Reduced perforin expression in systemic juvenile idiopathic arthritis is restored by autologous stem-cell transplantation

Immunology of Cytokine Storm Syndromes: Natural Killer Cells

Natural killer (NK) cells are innate immune lymphocytes that rapidly produce cytokines upon activation and kill target cells. NK cells have been of particular interest in primary hemophagocytic lymphohistiocytosis (pHLH) since all of the genetic defects associated with this disorder cause diminished cytotoxic capacity of NK cells and T lymphocytes, and assays of NK cell killing are used clinically for the diagnosis of HLH. Herein, we review human NK cell biology and the significance of alterations in NK cell function in the diagnosis and pathogenesis of HLH.

Molecular Pathways in the Pathogenesis of Systemic Juvenile Idiopathic Arthritis

Systemic juvenile idiopathic arthritis (sJIA) is a rare childhood chronic inflammatory disorder with risk for life-threatening complications including macrophage activation syndrome and lung disease. At onset, sJIA pathogenesis resembles that of the autoinflammatory periodic fever syndromes with marked innate immune activation, expansion of neutrophils and monocytes, and high levels of interleukin-18. Here, we review the current conceptual understanding of sJIA pathogenesis with a focus on both innate and adaptive immune pathways. Finally, we consider how recent progress toward understanding the immunologic basis of sJIA may support new therapies for refractory disease courses.

Immune-mediated inflammatory diseases with chronic excess of serum interleukin-18

Review: Interleukin-18 (IL-18) is a proinflammatory cytokine that promotes various innate immune processes related to infection, inflammation, and autoimmunity. Patients with systemic juvenile idiopathic arthritis and adult-onset Still’s disease exhibit chronic excess of serum IL-18, which is associated with a high incidence of macrophage activation syndrome (MAS), although the mechanisms of IL-18 regulation in such diseases remain largely unknown. Similar elevation of serum IL-18 and susceptibility to MAS/hemophagocytic lymphohistiocytosis (HLH) have been reported in monogenic diseases such as X-linked inhibitor of apoptosis deficiency (i.e., X-linked lymphoproliferative syndrome type 2) and NLRC4-associated autoinflammatory disease. Recent advances in molecular and cellular biology allow the identification of other genetic defects such as defects in CDC42, PSTPIP1, and WDR1 that result in high serum IL-18 levels and hyperinflammation. Among these diseases, chronic excess of serum IL-18 appears to be linked with severe hyperinflammation and/or predisposition to MAS/HLH. In this review, we focus on recent findings in inflammatory diseases associated with and probably attributable to chronic excess of serum IL-18 and describe the clinical and therapeutical relevance of understanding the pathology of this group of diseases.

Haematopoietic stem cell transplantation in paediatric rheumatic disease

PURPOSE OF REVIEW

A small proportion of children affected by rheumatic diseases suffer from severe, progressive disease, resistant to conventional antirheumatic therapies and to biologic agents interfering with inflammatory cytokines, costimulatory molecules expressed on immune system cells and intracellular signalling pathways. Adding to the poor prognosis is a high risk from significant morbidity and mortality associated with long-term treatment with multiple, often combined anti-inflammatory and immunosuppressive agents. Carefully selected patients from this unfortunate group may benefit from treatment with haematopoietic stem cell transplantation.

RECENT FINDINGS

The majority of patients with severe paediatric rheumatic and autoinflammatory diseases treated with autologous and/or allogeneic haematopoietic stem cell transplantation achieved long-term remission. However, the incidence of disease relapse and transplant related morbidity and mortality is still significant.

SUMMARY

Careful patient and donor selection, timing of the transplant earlier in the course of disease rather than the 'last resort' and choosing the most suitable conditioning regimen for each individual patient are the major factors favouring successful outcome. Close co-operation between the patients, their family, and involved medical teams is essential.

Macrophage activation syndrome in systemic juvenile idiopathic arthritis

Macrophage activation syndrome (MAS) is a severe, potentially life-threatening complication of systemic juvenile idiopathic arthritis (s-JIA). An immunological feature is the excessive activation and proliferation of T lymphocytes and macrophages. Massive hypercytokinemia is strongly associated with its pathogenesis, particularly the overproduction of interleukin (IL)-1, IL-6 and IL-18; interferon (IFN)-γ; and tumor necrosis factor (TNF)-α. Furthermore, heterozygous mutations in causative genes for primary hemophagocytic lymphohistiocytosis and in vivo exposure to highly elevated levels of IL-6 and IL-18 might induce natural killer cell dysfunction and decrease their numbers, respectively. A proper diagnosis is important to begin appropriate therapeutic interventions and change an unfavorable prognosis. The 2016 ACR/EULAR classification criteria for MAS have a high diagnostic performance; however, the diagnostic sensitivity for onset is relatively low. Therefore, careful monitoring of laboratory values during the course of MAS is necessary to diagnose it early in s-JIA. Further studies on the diagnosis and monitoring of disease activity using serum cytokine profile and a targeted cytokine strategy are required.

Adult-Onset Still's Disease: Clinical Aspects and Therapeutic Approach

Adult-onset Still's disease (AoSD) is a rare systemic autoinflammatory disease characterized by arthritis, spiking fever, skin rash and elevated ferritin levels. The reason behind the nomenclature of this condition is that AoSD shares certain symptoms with Still's disease in children, currently named systemic-onset juvenile idiopathic arthritis. Immune dysregulation plays a central role in AoSD and is characterized by pathogenic involvement of both arms of the immune system. Furthermore, the past two decades have seen a large body of immunological research on cytokines, which has attributed to both a better understanding of AoSD and revolutionary advances in treatment. Additionally, recent studies have introduced a new approach by grouping patients with AoSD into only two phenotypes: one with predominantly systemic features and one with a chronic articular disease course. Diagnosis presupposes an extensive diagnostic workup to rule out infections and malignancies. The severe end of the spectrum of this disease is secondary haemophagocytic lymphohistiocytosis, better known as macrophage activation syndrome. In this review, we discuss current research conducted on the pathogenesis, diagnosis, classification, biomarkers and complications of AoSD, as well as the treatment strategy at each stage of the disease course. We also highlight the similarities and differences between AoSD and systemic-onset juvenile idiopathic arthritis. There is a considerable need for large multicentric prospective trials.

