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

Pathogenesis of Hemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome: A Case Report and Review of the Literature

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition characterized by the uncontrolled activation of cytotoxic T lymphocytes, NK cells, and macrophages, resulting in an overproduction of pro-inflammatory cytokines. A primary and a secondary form are distinguished depending on whether or not it is associated with hematologic, infectious, or immune-mediated disease. Clinical manifestations include fever, splenomegaly, neurological changes, coagulopathy, hepatic dysfunction, cytopenia, hypertriglyceridemia, hyperferritinemia, and hemophagocytosis. In adults, therapy, although aggressive, is often unsuccessful. We report the case of a 41-year-old man with no apparent history of previous disease and an acute onset characterized by fever, fatigue, and weight loss. The man was from Burkina Faso and had made trips to his home country in the previous five months. On admission, leukopenia, thrombocytopenia, increased creatinine and transaminases, LDH, and CRP with a normal ESR were found. The patient also presented with hypertriglyceridemia and hyperferritinemia. An infectious or autoimmune etiology was ruled out. A total body CT scan showed bilateral pleural effusion and hilar mesenterial, abdominal, and paratracheal lymphadenopathy. Lymphoproliferative disease with HLH complication was therefore suspected. High doses of glucocorticoids were then administered. A cytologic analysis of the pleural effusion showed anaplastic lymphoma cells and bone marrow aspirate showed hemophagocytosis. An Epstein-Barr Virus (EBV) DNA load of more than 90000 copies/mL was found. Bone marrow biopsy showed a marrow localization of peripheral T lymphoma. The course was rapidly progressive until the patient died. HLH is a rare but usually fatal complication in adults of hematologic, autoimmune, and malignant diseases. Very early diagnosis and treatment are critical but not always sufficient to save patients.

The 4th NextGen Therapies for SJIA and MAS: part 1 the elephant in the room: diagnostic/classification criteria for systemic juvenile idiopathic arthritis and adult-onset still's disease

Currently, the criteria used to classify patients with SJIA are different from those used for AOSD. However, it has been recognized that the existing terms are too narrow, subdividing the Still's population unnecessarily between pediatric-onset and adult-onset disease and excluding an appreciable group of children in whom overt arthritis is delayed or absent. Government regulators and insurers rely upon the guidance of subject experts to provide disease definitions, and when these definitions are flawed, to provide new and better ones. The classification session at the NextGen 2022 conference helped to serve this purpose, establishing the need for a revised definitional system that transcends the fault lines that remain in existing definitions.

Murine Models of Secondary Cytokine Storm Syndromes

Hemophagocytic lymphohistiocytosis (HLH) comprises a broad spectrum of life-threatening cytokine storm syndromes, classified into primary (genetic) or secondary (acquired) HLH. The latter occurs in a variety of medical conditions, including infections, malignancies, autoimmune and autoinflammatory diseases, acquired immunodeficiency, and metabolic disorders. Despite recent advances in the field, the pathogenesis of secondary HLH remains incompletely understood. Considering the heterogeneity of triggering factors and underlying diseases in secondary HLH, a large diversity of animal models has been developed to explore pivotal disease mechanisms. To date, over 20 animal models have been described that each recapitulates certain aspects of secondary HLH. This review provides a comprehensive overview of the existing models, highlighting relevant findings, discussing the involvement of different cell types and cytokines in disease development and progression, and considering points of interest toward future therapeutic strategies.

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.

Genetics of Macrophage Activation Syndrome in Systemic Juvenile Idiopathic Arthritis

Macrophage activation syndrome (MAS) is a life-threatening episode of hyperinflammation driven by excessive activation and expansion of T cells (mainly CD8) and hemophagocytic macrophages producing proinflammatory cytokines. MAS has been reported in association with almost every rheumatic disease, but it is by far most common in systemic juvenile idiopathic arthritis (SJIA). Clinically, MAS is similar to familial or primary hemophagocytic lymphohistiocytosis (pHLH), a group of rare autosomal recessive disorders linked to various genetic defects all affecting the perforin-mediated cytolytic pathway employed by NK cells and cytotoxic CD8 T lymphocytes. Decreased cytolytic activity in pHLH patients leads to prolonged survival of target cells associated with increased production of proinflammatory cytokines that overstimulate macrophages. The resulting cytokine storm is believed to be responsible for the frequently fatal multiorgan system failure seen in MAS. Whole exome sequencing as well as targeted sequencing of pHLH-associated genes in patients with SJIA-associated MAS demonstrated increased "burden" of rare protein-altering variants affecting the cytolytic pathway compared to healthy controls, suggesting that as in pHLH, genetic variability in the cytolytic pathway contributes to MAS predisposition. Functional studies of some of the novel variants have shown that even in a heterozygous state, their presence partially reduces cytolytic activity that may lead to increased cytokine production.

Cytokine Storm Syndrome Associated with Systemic Juvenile Idiopathic Arthritis

The cytokine storm syndrome (CSS) associated with systemic juvenile idiopathic arthritis (sJIA) has widely been referred to as macrophage activation syndrome (MAS). In this chapter, we use the term sJIA-associated CSS (sJIA-CSS) when referring to this syndrome and use the term MAS when referencing publications that specifically report on sJIA-associated MAS.

Etoposide Therapy of Cytokine Storm Syndromes

Etoposide has revolutionized the treatment of primary as well as secondary hemophagocytic lymphohistiocytosis (HLH), and it is, together with corticosteroids, the most widely used therapy for HLH. In the early 1980s, long-term survival in primary HLH was <5% but with the etoposide-/dexamethasone-based protocols HLH-94 and HLH-2004, in combination with stem cell transplantation, 5-year survival increased dramatically to around 60% in primary HLH, and based on analyses from the HLH-2004 study, there is likely room for further improvement. Biologically, etoposide administration results in potent selective deletion of activated T cells as well as efficient suppression of inflammatory cytokine production. Moreover, etoposide has also been reported to promote programmed cell death (apoptosis) rather than proinflammatory lytic cell death (pyroptosis), conceivably ameliorating subsequent systemic inflammation, i.e., a treatment very suitable for cytokine storm syndromes (CSS). The combination of etoposide and corticosteroids may also be beneficial in cases of severe or refractory secondary HLH (sHLH) with imminent organ failure, such as infection-associated HLH caused by Epstein-Barr virus (EBV) or malignancy-triggered HLH. In CSS associated with rheumatic diseases (macrophage activation syndrome, MAS or MAS-HLH), etoposide is currently used as second- or third-line therapy. Recent studies suggest that etoposide perhaps should be part of an aggressive therapeutic intervention for patients with severe refractory or relapsing MAS, in particular if there is CNS involvement. Importantly, awareness of sHLH must be further increased since treatment of sHLH is often delayed, thereby missing the window of opportunity for a timely, effective, and potentially life-saving HLH-directed treatment.

