Clinical utility of soluble interleukin-2 receptor in hemophagocytic syndromes: a systematic scoping review

The serum-soluble interleukin-2 receptor (sIL-2r) level is considered an important diagnostic test and disease marker in hemophagocytic syndromes/hemophagocytic lymphohistiocytosis (HPS/HLH). However, this cytokine receptor is rarely measured in clinical practice and has been excluded from recent diagnostic/classification criteria such as the HScore and macrophage activation syndrome (MAS) 16. We performed a systematic scoping review of 64 articles (1975-2016) examining the clinical utility of sIL-2r in HPS/HLH. Twenty-two articles describe sIL-2r as a sensitive diagnostic marker for HLH, but only three distinct datasets actually address sensitivity. The original HLH-2004 Guidelines reported sensitivity of 93% and specificity of 100% for sIL-2r ≥ 2400, based on a pediatric dataset (n = 152) which is published for the first time in this review. Two pediatric studies reported sensitivity of 89% for sIL-2r ≥ 2400 in diagnosis of MAS complicating juvenile idiopathic arthritis (JIA) (n = 27) and 88% for secondary HLH in acute liver failure (n = 9). Twenty articles described sIL-2r as a dynamic marker of disease activity that falls with response to treatment, and 15 described high initial sIL-2r levels >10,000 U/mL as a poor prognostic marker. The ability of sIL-2r to distinguish between subtypes of HPS/HLH was inconsistent. This review confirms the importance of soluble IL-2r as a diagnostic and disease marker in HPS/HLH, but also reveals the need for more primary data about its performance characteristics, particularly in adults. More emphasis should be made in including this simple, inexpensive test in clinical practice and studies of HPS/HLH.

Macrophage activation syndrome in Kawasaki disease: more common than we thought?

OBJECTIVES

To analyze the clinical characteristics, treatment, and outcomes of Kawasaki Disease (KD) patients associated with macrophage activation syndrome (MAS) and to compare two diagnostic standards (the HLH 2009 and Ravelli׳s criteria).

METHODS

All of the studied patients with Kawasaki Disease (KD) were treated at The Children׳s Hospital, Zhejiang University School of Medicine, during 2007-2010. Clinical and laboratory findings were analyzed.

RESULTS

In 719 KD patients, eight patients (1.11%, 81.3 ± 49.4 months, all male) were diagnosed by Ravelli׳s criteria, but only three (0.42%) patients were diagnosed by the HLH 2009 criteria. Aspartate aminotransferase increased significantly in all cases. Alanine aminotransferase, lactate dehydrogenase, and serum ferritin increased significantly in seven cases. Cytopenia and hypertriglyceridemia (>1.5mmol/L) were found in six and five cases, respectively. Hypofibrinogenemia (<1.5g/L) was found in two cases. Three cases showed evidence of hemophagocytosis, but only one case met the HLH 2009 criteria. Ectasia of the coronary arteries occurred in two cases. Seven patients were non-responsive to IVIG. One case died after the combined application of DXM, VP16, and CSA.

CONCLUSIONS

MAS may be a frequently under-recognized complication of KD, because the understanding of complications and diagnostic criteria are still in progress. The HLH 2009 criteria have low sensitivity and specificity for the diagnosis of MAS complicating KD. When hepatosplenomegaly is present in KD patients with abnormal laboratory findings, such as cytopenia, liver dysfunction, hyperferritinemia, elevated serum LDH, hypofibrinogenemia, and hypertriglyceridemia, the presence of MAS should be considered.

A scoping review of the pathophysiology of COVID-19

COVID-19 is a highly heterogeneous and complex medical disorder; indeed, severe COVID-19 is probably amongst the most complex of medical conditions known to medical science. While enormous strides have been made in understanding the molecular pathways involved in patients infected with coronaviruses an overarching and comprehensive understanding of the pathogenesis of COVID-19 is lacking. Such an understanding is essential in the formulation of effective prophylactic and treatment strategies. Based on clinical, proteomic, and genomic studies as well as autopsy data severe COVID-19 disease can be considered to be the connection of three basic pathologic processes, namely a pulmonary macrophage activation syndrome with uncontrolled inflammation, a complement-mediated endothelialitis together with a procoagulant state with a thrombotic microangiopathy. In addition, platelet activation with the release of serotonin and the activation and degranulation of mast cells contributes to the hyper-inflammatory state. Auto-antibodies have been demonstrated in a large number of hospitalized patients which adds to the end-organ damage and pro-thrombotic state. This paper provides a clinical overview of the major pathogenetic mechanism leading to severe COVID-19 disease.