Immunopathogenesis and treatment of cytokine storm in COVID-19

Severe coronavirus disease 2019 (COVID-19) is characterized by systemic hyper-inflammation, acute respiratory distress syndrome, and multiple organ failure. Cytokine storm refers to a set of clinical conditions caused by excessive immune reactions and has been recognized as a leading cause of severe COVID-19. While comparisons have been made between COVID-19 cytokine storm and other kinds of cytokine storm such as hemophagocytic lymphohistiocytosis and cytokine release syndrome, the pathogenesis of cytokine storm has not been clearly elucidated yet. Recent studies have shown that impaired response of type-1 IFNs in early stage of COVID-19 infection played a major role in the development of cytokine storm, and various cytokines such as IL-6 and IL-1 were involved in severe COVID-19. Furthermore, many clinical evidences have indicated the importance of anti-inflammatory therapy in severe COVID-19. Several approaches are currently being used to treat the observed cytokine storm associated with COVID-19, and expectations are especially high for new cytokine-targeted therapies, such as tocilizumab, anakinra, and baricitinib. Although a number of studies have been conducted on anti-inflammatory treatments for severe COVID-19, no specific recommendations have been made on which drugs should be used for which patients and when. In this review, we provide an overview of cytokine storm in COVID-19 and treatments currently being used to address it. In addition, we discuss the potential therapeutic role of extracorporeal cytokine removal to treat the cytokine storm associated with COVID-19.

Hemophagocytic lymphohistiocytosis: a review inspired by the COVID-19 pandemic

Hemophagocytic syndrome (HPS) or hemophagocytic lymphohistiocytosis (HLH) is an acute and rapidly progressive systemic inflammatory disorder characterized by cytopenia, excessive cytokine production, and hyperferritinemia. Common clinical manifestations of HLH are acute unremitting fever, lymphadenopathy, hepatosplenomegaly, and multiorgan failure. Due to a massive cytokine release, this clinical condition is considered as a cytokine storm syndrome. HPS has primary and acquired (secondary, reactive) forms. Its primary form is mostly seen in childhood and caused by various mutations with genetic inheritance and, therefore, is called familial HLH. Secondary HLH may be caused in the presence of an underlying disorder, that is, secondary to a malignant, infectious, or autoimmune/autoinflammatory stimulus. This paper aims to review the pathogenesis and the clinical picture of HLH, and its severe complication, the cytokine storm, with a special emphasis on the developed classification criteria sets for rheumatologists, since COVID-19 infection has clinical symptoms resembling those of the common rheumatologic conditions and possibly triggers HLH. MED-LINE/Pubmed was searched from inception to April 2020, and the following terms were used for data searching: “hemophagocytic syndrome” OR “macrophage activation syndrome” OR “hemophagocytic lymphohistiocytosis”, OR “cytokine storm”. Finally, AND “COVID-19” was included in this algorithm. The selection is restricted to the past 5 years and limited numbers of earlier key references were manually selected. Only full-text manuscripts, published in an English language peer-reviewed journal were included. Manuscript selection procedure and numbers are given in Fig. 2. Briefly, the database search with the following terms of “Hemophagocytic syndrome” OR “Macrophage activation syndrome” OR “Hemophagocytic lymphohistiocytosis” OR “Cytokine storm” yielded 6744 results from inception to April 2020. The selection is restricted to the past 5 years and only limited numbers of earlier key references were selected, and this algorithm resulted in 3080 manuscripts. The addition of (AND “COVID-19”) resulted in 115 publications of which 47 studies, together with four sections of an online book were used in the final review. No statistical method was used. HLH is triggered by genetic conditions, infections, malignancies, autoimmune-autoinflammatory diseases, and some drugs. In COVID-19 patients, secondary HLH and cytokine storm may be responsible for unexplained progressive fever, cytopenia, ARDS, neurological and renal impairment. Differentiation between the primary and secondary forms of HLH is utterly important, since primary form of HLH requires complicated treatments such as hematopoietic stem cell transplantation. Further studies addressing the performance of HScore and other recommendations in the classification of these patients is necessary.

Significance of KIR like natural killer cell receptors in autoimmune disorders

Killer cell immunoglobulin-like receptors (KIRs), act as the regulators for the cytolytic activity of natural killer and certain T cells by interacting with the HLA class I ligands. KIRs have been shown to contribute to the pathogenesis of several autoimmune diseases. However, their specific roles are still not very clear. Autoimmune diseases are multifactorial in nature, highlighting the influence of both genetic and environmental factors. The innate immune response plays an important role in autoimmunity as it alters the self-glycans that mimic molecular patterns found on different intracellular pathogens. Natural killer (NK) cells have an important position in the innate immune response. NK cell receptors are encoded by the leukocyte receptor complex located on the chromosome 19q13.4 and lectin-like receptors on chromosome 12p13. This review focuses on the role of KIRs and their relationship with different autoimmune diseases.

Natural Killer Cells in Systemic Autoinflammatory Diseases: A Focus on Systemic Juvenile Idiopathic Arthritis and Macrophage Activation Syndrome

Natural killer (NK) cells are innate immune lymphocytes with potent cytolytic and immune-regulatory activities. NK cells are well-known for their ability to kill infected and malignant cells in a fast and non-specific way without prior sensitization. For this purpose, NK cells are equipped with a set of cytotoxic molecules such as perforin and apoptosis-inducing proteins. NK cells also have the capacity to produce large amounts of cytokines and chemokines that synergize with their cytotoxic function and that ensure interaction with other immune cells. A less known feature of NK cells is their capacity to kill non-infected autologous cells, such as immature dendritic cells and activated T cells and monocytes. Via the release of large amounts of TNF-α and IFN-γ, NK cells may contribute to disease pathology. Conversely they may exert a regulatory role through secretion of immuno-regulatory cytokines such as GM-CSF, IL-13, and IL-10. Thus, NK cells may be important target and effector cells in the pathogenesis of autoinflammatory diseases, in particular in those disorders associated with a cytokine storm or in conditions where immune cells are highly activated. Key examples of such diseases are systemic juvenile idiopathic arthritis (sJIA) and its well-associated complication, macrophage activation syndrome (MAS). sJIA is a chronic childhood immune disorder of unknown etiology, characterized by arthritis and systemic inflammation, including a daily spiking fever and evanescent rash. MAS is a potentially fatal complication of autoimmune and autoinflammatory diseases, and most prevalently associated with sJIA. MAS is considered as a subtype of hemophagocytic lymphohistiocytosis (HLH), a systemic hyperinflammatory disorder characterized by defective cytotoxic pathways of cytotoxic T and NK cells. In this review, we describe the established features of NK cells and provide the results of a literature survey on the reported NK cell abnormalities in monogenic and multifactorial autoinflammatory disorders. Finally, we discuss the role of NK cells in the pathogenesis of sJIA and MAS.