Complementary HLH susceptibility factors converge on CD8 T-cell hyperactivation

Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening hyperinflammatory syndromes. Familial HLH is caused by genetic impairment of granule-mediated cytotoxicity (eg, perforin deficiency). MAS is linked to excess activity of the inflammasome-activated cytokine interleukin-18 (IL-18). Though individually tolerated, mice with dual susceptibility (Prf1⁻/⁻Il18tg; DS) succumb to spontaneous, lethal hyperinflammation. We hypothesized that understanding how these susceptibility factors synergize would uncover key pathomechanisms in the activation, function, and persistence of hyperactivated CD8 T cells. In IL-18 transgenic (Il18tg) mice, IL-18 effects on CD8 T cells drove MAS after a viral (lymphocytic choriomeningitis virus), but not innate (toll like receptor 9), trigger. In vitro, CD8 T cells also required T-cell receptor (TCR) stimulation to fully respond to IL-18. IL-18 induced but perforin deficiency impaired immunoregulatory restimulation-induced cell death (RICD). Paralleling hyperinflammation, DS mice displayed massive postthymic oligoclonal CD8 T-cell hyperactivation in their spleens, livers, and bone marrow as early as 3 weeks. These cells increased proliferation and interferon gamma production, which contrasted with increased expression of receptors and transcription factors associated with exhaustion. Broad-spectrum antibiotics and antiretrovirals failed to ameliorate the disease. Attempting to genetically "fix" TCR antigen-specificity instead demonstrated the persistence of spontaneous HLH and hyperactivation, chiefly on T cells that had evaded TCR fixation. Thus, drivers of HLH may preferentially act on CD8 T cells: IL-18 amplifies activation and demand for RICD, whereas perforin supplies critical immunoregulation. Together, these factors promote a terminal CD8 T-cell activation state, combining features of exhaustion and effector function. Therefore, susceptibility to hyperinflammation may converge on a unique, unrelenting, and antigen-dependent state of CD8 T-cell hyperactivation.

IL-18 in Autoinflammatory Diseases: Focus on Adult Onset Still Disease and Macrophages Activation Syndrome

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine that is involved in various innate and adaptive immune processes related to infection, inflammation, and autoimmunity. Therefore, it is described as a key mediator of autoinflammatory diseases associated with the development of macrophage activation syndrome (MAS), including systemic juvenile idiopathic arthritis and adult-onset Still's disease. This review focuses on the role of IL-18 in inflammatory responses, placing emphasis on autoinflammatory diseases associated with chronic excess of serum IL-18, which correlate with clinical and biological signs of the disease. Therefore, it is useful for the diagnosis and monitoring of disease activity. Researchers are currently investigating IL-18's role as a therapeutic target for the treatment of inflammatory diseases. The inhibition of IL-18 signaling through recombinant human IL-18BP (IL-18 binding protein) seems to be an effective therapeutic strategy, though further studies are necessary to clarify its importance as a therapeutic target.

Bispecific NK-cell engager targeting BCMA elicits stronger antitumor effects and produces less proinflammatory cytokines than T-cell engager

Bispecific antibodies have attracted more attention in recent years for the treatment of tumors, in which most of them target CD3, which mediates the killing of tumor cells by T cells. However, T-cell engager may cause serious side effects, including neurotoxicity and cytokine release syndrome. More safe treatments are still needed to address unmet medical needs, and NK cell-based immunotherapy is a safer and more effective way to treat tumors. Our study developed two IgG-like bispecific antibodies with the same configuration: BT1 (BCMA×CD3) attracted T cells and tumor cells, while BK1 (BCMA×CD16) attracted NK cells and tumor cells. Our study showed that BK1 mediated NK cell activation and upregulated the expression of CD69, CD107a, IFN-γ and TNF. In addition, BK1 elicited a stronger antitumor effect than BT1 both in vitro and in vivo. Combinatorial treatment (BK1+BT1) showed a stronger antitumor effect than either treatment alone, as indicated by in vitro experiments and in vivo murine models. More importantly, BK1 induced fewer proinflammatory cytokines than BT1 both in vitro and in vivo. Surprisingly, BK1 reduced cytokine production in the combinatorial treatment, suggesting the indispensable role of NK cells in the control of cytokine secretion by T cells. In conclusion, our study compared NK-cell engagers and T-cell engagers targeting BCMA. The results indicated that NK-cell engagers were more effective with less proinflammatory cytokine production. Furthermore, the use of NK-cell engagers in combinatorial treatment helped to reduce cytokine secretion by T cells, suggesting a bright future for NK-cell engagers in clinical settings.

Mouse models of systemic juvenile idiopathic arthritis and macrophage activation syndrome

Macrophage activation syndrome (MAS) is a life-threatening complication of pediatric rheumatic diseases, occurring most commonly in children with systemic juvenile idiopathic arthritis (SJIA). Despite several classes of currently available treatment options for SJIA, including biologic agents targeting IL-1 or IL-6, there remain severe cases suffering from refractory disease and recurrent MAS. The phenotype of MAS is similar to hemophagocytic lymphohistiocytosis (HLH), but the underlying pathophysiology of MAS complicating SJIA or other disorders has not been fully clarified. These facts make it challenging to develop and utilize animal models to study MAS. To date, there is no "perfect" model replicating MAS, but several models do demonstrate aspects of SJIA and/or MAS. In this review, we examine the proposed animal models of SJIA and MAS, focusing on how they reflect these disorders, what we have learned from the models, and potential future research questions. As we better understand the key features of each, animal models can be powerful tools to further define the pathophysiology of SJIA and MAS, and develop new treatment targets and strategies.

