, may contribute to self-reactivity and abnormal T and B-cell functions in SLE.

Interferons: cytokines in autoimmunity

The presence of circulating interferons in the blood of patients with autoimmune diseases and the acquired immune deficiency syndrome (AIDS) raises the question of their possible pathogenetic or defence functions. Interferons control levels of HLA class I and II antigens on cells and can activate or inhibit immune killer cell activities. Tumour necrosis factors (TNF) and interleukin 1 induce a new autocrine species of interferon known as IFN-beta-2 whose gene has been cloned, sequenced and expressed. This IFN mediates the increase in HLA expression caused by TNF as well as the antiviral activity of this cytotoxin.

Ultrastructural observations in a case of BK virus nephropathy with viruses in glomerular subepithelial humps

BK virus nephropathy is a known cause of renal transplant dysfunction and failure. The disease is identified by examination of kidney biopsy tissue utilizing histopathological techniques. Ultrastructural examination of two glomeruli revealed pathology within one glomerulus. Glomerular basement membranes contained subepithelial humps of deposit-like material and BK viruses were identified within this material. Viruses were identified within intertubular capillaries. There was evidence of cytoplasmic clearance of viruses from the glomerular basement membrane by podocytes. The findings may be relevant to the investigation of hump formation and antigen clearance in BK virus nephropathy and postinfectious glomerulonephritis.

Interferon pathway activation in systemic lupus erythematosus

The recognition that a multitude of interferon (IFN)- inducible genes are coordinately expressed in peripheral blood cells of patients with systemic lupus erythematosus (SLE) has contributed to considerable interest in the IFN pathway as a therapeutic target in lupus. Together with data that have accumulated over the past four decades implicating IFN-alpha in SLE, the gene expression data have resulted in emergence of this cytokine pathway as a focal point for understanding mechanisms of autoimmunity and inflammation in systemic autoimmune diseases. Assays that measure IFN-inducible gene expression in patient cells and tissues and plasma assays that quantify IFN-alpha protein are providing tools for identification of patients with active disease and who may be responsive to inhibition of the innate immune system component of the altered immune response in SLE. In addition, investigations of the mechanisms of induction of IFN pathway activation are suggesting clues to the triggers of autoimmunity in SLE.

Lupus Nephritis

Lupus nephritis is one of the more serious manifestations of the systemic autoimmune disease, systemic lupus erythematosus, and is associated with considerable morbidity and even mortality. Treatment remains problematic, particularly in terms of controlling the underlying disease process while at the same time preventing unacceptable side effects of therapy. In recent years, clinical trials have started to define optimum regimens of the immunosuppressive agents presently in use. The etiology and pathogenesis of systemic lupus erythematosus and lupus nephritis still are understood incompletely. Nevertheless, insights gained from basic science research in both animals and human beings now are being translated into newer therapies that have the potential to be safer and more specific than those currently available.

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.

Interferon-α/β-mediated innate immune mechanisms in dermatomyositis

Dermatomyositis has been modeled as an autoimmune disease largely mediated by the adaptive immune system, including a local humorally mediated response with B and T helper cell muscle infiltration, antibody and complement-mediated injury of capillaries, and perifascicular atrophy of muscle fibers caused by ischemia. To further understand the pathophysiology of dermatomyositis, we used microarrays, computational methods, immunohistochemistry and electron microscopy to study muscle specimens from 67 patients, 54 with inflammatory myopathies, 14 with dermatomyositis. In dermatomyositis, genes induced by interferon-alpha/beta were highly overexpressed, and immunohistochemistry for the interferon-alpha/beta inducible protein MxA showed dense staining of perifascicular, and, sometimes all myofibers in 8/14 patients and on capillaries in 13/14 patients. Of 36 patients with other inflammatory myopathies, 1 patient had faint MxA staining of myofibers and 3 of capillaries. Plasmacytoid dendritic cells, potent CD4+ cellular sources of interferon-alpha, are present in substantial numbers in dermatomyositis and may account for most of the cells previously identified as T helper cells. In addition to an adaptive immune response, an innate immune response characterized by plasmacytoid dendritic cell infiltration and interferon-alpha/beta inducible gene and protein expression may be an important part of the pathogenesis of dermatomyositis, as it appears to be in systemic lupus erythematosus.

Aicardi-Goutières syndrome

Aicardi-Goutieres syndrome is a familial progressive early onset encephalopathy with basal ganglia calcifications, chronic CSF lymphocytosis and high level of interferon-alpha in CSF. Cutaneous necrotic lesions and the neuropathological aspect of microangiopathy and microinfarctions suggest a vascular process in relation to elevated interferon-alpha. A genetic defect in the regulation of its synthesis may be the causal factor of the disorder.