Regulatory Role for NK Cells in a Mouse Model of Systemic Juvenile Idiopathic Arthritis

Mice deficient in IFN-γ (IFN-γ knockout [KO] mice) develop a systemic inflammatory syndrome in response to CFA, in contrast to CFA-challenged wild-type (WT) mice who only develop a mild inflammation. Symptoms in CFA-challenged IFN-γ KO resemble systemic juvenile idiopathic arthritis (sJIA), a childhood immune disorder of unknown cause. Dysregulation of innate immune cells is considered to be important in the disease pathogenesis. In this study, we used this murine model to investigate the role of NK cells in the pathogenesis of sJIA. NK cells of CFA-challenged IFN-γ KO mice displayed an aberrant balance of activating and inhibitory NK cell receptors, lower expression of cytotoxic proteins, and a defective NK cell cytotoxicity. Depletion of NK cells (via anti-IL-2Rβ and anti-Asialo-GM1 Abs) or blockade of the NK cell activating receptor NKG2D in CFA-challenged WT mice resulted in increased severity of systemic inflammation and appearance of sJIA-like symptoms. NK cells of CFA-challenged IFN-γ KO mice and from anti-NKG2D-treated mice showed defective degranulation capacities toward autologous activated immune cells, predominantly monocytes. This is in line with the increased numbers of activated inflammatory monocytes in these mice which was particularly reflected in the expression of CCR2, a chemokine receptor, and in the expression of Rae-1, a ligand for NKG2D. In conclusion, NK cells are defective in a mouse model of sJIA and impede disease development in CFA-challenged WT mice. Our findings point toward a regulatory role for NK cells in CFA-induced systemic inflammation via a NKG2D-dependent control of activated immune cells.

Macrophage activation syndrome in adults: recent advances in pathophysiology, diagnosis and treatment

Haemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory syndrome, which if not promptly treated, can lead rapidly to critical illness and death. HLH is termed macrophage activation syndrome (MAS) when associated with rheumatic disease (where it is best characterized in systemic JIA) and secondary HLH (sHLH) when associated with other triggers including malignancy and infection. MAS/sHLH is rare and coupled with its mimicry of other conditions, is underrecognized. These inherent challenges can lead to diagnostic and management challenges in multiple medical specialties including haematology, infectious diseases, critical care and rheumatology. In this review we highlight the pathogenesis of MAS/sHLH including its underlying triggers, key clinical features and diagnostic challenges, prognostic factors and current treatments in adults.

Neutralization of IFN-γ reverts clinical and laboratory features in a mouse model of macrophage activation syndrome

BACKGROUND

The pathogenesis of macrophage activation syndrome (MAS) is not clearly understood: a large body of evidence supports the involvement of mechanisms similar to those implicated in the setting of primary hemophagocytic lymphohistiocytosis.

OBJECTIVE

We sought to investigate the pathogenic role of IFN-γ and the therapeutic efficacy of IFN-γ neutralization in an animal model of MAS.

METHODS

We used an MAS model established in mice transgenic for human IL-6 (IL-6TG mice) challenged with LPS (MAS mice). Levels of IFN-γ and IFN-γ-inducible chemokines were evaluated by using real-time PCR in the liver and spleen and by means of ELISA in plasma. IFN-γ neutralization was achieved by using the anti-IFN-γ antibody XMG1.2 in vivo.

RESULTS

Mice with MAS showed a significant upregulation of the IFN-γ pathway, as demonstrated by increased mRNA levels of Ifng and higher levels of phospho-signal transducer and activator of transcription 1 in the liver and spleen and increased expression of the IFN-γ-inducible chemokines Cxcl9 and Cxcl10 in the liver and spleen, as well as in plasma. A marked increase in Il12a and Il12b expression was also found in livers and spleens of mice with MAS. In addition, mice with MAS had a significant increase in numbers of liver CD68⁺ macrophages. Mice with MAS treated with an anti-IFN-γ antibody showed a significant improvement in survival and body weight recovery associated with a significant amelioration of ferritin, fibrinogen, and alanine aminotransferase levels. In mice with MAS, treatment with the anti-IFN-γ antibody significantly decreased circulating levels of CXCL9, CXCL10, and downstream proinflammatory cytokines. The decrease in CXCL9 and CXCL10 levels paralleled the decrease in serum levels of proinflammatory cytokines and ferritin.

CONCLUSION

These results provide evidence for a pathogenic role of IFN-γ in the setting of MAS.

Adult-onset Still's disease: Advances in the treatment

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder mainly characterized by persistent high spiking fevers, evanescent rash, and joint involvement. The pathogenesis of AOSD is only partially known, but pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1, IL-6, IL-18, and IFN-γ seem to play a major role in this disorder. AOSD is at the crossroad of auto-inflammatory syndromes and autoimmune diseases. It is diagnosed by exclusion to determine the presence of high serum ferritin levels, which is usually >1000 μg/L. AOSD is generally treated with non-steroidal anti-inflammatory drugs, corticosteroids, and disease-modifying anti-rheumatic drugs (DMARDs). Although information on biologic therapy in the management of AOSD is scarce, these drugs represent a major breakthrough in the management of patients with AOSD refractory to corticosteroids or conventional DMARDs or in patients presenting life-threatening manifestations. In this regard, TNF-α, IL-1, and IL-6 antagonists had been proved effective in patients with AOSD.

Intravascular large B-cell lymphoma associated with silicone breast implant, HLA-DRB1*11:01, and HLA-DQB1*03:01 manifesting as macrophage activation syndrome and with severe neurological symptoms: a case report

BACKGROUND

Silicone implants have been successfully used for breast augmentation and reconstruction in millions of women worldwide. The reaction to the silicone implant is highly variable; it can lead to local inflammatory symptoms, and sometimes to systemic symptoms and disease. Over 80 cases of anaplastic lymphoma kinase-negative anaplastic large cell lymphoma have been reported in patients with silicone breast implants and have been accepted as a new clinical entity. To the best of our knowledge, an intravascular large B-cell lymphoma associated with a silicone breast implant has not been reported previously.

CASE PRESENTATION

A 48-year-old Caucasian woman who presented with high fever was found to have splenomegaly on physical examination. A laboratory diagnosis revealed pancytopenia, hypertriglyceridemia, and hyperferritinemia. She developed signs of altered sensorium, hemiparesis, aphasia, and cauda equina syndrome. On further evaluation, she fulfilled the necessary five out of eight criteria for diagnosis of macrophage activation syndrome/hemophagocytic lymphohistiocytosis. Dexamethasone administration was followed by prompt improvement; however, 3 days later she again manifested high fever, which persisted despite administration of immunoglobulin and cyclosporine A. Her silicone breast implant was considered a possible contributor to her macrophage activation syndrome and was therefore removed. A histological examination of the capsule tissue showed an extensive lymphohistiocytic/giant cell foreign body reaction suggestive of autoimmune/inflammatory syndrome induced by adjuvants. However, the histological examination unexpectedly also revealed an intravascular large B-cell lymphoma.