Biomarkers in Systemic Juvenile Idiopathic Arthritis, Macrophage Activation Syndrome and Their Importance in COVID Era

Systemic juvenile idiopathic arthritis (sJIA) and its complication, macrophage activation syndrome (sJIA-MAS), are rare but sometimes very serious or even critical diseases of childhood that can occasionally be characterized by nonspecific clinical signs and symptoms at onset-such as non-remitting high fever, headache, rash, or arthralgia-and are biologically accompanied by an increase in acute-phase reactants. For a correct positive diagnosis, it is necessary to rule out bacterial or viral infections, neoplasia, and other immune-mediated inflammatory diseases. Delays in diagnosis will result in late initiation of targeted therapy. A set of biomarkers is useful to distinguish sJIA or sJIA-MAS from similar clinical entities, especially when arthritis is absent. Biomarkers should be accessible to many patients, with convenient production and acquisition prices for pediatric medical laboratories, as well as being easy to determine, having high sensitivity and specificity, and correlating with pathophysiological disease pathways. The aim of this review was to identify the newest and most powerful biomarkers and their synergistic interaction for easy and accurate recognition of sJIA and sJIA-MAS, so as to immediately guide clinicians in correct diagnosis and in predicting disease outcomes, the response to treatment, and the risk of relapses. Biomarkers constitute an exciting field of research, especially due to the heterogeneous nature of cytokine storm syndromes (CSSs) in the COVID era. They must be selected with utmost care-a fact supported by the increasingly improved genetic and pathophysiological comprehension of sJIA, but also of CSS-so that new classification systems may soon be developed to define homogeneous groups of patients, although each with a distinct disease.

Interleukin-18 Binding Protein in Immune Regulation and Autoimmune Diseases

Natural soluble antagonist and decoy receptor on the surface of the cell membrane are evolving as crucial immune system regulators as these molecules are capable of recognizing, binding, and neutralizing (so-called inhibitors) their targeted ligands. Eventually, these soluble antagonists and decoy receptors terminate signaling by prohibiting ligands from connecting to their receptors on the surface of cell membrane. Interleukin-18 binding protein (IL-18BP) participates in regulating both Th1 and Th2 cytokines. IL-18BP is a soluble neutralizing protein belonging to the immunoglobulin (Ig) superfamily as it harbors a single Ig domain. The Ig domain is essential for its binding to the IL-18 ligand and holds partial homology to the IL-1 receptor 2 (IL-1R2) known as a decoy receptor of IL-1α and IL-1β. IL-18BP was defined as a unique soluble IL-18BP that is distinct from IL-18Rα and IL-18Rβ chain. IL-18BP is encoded by a separated gene, contains 8 exons, and is located at chr.11 q13.4 within the human genome. In this review, we address the difference in the biological activity of IL-18BP isoforms, in the immunity balancing Th1 and Th2 immune response, its critical role in autoimmune diseases, as well as current clinical trials of recombinant IL-18BP (rIL-18BP) or equivalent.

Infection-Triggered Hyperinflammatory Syndromes in Children

An association between infectious diseases and macrophage activation syndrome (MAS) has been reported, yet the exact role of infection in MAS development is still unclear. Here, a retrospective analysis of the clinical records of patients with rheumatic diseases complicated with MAS who were treated in a pediatric tertiary care center between 2011 and 2020 was performed. Any infection documented within the 30 days preceding the onset of MAS was reported. Out of 125 children in follow-up for systemic rheumatic diseases, 12 developed MAS, with a total of 14 episodes. One patient experienced three episodes of MAS. Clinical and/or laboratory evidence of infection preceded the onset of MAS in 12 events. Clinical features, therapeutic strategies, and patient outcomes were described. The aim of this study was to evaluate the possible role of infection as a relevant trigger for MAS development in children with rheumatic conditions. The pathogenetic pathways involved in the cross-talk between uncontrolled inflammatory activity and the immune response to infection deserve further investigation.

Pathogenesis and Treatment of Refractory Disease Courses in Systemic Juvenile Idiopathic Arthritis: Refractory Arthritis, Recurrent Macrophage Activation Syndrome and Chronic Lung Disease

Systemic juvenile idiopathic arthritis is a distinct and heterogeneous disease presently classified under the umbrella of juvenile idiopathic arthritis, with some patients following a monophasic remitting course, whereas others have persistent disease with chronic organ- and life-threatening complications. Although biologic therapies have revolutionized treatment, recent follow-up studies report significant numbers of children with persistently active disease on long term follow-up. This review focuses on refractory disease courses, specifically refractory arthritis, systemic juvenile idiopathic arthritis with recurrent, or longstanding signs of macrophage activation syndrome, and systemic juvenile idiopathic arthritis associated with suspected, probable, or definite lung disease.

Hemophagocytic Lymphohistiocytosis

CONTEXT.—

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder of immune regulation that can eventually result in end-organ damage and death. HLH is characterized by uncontrolled activation of cytotoxic T lymphocytes, natural killer cells, and macrophages that can lead to a cytokine storm. The diagnosis of HLH is often challenging due to the diverse clinical manifestations and the presence of several diagnostic mimics. The prognosis is generally poor, warranting rapid diagnosis and aggressive management.

OBJECTIVE.—

To provide a comprehensive review of the pathogenesis, clinical features, diagnosis, and management of HLH.

DATA SOURCES.—

Peer-reviewed literature.

CONCLUSIONS.—

HLH is a condition where a complete understanding of the pathogenesis, early diagnosis, and proper management has an important role in determining patient outcome. Genetic mutations causing impairment in the function of cytotoxic T lymphocytes and natural killer cells have been identified as the root cause of familial HLH; however, the specific pathogenesis of acquired HLH is unclear. The HLH-2004 protocol used in the diagnosis of HLH was originally developed for the pediatric population. The HLH-2004 protocol still forms the basis of the diagnosis of HLH in adults, although its use in adults has not been formally validated yet. Treatment of HLH is primarily based on the HLH-94 protocol, which involves suppressing the inflammatory response, but the treatment needs to be modified in adults depending on the underlying cause and comorbidities.

The cytokine storms of COVID-19, H1N1 influenza, CRS and MAS compared. Can one sized treatment fit all?