Ferritin and C-reactive protein are predictive biomarkers of mortality and macrophage activation syndrome in adult onset Still's disease. Analysis of the multicentre Gruppo Italiano di Ricerca in Reumatologia Clinica e Sperimentale (GIRRCS) cohort

Objective

To assess the predictive role of ferritin and C-reactive protein (CRP) on occurrence of macrophage activation syndrome (MAS) and mortality in patients with adult onset Still’s disease (AOSD), a rare and severe disease, included in the multicentre Gruppo Italiano di Ricerca in Reumatologia Clinica e Sperimentale (GIRRCS) cohort.

Methods

The predictive role, at the time of diagnosis, of serum levels of ferritin and CRP on occurrence of MAS and mortality, was evaluated by logistic regression analyses and receiver-operating characteristic (ROC) curves were built to identify patients at high risk of MAS and mortality, respectively.

Results

In assessed 147 patients with AOSD, levels of ferritin were predictive of MAS (OR: 1.971; P: 0.002; CI 95%: 1.280–3.035). The ROC curve showed that the best cut-off for ferritin was 1225 ng/ml in predicting MAS (sensitivity 88%; specificity 57%). Levels of CRP were predictive of mortality in these patients (OR: 2.155; P: 0.007; CI 95%: 1.228–3.783). The ROC curve showed that the best cut-off for CRP was 68.7 mg/L in predicting mortality (sensitivity 80%; specificity of 65%).

Conclusions

We reported the predictive role of ferritin and CRP on MAS and mortality, respectively, in a large cohort of patients with AOSD, identifying subsets at higher risk of poor prognosis. Considering that the analysis of CRP and ferritin is widely available, these results could be readily transferable into clinical practice, thus improving the management of patients with AOSD.

Cytokine profile of macrophage activation syndrome associated with Kawasaki disease

The present study aimed to assess the kinetics of cytokine release and compare the accuracy of serum biomarkers for the diagnosis of macrophage activation syndrome (MAS) associated with Kawasaki disease (KD). Serum neopterin, interleukin (IL)-18, IL-6 and soluble tumour necrosis factor receptor type I (sTNFR-I) and sTNFR-II levels were determined using enzyme-linked immunosorbent assay in 78 patients with KD, including five with MAS. Results were compared to the clinical features of MAS. Serum neopterin, IL-18, sTNFR-II levels and sTNFR-II/I ratio were significantly elevated in KD patients with MAS compared to those in the acute phase. Receiver operating characteristic curve analysis revealed areas under the curve and cutoff values of neopterin, IL-18, sTNFR-II levels and sTNFR-II/I ratio were 0.9750/30.0 nmol/L, 0.9813/1165 ng/mL, 0.9969/16,600 pg/mL and 0.9875/4.475, respectively. Serum sTNFR-II levels correlated positively with disease activity. These findings indicate that overproduction of interferon (IFN)-γ and TNF-α reflected by increased serum levels of neopterin and sTNFR-II are closely associated with the pathogenesis of MAS associated with KD. Serum sTNFR-II levels might be a useful marker to diagnose the transition to MAS.

The neutrophil-to-lymphocyte ratio could be a good diagnostic marker and predictor of relapse in patients with adult-onset Still's disease: A STROBE-compliant retrospective observational analysis

The neutrophil-to-lymphocyte ratio (NLR) is the proportion of absolute neutrophil count to lymphocytes on routine complete blood count (CBC) tests, and has been studied as a simple marker of the systemic inflammatory response. This study was performed to investigate whether the NLR could be used as a tool to diagnose and predict prognosis in cases of adult-onset Still's disease (AOSD).We retrospectively reviewed 164 patients with suspected AOSD. Among 164 patients with suspected AOSD, 37 patients received another diagnosis (such as viral infection) and were compared with the 127 patients who received a diagnosis of AOSD. Laboratory tests including CBCs, ferritin, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and the NLR were evaluated.AOSD patients showed higher neutrophil counts, lower lymphocyte counts, higher NLRs, and higher levels of ferritin, ESR, and CRP than non-AOSD patients (all P < .001). In receiver operating characteristic (ROC) curve analysis of the NLR for diagnosis of AOSD, the area under the curve (AUC) was highest at 0.967 (95% CI = 0.940-0.993) with a cutoff value of 3.08. The cutoff value showed the greatest sensitivity (91.7%), specificity (68.4%), and AUC value (0.967) as a diagnostic tool for AOSD. The NLR and treatment appeared to be significant prognostic factors for relapse, but only age showed a significant relationship with death. Furthermore, the NLR was significantly higher in patients with macrophage activation syndrome than in hemophagocytic lymphohistiocytosis (HLH) patients (P = .007). In ROC analysis, the NLR with a cutoff value of 5.86 showed a sensitivity of 89.4%, specificity of 87.8%, and AUC of 0.794.The NLR can be used as a diagnostic tool and predictor of relapse in AOSD, and for differential diagnosis of HLH.