CONCLUSIONS

The genetic background of our patient with silicone breast implants might have predisposed her to three rare and difficult to diagnose syndromes/diseases: macrophage activation syndrome/hemophagocytic lymphohistiocytosis, autoimmune/inflammatory syndrome induced by adjuvants, and intravascular large B-cell lymphoma. The simultaneous manifestation of all three syndromes suggests causal interrelationships. Human leukocyte antigen testing in all women who undergo silicon breast implantation could in the future enable us to better evaluate the risk of potential side effects.

Understanding the spectrum of haemophagocytic lymphohistiocytosis: update on diagnostic challenges and therapeutic options

The cytokine storm syndrome 'haemophagocytic lymphohistiocytosis' (HLH) is an under-recognized hyperinflammatory disorder, causing high morbidity and mortality risk in children and adults. It can be subdivided into a primary, genetic form and a secondary, acquired form that complicates diverse infections, malignancies and autoimmune or autoinflammatory disorders. Both subtypes present with the same spectrum of non-specific symptoms, making accurate diagnosis and rapid treatment initiation challenging. In the last decade, increased awareness and international collaborative efforts fuelled a marked progress in diagnostic protocols and novel treatment strategies for HLH and new diagnostic guidelines are being tailored to specific secondary HLH subtypes. Therapy is gradually shifting its focus from overall immunosuppression towards targeting specific cytokines, cell types or signalling pathways underlying pathophysiology. Nevertheless, continued research efforts remain indispensable to customize therapy to individual patient needs.

The role of natural killer cells in pathogenesis of autoimmune diseases

There is growing evidence that NK cell-mediated immunoregulation plays an important role in the control of autoimmunity. NK cells are a subset of lymphocytes that generally contribute to innate immunity but have also a great impact on the function of T and B lymphocytes. The major role of NK cells is cytotoxic reaction against neoplastic, infected and autoreactive cells, but they regulatory function seems to play more important role in the pathogenesis of autoimmune diseases. Numerous studies suggested the involvement of NK cells in pathogenesis of such a common autoimmune diseases as juvenile rheumatoid arthritis, type I diabetes and autoimmune thyroid diseases. The defects of NK cells regulatory function as well as cytotoxic abilities are common in patients with autoimmune diseases with serious consequences including HLH hemophagocytic lymphocytosis (HLH) and macrophage activation syndrome (MAS). The early diagnosis of NK cells defect responsible for the loss of the protective abilities is crucial for the prevention of life-threatening complications and implementation of necessary treatment.

Screening assays for primary haemophagocytic lymphohistiocytosis in children presenting with suspected macrophage activation syndrome

BACKGROUND

Primary haemophagocytic lymphohistiocytosis (HLH) screening assays are increasingly being performed in patients presenting with macrophage activation syndrome (MAS). The objective of this study was to describe their diagnostic and prognostic relevance in children who had presented to paediatric rheumatology and had undergone investigative work up for MAS.

METHODS

Data was obtained retrospectively from an existing protein screening assay database and patient records. Assays included: intracellular expression of perforin in CD56+ Natural Killer (NK) cells; CD107a Granule Release Assay (GRA) in response to PHA in NK cells, or anti-CD3 stimulation of CD8 lymphocytes; in males Signal Lymphocyte Activating Molecule Associated Protein (SAP), and X-linked Inhibitor of Apoptosis Protein (XIAP) expression. All assays, requested by paediatric rheumatology, of children who had undergone investigative work up for MAS over a 5-year period (2007-2011) were included.

RESULTS

Twenty-one patients (15 female), median age 6.5 years (range 0.6-16) with follow-up of 16 months (range 1-51), were retrospectively identified. At presentation, 3/21 (14 %) fulfilled HLH-2004 diagnostic criteria. At least one screening test result was available for all 21 patients; 7/21 (33 %) had at least one persistent screening test abnormality. Of this group 4/7 (57 %) died or required haematopoietic stem cell transplantation (HSCT), compared to 1/14 (7 %) with no screening test abnormality (p = 0.025). 3/21 (14 %) ultimately had a diagnosis of primary HLH (two confirmed genetically; XIAP, familial HLH type 3, and one confirmed clinically). Of the six patients with abnormal GRA 5/6 had negative routine genetic results.

CONCLUSIONS

Screening for primary HLH is warranted for children whose first rheumatological presentation is with MAS, since overall 14 % had an eventual diagnosis of primary HLH. A persistently abnormal GRA in patients presenting with MAS defines a high-risk group with poor outcome (mortality or HSCT), possibly due to as yet unidentified genetic cause.

Complications of systemic juvenile idiopathic arthritis: risk factors and management recommendations

Systemic juvenile idiopathic arthritis (SJIA) is an inflammatory condition characterized by fever, lymphadenopathy, arthritis, rash and serositis. Systemic inflammation has been associated with dysregulation of the innate immune system, suggesting that SJIA is an autoinflammatory disorder. IL-1 and IL-6 play a major role in the pathogenesis of SJIA, and treatment with IL-1 and IL-6 inhibitors has shown to be highly effective. However, complications of SJIA, including macrophage activation syndrome, limitations in functional outcome by arthritis and long-term damage from chronic inflammation, continue to be a major issue in SJIA patients' care. Translational research leading to a profound understanding of the cytokine crosstalk in SJIA and the identification of risk factors for SJIA complications will help to improve long-term outcome.

Macrophage Activation Syndrome in Patients with Systemic Juvenile Idiopathic Arthritis under Treatment with Tocilizumab

OBJECTIVE

To identify macrophage activation syndrome (MAS) in patients with systemic juvenile idiopathic arthritis (sJIA) undergoing tocilizumab (TCZ) treatment, and to confirm laboratory marker changes and responses to treatment in patients with MAS receiving TCZ.

METHODS

In Japan, 394 patients with sJIA were registered in an all-patient registry surveillance of TCZ as of January 15, 2012. TCZ (8 mg/kg) was administered every 2 weeks to patients with sJIA. MAS, hemophagocytic lymphohistiocytosis, or Epstein-Barr virus-associated hemophagocytic syndrome (EB-VAHS) was reported in 23 of these patients (25 events). The Safety Evaluation Committee of Tocilizumab for JIA reviewed these cases and clinically evaluated the data and laboratory findings using their own therapeutic experience. Events were categorized into 4 groups: definitive MAS, probable MAS, EB-VAHS, and non-MAS.

RESULTS

The committee's review revealed 3 events of definitive MAS in 3 patients, 12 events of probable MAS in 11 patients, 2 events of EB-VAHS in 2 patients, and 8 events of non-MAS in 8 patients. There were 2 patients who developed 2 events: 2 events in 1 patient were classified into definitive MAS and probable MAS, and 2 events in another patient were classified into probable MAS. In patients with definitive or probable MAS, common clinical manifestations and laboratory findings of MAS were observed. Changes in laboratory data observed in patients with EB-VAHS were similar to those observed in patients with MAS.