An analysis of published data appertaining to the cytokine storms of COVID-19, H1N1 influenza, cytokine release syndrome (CRS), and macrophage activation syndrome (MAS) reveals many common immunological and biochemical abnormalities. These include evidence of a hyperactive coagulation system with elevated D-dimer and ferritin levels, disseminated intravascular coagulopathy (DIC) and microthrombi coupled with an activated and highly permeable vascular endothelium. Common immune abnormalities include progressive hypercytokinemia with elevated levels of TNF-α, interleukin (IL)-6, and IL-1β, proinflammatory chemokines, activated macrophages and increased levels of nuclear factor kappa beta (NFκB). Inflammasome activation and release of damage associated molecular patterns (DAMPs) is common to COVID-19, H1N1, and MAS but does not appear to be a feature of CRS. Elevated levels of IL-18 are detected in patients with COVID-19 and MAS but have not been reported in patients with H1N1 influenza and CRS. Elevated interferon-γ is common to H1N1, MAS, and CRS but levels of this molecule appear to be depressed in patients with COVID-19. CD4+ T, CD8+ and NK lymphocytes are involved in the pathophysiology of CRS, MAS, and possibly H1N1 but are reduced in number and dysfunctional in COVID-19. Additional elements underpinning the pathophysiology of cytokine storms include Inflammasome activity and DAMPs. Treatment with anakinra may theoretically offer an avenue to positively manipulate the range of biochemical and immune abnormalities reported in COVID-19 and thought to underpin the pathophysiology of cytokine storms beyond those manipulated via the use of, canakinumab, Jak inhibitors or tocilizumab. Thus, despite the relative success of tocilizumab in reducing mortality in COVID-19 patients already on dexamethasone and promising results with Baricitinib, the combination of anakinra in combination with dexamethasone offers the theoretical prospect of further improvements in patient survival. However, there is currently an absence of trial of evidence in favour or contravening this proposition. Accordingly, a large well powered blinded prospective randomised controlled trial (RCT) to test this hypothesis is recommended.

Macrophage activation syndrome: A diagnostic challenge (Review)

Macrophage activation syndrome (MAS) represents an acute and severe inflammatory syndrome, idiopathic (primary) or secondary to infections, rheumatic diseases, malignancies, or drugs. MAS is underdiagnosed, being confused with sepsis, adverse effects of anti-arthritic drugs or exacerbated symptoms of evolving rheumatologic or infectious diseases. Because of the late diagnosis, most patients do not benefit from effective therapy, leading to death. Elucidation of valid early diagnostic criteria of MAS would be a particularly important step in reducing the mortality due to this pathology. Thus, the purpose of this review based on 40 studies centered on the diagnostic criteria of MAS. We detailed the main diagnostic criteria and the few diagnostic scores or sets of criteria that have been recently published. The criteria most frequently encountered in the literature include: Fever, hepatosplenomegaly, hyperferritinemia, hepatopathy, coagulopathy, thrombocytopenia, hypertriglyceridemia, decrease in erythrocyte sedimentation rate and bone marrow hemophagocytosis. The most elaborate diagnostic score will result following an ongoing international project and consensus, the Delphi International Survey.

Clinical and laboratory signs of haemophagocytic lymphohistiocytosis associated with pandemic influenza A (H1N1) infection in patients needing extracorporeal membrane oxygenation: A retrospective observational study

BACKGROUND

Severe pandemic influenza has been associated with the hyperinflammatory condition secondary haemophagocytic lymphohistiocytosis (HLH).

OBJECTIVES

To determine the frequency, degree, character and possible cause of influenza-associated HLH in critically ill patients with severe acute respiratory distress syndrome due to influenza A (H1N1) infection requiring extracorporeal membrane oxygenation (ECMO) support at our hospital.

DESIGN

A retrospective observational study.

PATIENTS AND SETTING

Medical data were retrieved retrospectively from 11 consenting patients of thirteen adults infected with pandemic influenza A (H1N1) 2009 requiring ECMO between July 2009 and January 2010 at the ECMO Centre of Karolinska University Hospital, Stockholm, Sweden. All patients were evaluated for HLH using HLH-2004 criteria and HScore.

RESULTS

Eleven patients (median age 31 years) were included in the study and all survived. All patients showed signs of multiple organ dysfunction and pronounced inflammation, more severe in the four patients with HLH who had significantly higher peak serum concentrations of ferritin (P = 0.024), alkaline phosphatase (P = 0.012) and gamma-glutamyl transferase (P = 0.024), lower concentration of albumin (P = 0.0086) and more frequently hepatomegaly (P = 0.048). Abnormal lymphocyte cytotoxicity (lytic units <10) and a low proportion of natural killer (NK) cells were observed in three of four patients with HLH. Notably, we found a significant inverse correlation between serum ferritin concentration and NK cell and cytotoxic T lymphocyte percentages (rs = -0.74, P = 0.0013 and rs = -0.79, P = 0.0025, respectively). One HLH patient received HLH-directed cytotoxic therapy, another intravenous immunoglobulin and the other two no specific HLH-directed therapy.

CONCLUSION

Critically ill patients, including healthy young adults, with pandemic influenza may develop HLH and should be monitored for signs of hyperinflammation and increasing organ dysfunction, and evaluated promptly for HLH because HLH-directed therapy may then be beneficial. The association of low NK percentages with hyperferritinaemia may suggest a role for reduced NK cell numbers, possibly also cytotoxic T lymphocytes, and subsequently reduced lymphocyte cytotoxicity, in the pathogenesis of hyperinflammation and secondary HLH.

Serum biomarkers for prediction of mortality in patients with COVID-19

BACKGROUND

There is limited information regarding the role of biomarker levels at predicting mortality in patients with the coronavirus disease (COVID-19) pandemic. The purpose of this study is to determine the differences in serum biomarker levels in adults with COVID-19 who survived hospitalization from those who did not.

METHODS

A comprehensive search was completed on PubMed, EMBASE and Cochrane libraries to identify studies of interest. Endpoints of interest were blood counts, hepatic function test, acute phase reactants, cytokines and cardiac biomarkers.

RESULTS

A total of 10 studies with 1584 patients were included in the pooled analyses. Biomarkers that were noted to be significantly higher in those who died from coronavirus disease included: white blood cell count, neutrophil count, C-reactive protein, high sensitivity C-reactive protein, procalcitonin, ferritin, D-dimer, interleukin-6, lactate dehydrogenase, creatine kinase, prothrombin time, aspartate aminotransferase, alanine aminotransferase, total bilirubin and creatinine. Lymphocyte count, platelet count and albumin were significantly lower in patients who died.

CONCLUSION

This pooled analysis of 10 studies including 1584 patients identified significant differences in biomarkers on admission in patients who survived from those who did not. Further research is needed to develop risk stratification models to help with judicious use of limited health-care resources.

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.