Cytokine storm in severe COVID-19 pneumonia

In this study, laboratorial parameters of hospitalized novel coronavirus (COVID-19) patients, who were complicated with severe pneumonia, were compared with the findings of cytokine storm developing in macrophage activation syndrome (MAS)/secondary hemophagocytic lymphohistiocytosis (sHLH). Severe pneumonia occurred as a result of cytokine storm in some patients who needed intensive care unit (ICU), and it is aimed to determine the precursive parameters in this situation. Also in this study, the aim is to identify laboratory criteria that predict worsening disease and ICU intensification, as well as the development of cytokine storm. This article comprises a retrospective cohort study of patients admitted to a single institution with COVID-19 pneumonia. This study includes 150 confirmed COVID-19 patients with severe pneumonia. When they were considered as severe pneumonia patients, the clinic and laboratory parameters of this group are compared with H-score criteria. Patients are divided into two subgroups; patients with worsened symptoms who were transferred into tertiary ICU, and patients with stable symptoms followed in the clinic. For the patients with confirmed COVID-19 infection, after they become complicated with severe pneumonia, lymphocytopenia (55.3%), anemia (12.0%), thrombocytopenia (19.3%), hyperferritinemia (72.5%), hyperfibrinogenemia (63.7%) and elevated lactate dehydrogenase (LDH) (90.8%), aspartate aminotransaminase (AST) (31.3%), alanine aminotransaminase (ALT) (20.7%) are detected. There were no significant changes in other parameters. Blood parameters between the pre-ICU period and the ICU period (in which their situation had been worsened and acute respiratory distress syndrome [ARDS] was developed) were also compared. In the latter group lymphocyte levels were found significantly reduced (p = 0.01), and LDH, highly sensitive troponin (hs-troponin), procalcitonin, and triglyceride levels were significantly increased (p < 0.05). In addition, there was no change in hemoglobin, leukocyte, platelet, ferritin, and liver function test levels, including patients who developed ARDS, similar to the cytokine storm developed in MAS/sHLH. COVID-19 pneumonia has similar findings as hyperinflammatory syndromes but does not seem to have typical features as in cytokine storm developed in MAS/sHLH. In the severe patient group who has started to develop ARDS signs, a decrease in lymphocyte level in addition to the elevated LDH, hs-troponin, procalcitonin, and triglyceride levels can be a predictor in progression to ICU admission and could help in the planning of anti-cytokine therapy.

Dynamic Changes, Cut-Off Points, Sensitivity, and Specificity of Laboratory Data to Differentiate Macrophage Activation Syndrome from Active Disease

PURPOSE

To compare the laboratory data and changes in these data between patients with MAS and patients with flare-up of the autoimmune diseases.

METHODS

In a prospective study, the static laboratory data and dynamic changes in the selected data in 17 consecutive patients with MAS and 53 patients with active disease of SJIA, PJIA, Kawasaki disease, and SLE were compared. The ROC curve analysis was used to evaluate cut-off points, sensitivity, and specificity of the static and dynamic laboratory data to differentiate between MAS and active disease.

RESULTS

In the MAS group, the mean CRP3, ALT, AST, total bilirubin, ferritin, LDH, PT, PTT, and INR were significantly higher and the mean WBC2, PMN2, Lymph2, Hgb1, 2, 3, ESR2, serum albumin, and sodium were significantly lower than in control group. Some of the important cut-off points were PLT2 < 209000/microliter, AST > 38.5, ALT > 38, WBC < 8200 × 103/UL, ferritin > 5277 ng/mL.

CONCLUSION

The dynamic changes in some laboratory data, especially PLT, can differentiate between MAS and active disease. The changes in WBC, PMN, and ESR and the levels of the liver enzymes may also be helpful in the early differentiation. Very high levels of ferritin may also help the diagnosis along with other clinical and laboratory signs.

Extensive serum biomarker analysis in patients with macrophage activation syndrome associated with systemic lupus erythematosus

The present study employed an antibody array that simultaneously detects 174 cytokines to identify cytokines involved in the development of macrophage activation syndrome (MAS) associated with systemic lupus erythematosus (SLE) with a view to elucidating potential predictive markers. Eight SLE patients, including four with MAS, were analyzed. Levels of 31 cytokines were significantly elevated in the MAS phase compared with those in the active phase of SLE. Among these cytokines, the MAS/active phase ratios of CXCL9 and soluble tumor necrosis factor receptor II (sTNFR-II) were highest. Elevated serum CXCL9 and sTNFR-II levels during the MAS phase were confirmed by ELISA and were strongly correlated with other inflammatory markers, reflecting the disease activity of MAS associated with SLE. These results highlight the clinical significance of serum CXCL-9 and sTNFR-II levels, and indicate they may be useful biomarkers for the diagnosis of MAS associated with SLE.