Microarray analysis of interferon-regulated genes in SLE

Altered regulation of interferon-alpha (IFNalpha) in systemic lupus erythematosus (SLE) was first demonstrated nearly 25 years ago. However, only recently has due attention been directed towards the central role of this cytokine family in SLE. Several laboratories have used large-scale microarray technology to study global gene expression patterns in heterogeneous populations of peripheral blood cells from lupus patients and control subjects. The results of these studies demonstrate that IFN-regulated genes are among the most significantly overexpressed in SLE mononuclear cells. In view of the protean effects of IFNs on immune system function, increased activity of IFNs may account for many of the immune system alterations that characterize SLE and contribute to autoimmunity. Definition of the nature of the major IFNs, or other factors, that drive the IFN-regulated gene expression signature noted in SLE is an important area for investigation that may lead to new approaches to targeted therapy of SLE.

Uncertainties in the pathogenesis of adult dermatomyositis

PURPOSE OF REVIEW

Dermatomyositis is an inflammatory disorder of muscle affecting both children and adults. The pathogenesis of adult dermatomyositis is reviewed here, with particular attention to gaps and uncertainties in our current understanding of this disease, in order to focus attention on the outstanding research questions with regard to disease mechanisms.

RECENT FINDINGS

The conceptual model of the pathophysiology of dermatomyositis has been based on work extending back over at least 35 years, with important findings related to the deposition of membrane attack complex, the character of the inflammatory infiltrate, and the primacy of capillary abnormalities established over 10 years ago. The lack of significant additions to the understanding of this disease over the past few years suggests a state of contentment with current knowledge. Accordingly, we emphasize the uncertainties of this knowledge and the need for re-addressing some of its basic tenets.

SUMMARY

Although evidence remains strong that dermatomyositis is a disorder with an early involvement of the capillaries, the concept that it results from an antibody-mediated attack upon the endothelium is uncertain. It is not clear whether membrane attack complex is activated by antibody-dependent or independent means, whether or not intramuscular B cells are antigen specific and synthesize significant quantities of antibodies, whether the presence of tubuloreticular inclusions precedes, follows, or is independent of membrane attack complex deposition, what is the mechanism of perifascicular atrophy, and what is the relationship of dermatomyositis to systemic lupus erythematosus.

BK polyoma virus allograft nephropathy: ultrastructural features from viral cell entry to lysis

BK virions must enter the host cell and target their genome to the nucleus in order to complete their life cycle. The mechanisms by which the virions accomplish these tasks are not known. In this morphological study we found that BK virions localized beneath the host cell cytoplasmic membrane in 60-70-nm, smooth (non-coated) monopinocytotic vesicles similar to, or consistent with, caveolae. In the cytoplasm, the monopinocytotic vesicles carrying virions appeared to fuse with a system of smooth, vesicles and tubules that communicated with the rough endoplasmic reticulum and was continuous with the Golgi system. Membrane-bound single virions and large tubulo-reticular complexes loaded with virions accumulated in paranuclear locations. Occasional nuclei displayed virions within the perinuclear cisterna in association to the perinuclear viral accumulations. Tubular cells with mature productive infection had large nuclei, distended by daughter virions, whereas they lacked significant numbers of cytoplasmic virions. In addition to virally induced cell necrosis, there was extensive tubular cell damage (apoptosis and necrosis) in morphologically non-infected tubules. The observed ultrastructural interactions between the BK virions and host cells are remarkably similar to viral cell entry and nuclear targeting described for SV40 virus.

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.

Role of endogenous retroviruses in autoimmune diseases

Endogenous retroviruses (ERVs) correspond to the integrated proviral form of infectious retroviruses that are trapped within the genome by mutations. Endogenous retroviruses represent a key molecular link between the host genome and infectious viral particles. Proteins encoded by ERVs are recognized by antiviral immune responses and become targets of autoreactivity. Activation of ERVs, such as human ERV-K or a human T-cell lymphotropic virus-related endogenous sequence, may also mediate pathogenicity of Epstein-Barr virus. Endogenous retrovirus peptides can directly regulate immune responses. Thus, molecular mimicry and immunomodulation by ERVs may account for self-reactivity and abnormal T- and B-cell functions in autoimmune disorders.

The value of electron microscopy in the diagnosis and clinical management of lupus nephritis

The diagnosis and clinical management of patients with lupus nephritis can be a challenge from a clinicopathologic point of view. Although the majority of patients that are biopsied already have either an established clinical diagnosis or a presumptive diagnosis of systemic lupus erythematosus, determination of the immunomorphologic characteristics, pattern, and distribution of renal involvement is important for clinical management. In a clear subset of these patients with lupus nephritis, electron microscopy plays a pivotal role in accurately characterizing the type of renal involvement and determining the degree of activity, providing useful and objective guides for patients' management. Ultrastructural evaluation can also be crucial in the initial diagnosis of patients with lupus who, at the time of biopsy, lack either diagnostic clinical manifestations and/or serologic markers, and are therefore clinically unsuspected. Electron microscopic evaluation also plays a significant role in the evaluation of renal dysfunction in transplant patients with lupus nephritis, helping to determine whether recurrence of the lupus has occurred in the renal allograft. There are some ultrastructural findings that, although not pathognomonic, in the proper clinico-pathologic context are very suggestive or even diagnostic of lupus nephritis. Correlating light, immunofluorescence, and electron microscopic findings within the clinical context of lupus nephritis cases is crucial for appropriate clinical management. In some of these patients, electron microscopy provides key information that cannot be otherwise obtained.