Evaluation of natural killer cell assay performance on shipped blood specimens

Documenting the importance of NK cell function as a biomarker for diseases and physiologic conditions including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), will require assays amenable to clinical implementation and standardization. Research studies typically perform NK functional assays on the day of sample collection. This pilot study was conducted to compare assay formats and specimen processing to identify those that are most tolerant of conditions required for shipping and amenable to standardization as shown by inter-assay and inter-laboratory correlation of results. We compared performance within and between assays that measure NK cell function using direct cytotoxicity [chromium-51 release (CRCA) or fluorescence (Flow Cytometry Cytotoxicity Assay, FCCA)] or an indirect surrogate marker (CD107a surface expression)]. Additional variables for within/between assay comparisons included time of testing (same day as specimen collection or next day within 24 h), specimen types [whole blood or isolated peripheral blood mononuclear cells (PBMCs)], and processing method (fresh or cryopreserved). Statistical measures included number of samples tested in assay conditions (n), medians (x͂), interquartile range (IQR), Pearson correlation coefficient (R²), and correlation p-value (p). Samples came from 3 clinics and included 31 participants. Same day testing was only available for the subset of participants enrolled from the site of the laboratory performing CRCA. Results from same day CRCA testing of whole blood were considered the gold standard [n = 10, x͂=10.0%, IQR = 7.2%], and correlated well with PBMCs isolated next day [n = 26, x͂= 15.6%, IQR = 13.1%] [R² = 0.59, p = 0.03]. Next day CRCA results were compromised using whole blood or frozen PBMCs. Next day FCCA cytotoxicity in PBMC [n = 30, x͂=34.1%, IQR = 15.5%] correlated with same day CRCA PMBC [R² = 0.8, p = 0.001] and next day CRCA PMBC [R² = 0.5, p < 0.0001]. CD107a expression after induction by PMA and ionomycin did not correlate with other cytotoxicity measures. NK function can be measured in PBMCs isolated after overnight shipping/storage at ambient temperature and CRCA and FCCA results on this sample type are well correlated.

Interleukin-18 and cytotoxic impairment are independent and synergistic causes of murine virus-induced hyperinflammation

Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening hyperinflammatory syndromes typically associated with underlying hematologic and rheumatic diseases, respectively. Familial HLH is associated with genetic cytotoxic impairment and thereby to excessive antigen presentation. Extreme elevation of serum interleukin-18 (IL-18) has been observed specifically in patients with MAS, making it a promising therapeutic target, but how IL-18 promotes hyperinflammation remains unknown. In an adjuvant-induced MAS model, excess IL-18 promoted immunopathology, whereas perforin deficiency had no effect. To determine the effects of excess IL-18 on virus-induced immunopathology, we infected Il18-transgenic (Il18tg) mice with lymphocytic choriomeningitis virus (LCMV; strain Armstrong). LCMV infection is self-limited in wild-type mice, but Prf1-/- mice develop prolonged viremia and fatal HLH. LCMV-infected Il18-transgenic (Il18tg) mice developed cachexia and hyperinflammation comparable to Prf1-/- mice, albeit with minimal mortality. Like Prf1-/- mice, immunopathology was largely rescued by CD8 depletion or interferon-γ (IFNg) blockade. Unlike Prf1-/- mice, they showed normal target cell killing and normal clearance of viral RNA and antigens. Rather than impairing cytotoxicity, excess IL-18 acted on T lymphocytes to amplify their inflammatory responses. Surprisingly, combined perforin deficiency and transgenic IL-18 production caused spontaneous hyperinflammation specifically characterized by CD8 T-cell expansion and improved by IFNg blockade. Even Il18tg;Prf1-haplosufficient mice demonstrated hyperinflammatory features. Thus, excess IL-18 promotes hyperinflammation via an autoinflammatory mechanism distinct from, and synergistic with, cytotoxic impairment. These data establish IL-18 as a potent, independent, and modifiable driver of life-threatening innate and adaptive hyperinflammation and support the rationale for an IL-18-driven subclass of hyperinflammation.

Do COVID-19 Infections Result in a Different Form of Secondary Hemophagocytic Lymphohistiocytosis

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in significant morbidity and mortality across the world, with no current effective treatments available. Recent studies suggest the possibility of a cytokine storm associated with severe COVID-19, similar to the biochemical profile seen in hemophagocytic lymphohistiocytosis (HLH), raising the question of possible benefits that could be derived from targeted immunosuppression in severe COVID-19 patients. We reviewed the literature regarding the diagnosis and features of HLH, particularly secondary HLH, and aimed to identify gaps in the literature to truly clarify the existence of a COVID-19 associated HLH. Diagnostic criteria such as HScore or HLH-2004 may have suboptimal performance in identifying COVID-19 HLH-like presentations, and criteria such as soluble CD163, NK cell activity, or other novel biomarkers may be more useful in identifying this entity.

Efficacy of Moderately Dosed Etoposide in Macrophage Activation Syndrome–Hemophagocytic Lymphohistiocytosis

Objective

Macrophage activation syndrome (MAS) constitutes 1 subtype of the hyperinflammatory syndrome hemophagocytic lymphohistiocytosis (HLH), and the term MAS-HLH was recently proposed for HLH with underlying autoimmune/autoinflammatory conditions. The mortality of MAS-HLH has been estimated at 5–10%. Here we report our experiences with moderately dosed etoposide in severe MAS-HLH; the objective was to effectively reduce severe hyperinflammatory activity with limited side effects.

Methods

In addition to conventional antiinflammatory treatment, moderately dosed etoposide was administered to 7 children affected by rapidly progressing MAS-HLH with central nervous system (n = 5) and/ or pulmonary (n = 5) involvement. Three had underlying systemic juvenile idiopathic arthritis (sJIA), 2 had atypical sJIA (no arthritis at diagnosis), and 2 had systemic lupus erythematosus. We performed lymphocyte cytotoxicity analyses in all 7 and genetic analyses in 6.

Results

All children promptly responded to moderately dosed etoposide (50–100 mg/m2 once weekly), added to conventional MAS-HLH treatment that was considered insufficient. The mean accumulated etoposide dose was 671 mg/m2 (range 300–1050 mg/m2) as compared to 1500 mg/m2 recommended in the first 8 weeks of the HLH-94/HLH-2004 protocols. One child developed neutropenic fever and another neutropenic sepsis (neutrophils 0.3 × 109/L at therapy onset). Five of 7 children had low percentages (< 5%) of circulating natural killer (NK) cells prior to or in association with diagnosis; NK cell activity was pathologically low in 2 of 5 children studied. Disease-causing variants in HLH-associated genes were not found. All children were alive at latest follow-up (2–9 yrs after onset); neurological symptoms had normalized in 4 of 5 affected children.