CONCLUSION

These results suggest that the clinical/laboratory features in the course of MAS appear to be similar among patients regardless of whether TCZ is administered. Similarities in the pathophysiological background of MAS and EB-VAHS were also suggested.

Reactive hemophagocytic syndrome in adult-onset Still disease: clinical features, predictive factors, and prognosis in 21 patients

Hemophagocytic syndrome (HPS) is a potentially life-threatening complication of systemic inflammatory disorders. Adult-onset Still disease (AOSD) is one of the systemic autoimmune diseases associated with reactive hemophagocytic syndrome (RHS). This study aimed to evaluate the characteristic findings, predictive factors, and prognosis of RHS in patients with AOSD. We retrospectively evaluated 109 patients diagnosed with AOSD and reviewed their clinical data and laboratory findings, including the biopsy results of 21 AOSD patients with RHS. Moreover, data from 17 hemophagocytic lymphohistiocytosis (HLH) patients evaluated during the same period were compared with those from the RHS patients. Twenty-one patients (19.3%) developed RHS during the course of AOSD, and only 7 patients (6.4%) were confirmed by bone marrow, liver, or lymph node biopsy. AOSD patients with RHS showed significantly higher frequencies of splenomegaly, hepatomegaly, and lymphadenopathy than did those without RHS. Moreover, patients with RHS showed significantly higher relapse rates than those without RHS (61.9% vs 18.2%, P < 0.001). Possible triggering factors inducing hemophagocytosis were detected in 16 of 21 RHS patients (76.2%): disease flare in 12 patients (75%), infection in 3 patients (18.8%), and drug use in 1 patient (6.3%). AOSD patients with RHS showed higher frequencies of leukopenia, anemia, thrombocytopenia, hypoalbuminemia, hypofibrinogenemia, hypertriglyceridemia, hyperferritinemia, and elevated lactate dehydrogenase levels than did those without RHS. Multivariate logistic regression with forward selection procedure showed that low platelet count (<121,000/mm³), anemia, and hepatomegaly were independent predictors of RHS. Patients with definite RHS and those with probable RHS showed comparable results. Although RHS is a life-threatening complication of AOSD, long-term prognosis was observed to be similar in patients with and those without RHS. Compared to RHS patients, HLH patients had poor prognosis, such as higher death rates (52.9% vs 9.5%, P = 0.005). RHS can be considered when an AOSD patient shows at least 2 of the following 3 findings: low platelet count, anemia, and hepatomegaly. Diagnostic confirmation by biopsy may not be essential if typical clinical findings of RHS are present. Moreover, prognosis of RHS was better than that of HLH diagnosed by the presence of trilineage cytopenia at admission.

Unusual clinical presentations of familial hemophagocytic lymphohistiocytosis type-2

BACKGROUND

Mutations of PRF1 gene have been identified in familial hemophagocytic lymphohistiocytosis type-2 (FHL-2) patients, and it has been reported as the commonest gene defect causing FHL. Patients with severe perforin deficiency usually present within first 1 year of life and with severe clinical manifestations.

OBSERVATION

We report 4 cases of severe perforin deficiency presenting with delayed onset and unusual clinical presentations viz., B-cell acute lymphoblastic leukemia, the Hodgkin lymphoma, tuberculosis, and the Still disease. Three of these 4 cases showed a common heterozygous missense mutation (p.Trp129Ser). Two of these patients expired because of uncontrolled hemophagocytic lymphohistiocytosis, one patient had 3 relapses while on therapy and one patient was in remission on maintenance therapy.

CONCLUSION

This study shows variety of clinical manifestations of perforin deficiency and although the onset of hemophagocytic lymphohistiocytosis is delayed in these patients, the outcome remains poor as in classical severe perforin deficiency patients.

Update on research and clinical translation on specific clinical areas: From bench to bedside: How insight in immune pathogenesis can lead to precision medicine of severe juvenile idiopathic arthritis

Despite the enormous progress in the treatment of juvenile idiopathic arthritis (JIA), innovations based on true bench-to-bedside research, performed in JIA patients, are still scarce. This chapter describes novel developments in which clinical innovations go hand in hand with basic discoveries. For the purpose of this review, we will mainly focus on developments in severe forms of JIA, most notably systemic JIA and polyarticular JIA. However, also in less severe forms of JIA, such as oligoarticular JIA, better insight will help to improve diagnosis and treatment. Facilitating the transition from bench to bedside will prove crucial for addressing the major challenges in JIA management. If successful, it will set new standards for a safe, targeted and personalized therapeutic approach for children with JIA.

Effectiveness of first-line treatment with recombinant interleukin-1 receptor antagonist in steroid-naive patients with new-onset systemic juvenile idiopathic arthritis: results of a prospective cohort study

OBJECTIVE

To conduct a prospective cohort study using anakinra, a recombinant IL-1 receptor antagonist (IL-1Ra), as first-line therapy in patients with new-onset systemic juvenile idiopathic arthritis (JIA).

METHODS

Therapy with recombinant IL-1Ra (2 mg/kg) was initiated in 20 patients who fulfilled the International League of Associations for Rheumatology criteria for systemic JIA, before systemic steroid treatment was administered. Patients were monitored clinically and immunologically. The protocol contained a stop strategy for patients who met at least the adapted American College of Rheumatology 90% criteria for improvement in JIA (ACR Pediatric 90 [ACR Pedi 90]) after 3 months.

RESULTS

We included consecutive patients with new-onset systemic JIA. The mean followup period was 32 months (range 12-54 months). At the 3-month time point, 85% of the patients showed an adapted ACR Pedi 90 response or had inactive disease; 75% of the patients achieved this response while receiving recombinant IL-1Ra alone. After 1 year, 17 of the 20 patients met the criteria for clinically inactive disease, and 13 of these patients met these criteria while receiving monotherapy with recombinant IL-1Ra. However, because of persistent disease activity, 7 of the 20 patients required additional therapy besides recombinant IL-1Ra. According to our stop strategy, 73% of patients with at least an adapted ACR Pedi 90 response at 3 months could stop recombinant IL-1Ra treatment within 1 year. After 2 years, 12 (86%) of 14 patients met the criteria for disease remission, either while receiving (n = 4) or not receiving (n = 8) medication. After 3 years, 10 (91%) of 11 patients met the criteria for disease remission, either while receiving (n = 2) or not receiving (n = 8) medication.

CONCLUSION

This is the first prospective study in which recombinant IL-1Ra was used as first-line therapy in patients with systemic JIA. We observed excellent responses in nearly all patients within 3 months. In the majority of responding patients, treatment with recombinant IL-1Ra could be stopped within 1 year, with remission being preserved during followup. In approximately one-third of patients, concomitant therapy was required for maintenance of clinical response.