Conclusion

Moderately dosed etoposide may be beneficial in severe and/or refractory MAS-HLH.

Understanding of cytokines and targeted therapy in macrophage activation syndrome

Macrophage activation syndrome (MAS) is a potentially life-threatening complication of systemic autoinflammatory/autoimmune diseases, generally systemic juvenile idiopathic arthritis and adult-onset Still's disease. It is characterized by an excessive proliferation of macrophages and T lymphocytes. Recent research revealed that cytokine storm with elevated pro-inflammatory cytokines, including IFN-γ, IL-18, and IL-6, may be central to the pathogenesis of MAS. Though the mainstream of MAS treatment remains corticosteroids and cyclosporine, targeted therapies with anti-cytokine biologics are reported to be promising for controlling systemic inflammation in MAS.

Current treatment options and safety considerations when treating adult-onset Still's disease

INTRODUCTION

Adult onset Still disease (AOSD) is a rare systemic inflammatory condition. The clinical spectrum of this disease ranges from self-limiting forms with mild symptoms to life-threatening cases. Glucocorticoids and non-steroidal anti-inflammatory drugs (NSAIDs) represent the first line of therapy for AOSD, with add-on therapy with second-line drug reserved to steroid-dependent patients and in life-threatening cases. Currently, early treatment with conventional disease modifying anti-rheumatic drugs (DMARDs) and biologic agents blocking causal cytokines is advocated in patients with severe and recalcitrant clinical manifestations.

AREAS COVERED

This review analyzes the available controlled evidence and observational data regarding the efficacy and safety of conventional and biological pharmacological agents in the treatment of AOSD.

EXPERT OPINION

Non-steroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids are effective in controlling clinical manifestations in the majority of AOSD patients. Conventional DMARDs can be 20 effective in some severe and steroid-dependent cases of AOSD; however, anti-cytokine agents represent an effective and overall more suitable alternative in this specific subset of patients. IL-1 and IL-6 blockade are effective in treating systemic and articular inflammation of AOSD patients. IL-1 blockade also has an excellent safety profile and therefore represent the first choice of biologic treatment in this clinical scenario.

A Flow Cytometry-Based Whole Blood Natural Killer Cell Cytotoxicity Assay Using Overnight Cytokine Activation

Background: Measurement of natural killer (NK) cell function has important clinical utility in several diseases. Although the flow cytometry (FC)-based 4-h NK cytotoxicity assay using peripheral blood mononuclear cells (PBMCs) in the clinical laboratory has been used for this purpose, this assay requires large amounts of blood and a rapid PBMC isolation step. Here, we developed an FC-based overnight NK cytotoxicity assay using whole blood (WB), and applied it to patients with liver diseases.

Methods: Peripheral blood of healthy volunteers (n = 28) and patients with liver diseases, including hepatocellular carcinoma (n = 19) and liver cirrhosis (n = 7), was analyzed for complete blood count, absolute NK cell count, and NK cell activity (NKA). NKA was evaluated in three assay types: an FC-based overnight WB NK cytotoxicity assay using carboxyfluorescein diacetate succinimidyl ester-labeled K562 cells in the presence of various cytokine combinations [including interleukin (IL)-2, IL-18, and IL-21], an FC-based 4-h PBMC NK cytotoxicity assay, and an FC-based CD107a degranulation assay using WB and PBMCs.

Results: Optimal cytokine combinations for NK cell activation in WB were determined (IL-2/IL-18, IL-2/IL-21, and IL-2/IL-18/IL-21). A good correlation was observed between WB and PBMC NK cytotoxicity assays; absolute NK cell counts were better correlated with the WB NK cytotoxicity assay than with the PBMC NK cytotoxicity assay. This WB NK cytotoxicity assay showed that patients with liver diseases had significantly lower NK cytotoxicity than healthy volunteers, under stimulation with various cytokines (p < 0.001).

Conclusion: The proposed FC-based overnight WB NK cytotoxicity assay correlates well with the conventional 4-h PBMC NK cytotoxicity assay, demonstrating future potential as a supportive assay for clinical laboratory research and observational studies.

Macrophage activation syndrome in pediatrics: 10 years data from an Indian center

AIMS

Macrophage activation syndrome (MAS) is a dreaded complication of systemic inflammatory diseases and is most commonly seen in systemic juvenile idiopathic arthritis (sJIA). We evaluate the clinical features, laboratory findings and outcomes in pediatric MAS, assess the response to different pharmacological therapies, and finally identify possible factors associated with an unfavorable outcome.

METHODS

This is a retrospective analysis of data from patients diagnosed as having MAS, admitted between July 2008 and April 2018 into the Department of Pediatric Rheumatology, Institute Of Child Health Kolkata. The data noted were the clinical and laboratory features, treatment details, responses to therapy and outcomes.

RESULTS

Thirty-one patients were diagnosed as having MAS. Primary illness was sJIA in 26 (84%), systemic lupus erythematosus in 4 (13%) and Kawasaki disease (KD) in 1 (3%). All had fever with varying degrees of multisystemic involvement. Hyperferritinemia was universally present. Pulse methylprednisolone with cyclosporine was used for treating the majority. Ten patients (32%) expired.

CONCLUSION

Macrophage activation syndrome is a near fatal complication with protean manifestations and multiorgan dysfunction. Hyperferritinemia is characteristic, higher values being associated with increased mortality. Cases resistant to steroids and cyclosporine had a poor prognosis. Late presentations with multiorgan dysfunction were associated with the poorest outcomes.

How autoinflammation may turn into autoimmune inflammation: Insights from monogenetic and complex IL-1 mediated auto-inflammatory diseases

IL-1 mediated auto-inflammatory diseases are characterised by episodes of unexplained fever, generalized and localized inflammation. The characteristic symptoms predominantly result from exaggerated activation of innate immune pathways. However, in some patients with typical IL-1 mediated diseases, chronic disease manifestations develop in the absence of acute inflammation, suggesting the involvement of adaptive immune pathways. We discuss clinical observations as well as novel insights in how chronic activation of innate immune pathways can lead to auto-immune disease features in patients with auto-inflammatory diseases and how we need to better understand these sequelae in order to improve treatment strategies.

Immunopathology of SARS-CoV-2 Infection: Immune Cells and Mediators, Prognostic Factors, and Immune-Therapeutic Implications

The present is a comprehensive review of the immunopathology of Covid-19. The immune reaction to SARS-CoV-2 infection is characterized by differentiation and proliferation of a variety of immune cells with immune mediator production and release, and activation of other pathogen resistance mechanisms. We fully address the humoral and cellular immune changes induced by the virus, with particular emphasis on the role of the “cytokine storm” in the evolution of the disease. Moreover, we also propose some immune alterations (i.e., inflammatory parameters, cytokines, leukocytes and lymphocyte subpopulations) as prognostic markers of the disease. Furthermore, we discuss how immune modifying drugs, such as tocilizumab, chloroquine, glucocorticoids and immunoglobulins, and blood purification therapy, can constitute a fundamental moment in the therapy of the infection. Finally, we made a critical analysis of a number of substances, not yet utilized, but potentially useful in SARS-CoV-2 patients, such as IFN lambda, TNF blockers, ulinastatin, siponimod, tacrolimus, mesenchymal stem cells, inhibitors of mononuclear macrophage recruitment, IL-1 family antagonists, JAK-2 or STAT-3 inhibitors.

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.

Continuous Intravenous Anakinra Infusion to Calm the Cytokine Storm in Macrophage Activation Syndrome

OBJECTIVE

The objective of this study was to report the benefit of a therapeutic approach consisting of intravenous (IV) continuous anakinra (recombinant human interleukin-1 receptor antagonist) infusions in treating severely ill adult patients with secondary hemophagocytic lymphohistiocytosis or macrophage activation syndrome (MAS).

METHODS

A retrospective chart review of five patients treated at Regions Hospital from 2016 to 2019 was conducted. Demographic, clinical, and laboratory characteristics and outcomes were recorded.

RESULTS

Continuous IV anakinra infusions up to 2400 mg/d resulted in rapid serologic, then clinical response in 4 of 5 severely ill patients who were refractory to all other therapies, including subcutaneous anakinra. Subsequently, 3 of 5 patients have been maintained on anakinra or canakinumab, with no recurrence of MAS.

CONCLUSION

Continuous infusion of IV anakinra may result in rapid serologic and subsequent clinical improvement in adult patients with MAS. This method for treating cytokine storm should be considered in the current COVID-19 pandemic in the subgroup of patients with severe disease who have a cytokine storm presentation.

The genetics of macrophage activation syndrome

Macrophage activation syndrome (MAS), or secondary hemophagocytic lymphohistiocytosis (HLH), is a cytokine storm syndrome associated with multi-organ system dysfunction and high mortality rates. Laboratory and clinical features resemble primary HLH, which arises in infancy (1 in 50,000 live births) from homozygous mutations in various genes critical to the perforin-mediated cytolytic pathway employed by NK cells and cytotoxic CD8 T lymphocytes. MAS/secondary HLH is about ten times more common and typically presents beyond infancy extending into adulthood. The genetics of MAS are far less defined than for familial HLH. However, the distinction between familial HLH and MAS/secondary HLH is blurred by the finding of heterozygous perforin-pathway mutations in MAS patients, which may function as hypomorphic or partial dominant-negative alleles and contribute to disease pathogenesis. In addition, mutations in a variety of other pathogenic pathways have been noted in patients with MAS/secondary HLH. Many of these genetically disrupted pathways result in a similar cytokine storm syndrome, and can be broadly categorized as impaired viral control (e.g., SH2P1A), dysregulated inflammasome activity (e.g., NLRC4), other immune defects (e.g., IKBKG), and dysregulated metabolism (e.g., LIPA). Collectively these genetic lesions likely combine with states of chronic inflammation, as seen in various rheumatic diseases (e.g., still disease), with or without identified infections, to result in MAS pathology as explained by the threshold model of disease. This emerging paradigm may ultimately support genetic risk stratification for high-risk chronic and even acute inflammatory disorders. Moving forward, continued whole-exome and -genome sequencing will likely identify novel MAS gene associations, as well as noncoding mutations altering levels of gene expression.

Identification of herbal categories active in pain disorder subtypes by machine learning help reveal novel molecular mechanisms of algesia

Chronic pain is highly prevalent and poorly controlled, of which the accurate underlying mechanisms need be further elucidated. Herbal drugs have been widely used for controlling various pain disorders. The systematic integration of pain herbal data resources might be promising to help investigate the molecular mechanisms of pain phenotypes. Here, we integrated large-scale bibliographic literatures and well-established data sources to obtain high-quality pain relevant herbal data (i.e. 426 pain related herbs with their targets). We used machine learning method to identify three distinct herb categories with their specific indications of symptoms, targets and enriched pathways, which were characterized by the efficacy of treatment to the chronic cough related neuropathic pain, the reproduction and autoimmune related pain, and the cancer pain, respectively. We further detected the novel pathophysiological mechanisms of the pain subtypes by network medicine approach to evaluate the interactions between herb targets and the pain disease modules. This work increased the understanding of the underlying molecular mechanisms of pain subtypes that herbal drugs are participating and with the ultimate aim of developing novel personalized drugs for pain disorders.

NK Cells Regulate CD8+ T Cell Mediated Autoimmunity

Elucidating key factors that regulate immune-mediated pathology in vivo is critical for developing improved strategies to treat autoimmune disease and cancer. NK cells can exhibit regulatory functions against CD8⁺ T cells following viral infection. Here we show that while low doses of lymphocytic choriomeningitis virus (LCMV-WE) can readily induce strong CD8⁺ T cell responses and diabetes in mice expressing the LCMV glycoprotein on β-islet cells (RIP-GP mice), hyperglycemia does not occur after infection with higher doses of LCMV. High-dose LCMV infection induced an impaired CD8⁺ T cell response, which coincided with increased NK cell activity during early time points following infection. Notably, we observed increased NKp46 expression on NK cells during infection with higher doses, which resulted in an NK cell dependent suppression of T cells. Accordingly, depletion with antibodies specific for NK1.1 as well as NKp46 deficiency (Ncr1^gfp/gfp mice) could restore CD8⁺ T cell immunity and permitted the induction of diabetes even following infection of RIP-GP mice with high-dose LCMV. Therefore, we identify conditions where innate lymphoid cells can play a regulatory role and interfere with CD8⁺ T cell mediated tissue specific pathology using an NKp46 dependent mechanism.