Familial hemophagocytic lymphohistiocytosis: when rare diseases shed light on immune system functioning

The human immune system depends on the activity of cytotoxic T lymphocytes (CTL), natural killer (NK) cells, and NKT cells in order to fight off a viral infection. Understanding the molecular mechanisms during this process and the role of individual proteins was greatly improved by the study of familial hemophagocytic lymphohistiocytosis (FHL). Since 1999, genetic sequencing is the gold standard to classify patients into different subgroups of FHL. The diagnosis, once based on a clinical constellation of abnormalities, is now strongly supported by the results of a functional flow-cytometry screening, which directs the genetic study. A few additional congenital immune deficiencies can also cause a resembling or even identical clinical picture to FHL. As in many other rare human disorders, the collection and analysis of a relatively large number of cases in registries is crucial to draw a complete picture of the disease. The conduction of prospective therapeutic trials allows investigators to increase the awareness of the disease and to speed up the diagnostic process, but also provides important functional and genetic confirmations. Children with confirmed diagnosis may undergo hematopoietic stem cell transplantation, which is the only cure known to date. Moreover, detailed characterization of these rare patients helped to understand the function of individual proteins within the exocytic machinery of CTL, NK, and NKT cells. Moreover, identification of these genotypes also provides valuable information on variant phenotypes, other than FHL, associated with biallelic and monoallelic mutations in the FHL-related genes. In this review, we describe how detailed characterization of patients with genetic hemophagocytic lymphohistiocytosis has resulted in improvement in knowledge regarding contribution of individual proteins to the functional machinery of cytotoxic T- and NK-cells. The review also details how identification of these genotypes has provided valuable information on variant phenotypes.

Adult-onset Still's disease

First described in 1971, adult-onset Still's disease (AOSD) is a rare multisystemic disorder considered as a complex (multigenic) autoinflammatory syndrome. A genetic background would confer susceptibility to the development of autoinflammatory reactions to environmental triggers. Macrophage and neutrophil activation is a hallmark of AOSD which can lead to a reactive hemophagocytic lymphohistiocytosis. As in the latter disease, the cytotoxic function of natural killer cells is decreased in patients with active AOSD. IL-18 and IL-1β, two proinflammatory cytokines processed through the inflammasome machinery, are key factors in the pathogenesis of AOSD; they cause IL-6 and Th1 cytokine secretion as well as NK cell dysregulation leading to macrophage activation. The clinico-biological picture of AOSD usually includes high spiking fever with joint symptoms, evanescent skin rash, sore throat, striking neutrophilic leukocytosis, hyperferritinemia with collapsed glycosylated ferritin (<20%), and abnormal liver function tests. According to the clinical presentation of the disease at diagnosis, two AOSD phenotypes may be distinguished: i) a highly symptomatic, systemic and feverish one, which would evolve into a systemic (mono- or polycyclic) pattern; ii) a more indolent one with arthritis in the foreground and poor systemic symptomatology, which would evolve into a chronic articular pattern. Steroid- and methotrexate-refractory AOSD cases benefit now from recent insights into autoinflammatory disorders: anakinra seems to be an efficient, well tolerated, steroid-sparing treatment in systemic patterns; tocilizumab seems efficient in AOSD with active arthritis and systemic symptoms while TNFα-blockers could be interesting in chronic polyarticular refractory AOSD.

Natural killer cell activity and frequency of killer cell immunoglobulin-like receptors in children with different forms of juvenile idiopathic arthritis

BACKGROUND

Juvenile idiopathic arthritis (JIA) has three major onset types with widely varying clinical features: systemic, polyarticular and pauciarticular. We assessed natural killer (NK) cell function and killer cell immunoglobulin-like receptor (KIR) genotypes in patients with different JIA subtypes.

METHODS

Peripheral blood samples from 72 children with active JIA (systemic, 25; polyarticular, 24; pauciarticular, 23) and 25 controls were used for flow cytometric assessments of NK cell count, cytotoxicity, perforin, granzyme B, interferon (IFN)-γ and tumour necrosis factor (TNF)-α. Samples from 220 children with JIA (systemic, 84; polyarticular, 72; pauciarticular, 64) and 150 controls were used for KIR2DS2, KIR2DS4, KIR3DS1, KIR2DL1, KIR2DL2, KIR2DL3 and KIR3DL1 typing by polymerase chain reaction with sequence-specific oligonucleotide probes.

RESULTS

Compared with the controls, the patients with systemic JIA showed lower NK cell counts, cytotoxicity and perforin and granzyme B expression (p < 0.05), while the patients with pauci- and polyarticular JIA showed higher perforin and granzyme B expression (p < 0.05). NK cells produced higher level of TNF-α while lower level of IFN-γ in the pauci- and polyarticular JIA groups than in the systemic JIA group (p < 0.05). No significant differences in KIR gene frequencies were found between the JIA subgroups and healthy controls, except for the positive frequency and locus frequency of KIR2DS4, which were lower in the systemic JIA group.

CONCLUSIONS

Compared with poly- and pauciarticular JIA, systemic JIA is associated with decreased NK cell function, more IFN-γ and less TNF-α secretion of NK cell and lower KIR2DS4 frequency.

Natural killer cells in human autoimmune disorders

Natural killer (NK) cells are innate lymphocytes that play a critical role in early host defense against viruses. Through their cytolytic capacity and generation of cytokines and chemokines, NK cells modulate the activity of other components of the innate and adaptive immune systems and have been implicated in the initiation or maintenance of autoimmune responses. This review focuses on recent research elucidating a potential immunoregulatory role for NK cells in T-cell and B-cell-mediated autoimmune disorders in humans, with a particular focus on multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematous. A better understanding of the contributions of NK cells to the development of autoimmunity may lead to novel therapeutic targets in these diseases.

Successful treatment of macrophage activation syndrome complicating adult Still disease with anakinra

A previously healthy 20-year-old man presented with adult Still disease (ASD). He developed life-threatening macrophage activation syndrome (MAS), which was refractory to standard immunosuppression but responded dramatically to the IL-1 receptor antagonist anakinra. Subsequent immunological investigations included assessment of the perforin expression of natural killer (NK) cells and CD8+ T cells, which confirmed MAS.

Natural killer T cell deficiency in active adult-onset Still's Disease: correlation of deficiency of natural killer T cells with dysfunction of natural killer cells

OBJECTIVE

To examine the levels and functions of natural killer (NK) and natural killer T (NKT) cells, investigate relationships between NK and NKT cells, and determine the clinical relevance of NKT cell levels in patients with adult-onset Still's disease (AOSD).

METHODS

Patients with active untreated AOSD (n = 20) and age- and sex-matched healthy controls (n = 20) were studied. NK and NKT cell levels were measured by flow cytometry. Peripheral blood mononuclear cells were cultured in vitro with α-galactosylceramide (αGalCer). NK cytotoxicity against K562 cells and proliferation indices of NKT cells were estimated by flow cytometry.