Macrophage Activation Syndrome and Secondary Hemophagocytic Lymphohistiocytosis in Childhood Inflammatory Disorders: Diagnosis and Management

Macrophage activation syndrome (MAS), a form of secondary hemophagocytic lymphohistiocytosis, is a frequently fatal complication of a variety of pediatric inflammatory disorders. MAS has been most commonly associated with systemic juvenile idiopathic arthritis (sJIA), as approximately 10% of children with sJIA develop fulminant MAS, with another 30-40% exhibiting a more subclinical form of the disease. Children with other rheumatologic conditions such as systemic lupus erythematosus and Kawasaki disease are also at risk for MAS. Moreover, MAS also complicates various genetic autoinflammatory disorders such as gain of function mutations in the cytosolic inflammasome NLRC4, pediatric hematologic malignancies (e.g., T-cell lymphoma), and primary immunodeficiencies characterized by immune dysregulation. Disease-specific and broadly inclusive diagnostic criteria have been developed to facilitate the diagnosis of MAS. Recently, simple screening tools such as the serum ferritin to erythrocyte sedimentation rate ratio have been proposed. Early diagnosis and rapid initiation of immunosuppression are essential for the effective management of MAS. With a better understanding of the pathophysiology of MAS and the advent of novel therapeutics, a broad immunosuppressive approach to treatment is giving way to targeted anti-cytokine therapies. These treatments include agents that block interleukin-1 (IL-1), IL-6, IL-18, interferon-γ, as well as inhibitors of downstream targets of cytokine signaling (e.g., Janus kinases). Increased early recognition of MAS among pediatric inflammatory disorders combined with the use of effective and less toxic cytokine-targeted therapies should lower the mortality of this frequently fatal disorder.

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.

Genetic architecture study of rheumatoid arthritis and juvenile idiopathic arthritis

BACKGROUND

Rheumatoid arthritis and juvenile idiopathic arthritis are two types of autoimmune diseases with inflammation at the joints, occurring to adults and children respectively. There are phenotypic overlaps between these two types of diseases, despite the age difference in patient groups.

METHODS

To systematically compare the genetic architecture of them, we conducted analyses at gene and pathway levels and constructed protein-protein-interaction network based on summary statistics of genome-wide association studies of these two diseases. We examined their difference and similarity at each level.

RESULTS

We observed extensive overlap in significant SNPs and genes at the human leukocyte antigen region. In addition, several SNPs in other regions of the human genome were also significantly associated with both diseases. We found significantly associated genes enriched in 32 pathways shared by both diseases. Excluding genes in the human leukocyte antigen region, significant enrichment is present for pathways like interleukin-27 pathway and NO2-dependent interleukin-12 pathway in natural killer cells.

DISCUSSION

The identification of commonly associated genes and pathways may help in finding population at risk for both diseases, as well as shed light on repositioning and designing drugs for both diseases.

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.

Convergent pathways of the hyperferritinemic syndromes

Hyperferritinemia and pronounced hemophagocytosis help distinguish a subset of patients with a particularly inflammatory and deadly systemic inflammatory response syndrome. Two clinically similar disorders typify these hyperferritinemic syndromes: hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS). HLH is canonically associated with a complete disturbance of perforin/granzyme-mediated cytotoxicity, whereas MAS occurs in the context of the related rheumatic diseases systemic juvenile idiopathic arthritis and adult-onset Still's disease, with associated IL-1 family cytokine activation. In practice, however, there are accumulating lines of evidence for innate immune dysregulation in HLH as well as partial impairments of cytotoxicity in MAS, and these mechanisms likely represent only a fraction of the host and environmental factors driving hyperferritinemic inflammation. Herein, we present new findings that highlight the pathogenic differences between HLH and MAS, two conditions that present with life-threatening hyperinflammation, hyperferritinemia and hemophagocytosis.

Flip-flops of natural killer cells in autoimmune diseases versus cancers: Immunologic axis

Natural killer (NK) cells play an essential role in the immune response to infections, inflammations, and malignancies. Recent studies suggest that NK cell surface receptors and cytokines are the key points of the disease development and protection. We hypothesized that the interactions between NK cell receptors and targeted cells construct an eventual niche, and this niche has an eventual profile in various autoimmune diseases and cancers. The NK cells preactivated with cytokines, such as interleukin-2 (IL-2), IL-12, IL-15, and IL-18 can have higher cytotoxicity; however, the toxic side effect of IL-2 should be considered. The vicissitudes of NK cell profile and its receptors obey the environmental communications and cell interactions. Our vision around the NK cells as an immune axis remained dual, and we still cannot judge the immune responses based on the NK cell flip-flop. A design of eventual niche to monitor the NK cell and targeted cell interaction is needed to strengthen our ability in diagnosis and treatment approaches based on the NK cells. Here, we have reviewed the shifts in the NK cells and their surface receptors in autoimmune diseases, solid tumors, and leukemia, and also discussed the effective chemokines that affect NK cell activation and proliferation. The main aim of this review is to present a broader vision of the NK cell changes in autoimmune disease and cancers.

Calm in the midst of cytokine storm: a collaborative approach to the diagnosis and treatment of hemophagocytic lymphohistiocytosis and macrophage activation syndrome

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) were historically thought to be distinct entities, often managed in isolation. In fact, these conditions are closely related. A collaborative approach, which incorporates expertise from subspecialties that previously treated HLH/MAS independently, is needed. We leveraged quality improvement (QI) techniques in the form of an Evidence-Based Guideline (EBG) to build consensus across disciplines on the diagnosis and treatment of HLH/MAS.

METHODS

A multidisciplinary work group was convened that met monthly to develop the HLH/MAS EBG. Literature review and expert opinion were used to develop a management strategy for HLH/MAS. The EBG was implemented, and quality metrics were selected to monitor outcomes.

RESULTS

An HLH/MAS clinical team was formed with representatives from subspecialties involved in the care of patients with HLH/MAS. Broad entry criteria for the HLH/MAS EBG were established and included fever and ferritin ≥500 ng/mL. The rheumatology team was identified as the "gate-keeper," charged with overseeing the diagnostic evaluation recommended in the EBG. First-line medications were recommended based on the acuity of illness and risk of concurrent infection. Quality metrics to be tracked prospectively based on time to initiation of treatment and clinical response were selected.

CONCLUSION

HLH/MAS are increasingly considered to be a spectrum of related conditions, and joint management across subspecialties could improve patient outcomes. Our experience in creating a multidisciplinary approach to HLH/MAS management can serve as a model for care at other institutions.