RESULTS

Percentages and absolute numbers of NKT cells were significantly lower in the peripheral blood of AOSD patients than in that of healthy controls. Proliferative responses of NKT cells to αGalCer were also lower in patients, and this was found to be due to proinflammatory cytokines and NKT cell apoptosis. In addition, NK cytotoxicity was found to be significantly lower in patients than in healthy controls, but NK cell levels were comparable in the 2 groups. Notably, this NKT cell deficiency was found to be correlated with NK cell dysfunction and to reflect active disease status. Furthermore, αGalCer-mediated NK cytotoxicity, showing the interaction between NK and NKT cells, was significantly lower in AOSD patients than in healthy controls.

CONCLUSION

These findings demonstrate that NK and NKT cell functions are defective in AOSD patients and suggest that these abnormalities contribute to innate immune dysfunction in AOSD.

Correlation analyses of clinical and molecular findings identify candidate biological pathways in systemic juvenile idiopathic arthritis

BACKGROUND

Clinicians have long appreciated the distinct phenotype of systemic juvenile idiopathic arthritis (SJIA) compared to polyarticular juvenile idiopathic arthritis (POLY). We hypothesized that gene expression profiles of peripheral blood mononuclear cells (PBMC) from children with each disease would reveal distinct biological pathways when analyzed for significant associations with elevations in two markers of JIA activity, erythrocyte sedimentation rate (ESR) and number of affected joints (joint count, JC).

METHODS

PBMC RNA from SJIA and POLY patients was profiled by kinetic PCR to analyze expression of 181 genes, selected for relevance to immune response pathways. Pearson correlation and Student's t-test analyses were performed to identify transcripts significantly associated with clinical parameters (ESR and JC) in SJIA or POLY samples. These transcripts were used to find related biological pathways.

RESULTS

Combining Pearson and t-test analyses, we found 91 ESR-related and 92 JC-related genes in SJIA. For POLY, 20 ESR-related and 0 JC-related genes were found. Using Ingenuity Systems Pathways Analysis, we identified SJIA ESR-related and JC-related pathways. The two sets of pathways are strongly correlated. In contrast, there is a weaker correlation between SJIA and POLY ESR-related pathways. Notably, distinct biological processes were found to correlate with JC in samples from the earlier systemic plus arthritic phase (SAF) of SJIA compared to samples from the later arthritis-predominant phase (AF). Within the SJIA SAF group, IL-10 expression was related to JC, whereas lack of IL-4 appeared to characterize the chronic arthritis (AF) subgroup.

CONCLUSIONS

The strong correlation between pathways implicated in elevations of both ESR and JC in SJIA argues that the systemic and arthritic components of the disease are related mechanistically. Inflammatory pathways in SJIA are distinct from those in POLY course JIA, consistent with differences in clinically appreciated target organs. The limited number of ESR-related SJIA genes that also are associated with elevations of ESR in POLY implies that the SJIA associations are specific for SJIA, at least to some degree. The distinct pathways associated with arthritis in early and late SJIA raise the possibility that different immunobiology underlies arthritis over the course of SJIA.

Natural Killer Cell Cytolytic Function in Korean Patients with Adult-onset Still’s Disease

Objective.

To investigate natural killer (NK) cell proportions, NK cell cytotoxicity, and interleukin 18 (IL-18) expression, in patients with adult-onset Still’s disease (AOSD).

Methods.

Forty-five patients with AOSD (active = 22, inactive = 23) and 32 healthy controls were included. The proportions of NK cells among peripheral blood mononuclear cells were assessed by flow cytometry. IL-18 and IL-18-binding protein (IL-18BP) concentrations were measured by ELISA. Twenty-four patients with AOSD and 18 controls were examined for cytotoxic activity of NK cells by co-incubating NK cells with NK-sensitive K562 cells. The association of NK cell function with clinical and laboratory measures was investigated.

Results.

The proportions of NK cells were significantly lower in patients with active AOSD than in patients with inactive disease and controls. NK cell cytotoxic function was significantly lower in patients with AOSD than in controls. NK cell proportions and cytotoxic functions were reexamined in 11 and 6 patients, respectively, after treatment. Low NK cell proportion and cytotoxic dysfunction were improved with clinical improvements of the patients. IL-18 and IL-18BP levels were much higher in patients with active AOSD than in controls. NK cell cytotoxic functions were consistently low and IL-18 and IL-18BP levels were constantly high in patients with AOSD, regardless of disease activity.

Conclusion.

Low NK cell proportion, defective cytotoxic function, and elevated IL-18 levels may be significant features of AOSD. After resolution of the acute phase, low NK cell proportion was recovered and NK cell cytolytic function was restored along with clinical improvement. These findings possibly contribute to immunologic abnormalities in AOSD.

Familial and acquired hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome in which an uncontrolled and ineffective immune response, triggered in most cases by infectious agents, leads to severe hyperinflammation. Familial forms of HLH (FHL), which are increasingly found also in adolescents and adults, are due to genetic defects leading to impaired function of natural killer cells and cytotoxic T cells. These mutations occur either in the perforin gene or in genes important for the exocytosis of cytotoxic granules. Cytotoxic granules contain perforin and granzymes, which induce apoptosis upon entering (infected) target cells. Additionally, perforin is important for the downregulation of the immune response. Acquired forms of HLH are encountered in association with (usually) viral infections, autoinflammatory/autoimmune diseases, malignant diseases, and acquired immune deficiency states (e.g., after organ transplantation). Treatment of HLH includes immune-suppressive and immune-modulatory agents, cytostatic drugs, and biological response modifiers. For patients with FHL, stem cell transplantation is indicated and can be curative.

Juvenile idiopathic arthritis

Juvenile idiopathic arthritis is a heterogeneous group of diseases characterised by arthritis of unknown origin with onset before age of 16 years. Pivotal studies in the past 5 years have led to substantial progress in various areas, ranging from disease classification to new treatments. Gene expression profiling studies have identified different immune mechanisms in distinct subtypes of the disease, and can help to redefine disease classification criteria. Moreover, immunological studies have shown that systemic juvenile idiopathic arthritis is an acquired autoinflammatory disease, and have led to successful studies of both interleukin-1 and interleukin-6 blockade. In other forms of the disease, synovial inflammation is the consequence of a disturbed balance between proinflammatory effector cells (such as T-helper-17 cells), and anti-inflammatory regulatory cells (such as FOXP3-positive regulatory T cells). Moreover, specific soluble biomarkers (S100 proteins) can guide individual treatment. Altogether these new developments in genetics, immunology, and imaging are instrumental to better define, classify, and treat patients with juvenile idiopathic arthritis.

Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions

Systemic juvenile idiopathic arthritis (sJIA) has long been recognized as unique among childhood arthritides, because of its distinctive clinical and epidemiological features, including an association with macrophage activation syndrome. Here, we summarize research into sJIA pathogenesis. The triggers of disease are unknown, although infections are suspects. Once initiated, sJIA seems to be driven by innate proinflammatory cytokines. Endogenous Toll-like receptor ligands, including S100 proteins, probably synergize with cytokines to perpetuate inflammation. These and other findings support the hypothesis that sJIA is an autoinflammatory condition. Indeed, IL-1 is implicated as a pivotal cytokine, but the source of excess IL-1 activity remains obscure and the role of IL-1 in chronic arthritis is less clear. Another hypothesis is that a form of hemophagocytic lymphohistiocytosis underlies sJIA, with varying degrees of its expression across the spectrum of disease. Alternatively, sJIA with MAS might be a genetically distinct subtype. Yet another hypothesis proposes that inadequate downregulation of immune activation is central to sJIA, supporting evidence for which includes 'alternative activation' of monocyte and macrophages and possible deficiencies in IL-10 and T regulatory cells. Some altered immune phenotypes persist during clinically inactive disease, which suggests that this stage might represent compensated inflammation. Despite much progress being made, many questions remain, providing fertile ground for future research.

Autologous hematopoietic stem cell transplantation in autoimmune diseases

The term 'autoimmune diseases' encompasses a spectrum of diseases whose clinical manifestations and, possibly, biological features vary widely. The results of conventional treatment are considered unsatisfactory in aggressive forms, with subsets of patients having short life expectancies. Relying on wide experimental evidence and more feeble clinical data, some research groups have used autologous hematopoietic stem cell transplantation (HSCT) in the most disabling autoimmune diseases with the aim of resetting the patient's immune system. Immunoablative conditioning regimens are preferred over their myeloablative counterparts, and some form of in vivo and/or ex vivo T-cell depletion is generally adopted. Despite 15 years' experience, published controlled clinical trials are still lacking, with the evidence so far available coming from pilot studies and registry surveys. In multiple sclerosis, clinical improvement, or at least lasting disease stabilization, can be achieved in the majority of the patients; nevertheless, the worst results are observed in patients with progressive disease, where no benefit can be expected from conventional therapy. Concerning rheumatologic diseases, wide experience has been acquired in systemic sclerosis, with long-term improvements in cutaneous disease being frequently reported, although visceral involvement remains unchanged at best. Autografting has proved to be barely effective in rheumatoid arthritis and quite toxic in juvenile idiopathic arthritis, whereas it leads to clinical remission and the reversal of visceral impairment in the majority of patients with systemic lupus erythematosus. A promising indication is Crohn's disease, in which long-term endoscopic remission is frequently observed. Growing experience with autologous HCST in autoimmune diseases has progressively reduced concerns about transplant-related mortality and secondary myelodysplasia/leukemia. Therefore, a sustained complete remission seems to be within the reach of autografting in some autoimmune diseases; in others, the indications, risks and benefits of autografting need to be better defined. Consequently, the search for new drugs should also be encouraged.

Pathogenesis and clinical manifestations of juvenile rheumatoid arthritis

Juvenile rheumatoid arthritis (JRA) is the most common rheumatic childhood disease; its onset is before 16 years of age and it persists for at least 6 weeks. JRA encompasses a heterogeneous group of diseases that is classified according to 3 major presentations: oligoarthritis, polyarthritis, and systemic onset diseases. These presentations may originate from the same or different causes that involve interaction with specific immunogenetic predispositions, and result in heterogeneous clinical manifestations. An arthritic joint exhibits cardinal signs of joint inflammation, such as swelling, pain, heat, and loss of function; any joint can be arthritic, but large joints are more frequently affected. Extra-articular manifestations include high fever, skin rash, serositis, and uveitis. The first 2 types of JRA are regarded as T helper 1 (Th1) cell-mediated inflammatory disorders, mainly based on the abundance of activated Th1 cells in the inflamed synovium and the pathogenetic role of proinflammatory cytokines that are mainly produced by Th1 cell-stimulated monocytes. In contrast, the pathogenesis of systemic onset disease differs from that of other types of JRA in several respects, including the lack of association with human leukocyte antigen type and the absence of autoantibodies or autoreactive T cells. Although the precise mechanism that leads to JRA remains unclear, proinflammatory cytokines are thought to be responsible for at least part of the clinical symptoms in all JRA types. The effectiveness of biologic therapy in blocking the action of these cytokines in JRA patients provides strong evidence that they play a fundamental role in JRA inflammation.

Macrophage activation syndrome: advances towards understanding pathogenesis

PURPOSE OF REVIEW

Macrophage activation syndrome (MAS), a major cause of morbidity and mortality in pediatric rheumatology, is most strongly associated with systemic juvenile idiopathic arthritis (SJIA). There are no validated diagnostic criteria and early diagnosis is difficult. This review summarizes the progress in understanding of MAS pathophysiology that may help define specific diagnostic biomarkers.

RECENT FINDINGS

MAS is similar to the autosomal recessive disorders collectively known as familial hemophagocytic lymphohistiocytosis (FHLH), all associated with various genetic defects affecting the cytolytic pathway. Cytolytic function is profoundly depressed in SJIA with MAS as well. This immunologic abnormality distinguishes SJIA from other rheumatic diseases and is caused by both genetic and acquired factors. Phenotypic characterization of hemophagocytic macrophages has been another focus of research. These macrophages express CD163, a scavenger receptor that binds hemoglobin-haptoglobin complexes, and initiate pathways important for adaptation to oxidative stress induced by free iron. Expansion of these macrophages is seen in more than 30% of SJIA patients perhaps representing early stages of MAS. Recent gene expression studies linked expansion of these macrophages to distinct signatures.

SUMMARY

Recent advances in understanding of pathophysiologic conditions that favor expansion of hemophagocytic macrophages provide a source of new MAS biomarkers with applicability to clinical practice.

Natural killer cells: versatile roles in autoimmune and infectious diseases

Natural killer (NK) cells are essential members of innate immunity and they rapidly respond to a variety of insults via cytokine secretion and cytolytic activity. Effector functions of NK cells form an important first line of innate immunity against viral, bacterial and parasitic infections, as well as an important bridge for the activation of adaptive immune responses. The control of NK-cell activation and killing is now understood to be a highly complex system of diverse inhibitory and activatory receptor-ligand interactions, sensing changes in MHC expression. NK cells have a functional role in innate immunity as the primary source of NK-cell-derived immunoregulatory cytokines, which have been identified in target organs of patients suffering from autoimmune diseases, and play a critical role in early defense against infectious agents. This review focuses on recent research of NK cells, summarizing their potential immunoregulatory role in modulating autoimmunity and infectious diseases.