Pathogenesis of multi-organic failure in autoimmune diseases

Multi-organic failure in the context of autoimmune diseases is a multi-factorial condition where different pathways concur to produce a global system breakdown. Some of these pathways include the coagulation, fibrinolysis, kinin and complement cascades which in normal conditions work together to provide a comprehensive response to injury. In pathologic conditions these regulatory mechanisms are replaced by positive feed-back loops. The common response pattern is the activation of the immune system via endothelium activation. Furthermore, these different plasma-driven mechanisms may induce standardised endothelial cell responses of which the most relevant are the activation of p38, JNK, NF-kbeta and IRF-3 pathways. In this paper we review the common points between these major pathways and how they become activated, contributing to a global clinical picture. We present two examples of apparently different clinical settings, caused by the same global dysfunction: the Macrophage Activation Syndrome and the iatrogenic "cytokine storm" triggered by the administration of anti-CD28 monoclonal antibody TGN1412 in a phase 1 trial.

Clinical significance of serum cytokine profiles for differentiating between Kawasaki disease and its mimickers

OBJECTIVES

To investigate the clinical significance of serum cytokine profiles for differentiating between Kawasaki disease (KD) and its mimickers.

METHODS

Patients with KD, including complete KD, KD shock syndrome (KDSS), and KD with macrophage activation syndrome (KD-MAS), and its mimickers, including multisystem inflammatory syndrome in children, toxic shock syndrome, and Yersinia pseudotuberculosis infection, were enrolled. Serum levels of interleukin (IL)-6, soluble tumor necrosis factor receptor type II (sTNF-RII), IL-10, IL-18, and chemokine (C-X-C motif) ligand 9 (CXCL9) were measured using enzyme-linked immunosorbent assay and compared them with clinical manifestations.

RESULTS

Serum IL-6, sTNF-RII, and IL-10 levels were significantly elevated in patients with KDSS. Serum IL-18 levels were substantially elevated in patients with KD-MAS. Patients with KD-MAS and KD mimickers had significantly elevated serum CXCL9 levels compared with those with complete KD. Area under the receiver operating characteristic curve analysis showed that serum IL-6 was the most useful for differentiating KDSS from the others, IL-18 and CXCL9 for KD-MAS from complete KD, and CXCL9 for KD mimickers from complete KD and KD-MAS.

CONCLUSION

Serum cytokine profiles may be useful for differentiating between KD and its mimickers.

Macrophage activation syndrome with lung involvement complicating adult-onset Still's disease

Adult-onset Still's disease (AOSD) can progress into macrophage activation syndrome (MAS), which may be fatal. We report on a 19-year-old Han Chinese female, who presented with MAS-related pulmonary parenchymal involvement complicating AOSD, and further associated with disseminated intravascular coagulation and generalized tonic-clonic seizure. She was managed by high-dose corticosteroids and pulse cyclophosphamide therapy with a complete recovery of disease activity.

Eighty-six cases of clinical characteristics and outcomes of systemic lupus erythematosus-associated macrophage activation syndrome: A meta-analysis study

OBJECTIVE

To improve our understanding of systemic lupus erythematosus (SLE)-macrophage activation syndrome (MAS).

METHODS

A systematic review was performed, to retrieve all those papers on patients with SLE-MAS, in individual or aggregated form. The data in each of these medical records were extracted and analyzed to identify the characteristics of SLE-MAS.

RESULTS

A total of 86 SLE-MAS patients were included (25 males and 61 females. The mean (±standard error of the mean) age was 31.21 ± 1.694 years. MAS occurred as the initial presentation of SLE in 47 people (54.65%) and during the course of SLE in 39 (45.35%). A coinfection was reported in 23 (26.74%) patients. The mean Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score was 16.54 ± 0.9462. Overall, 10 patients (11.63%) died. The SLEDAI-2K score was higher in patients with MAS as an initial manifestation of SLE than in those where MAS occurred during the course of SLE. The proportion of patients receiving steroid pulse therapy was lower in patients with coinfections. The deceased group demonstrated lower platelet and ferritin levels. Multiple regression analysis revealed that age and thrombocytopenia were independent factors associated with poor prognosis. In receiver operating characteristic analysis, a platelet count cutoff value of ≤47 × 109/L was a predictor of poor outcome.

CONCLUSIONS

SLE-MAS patients demonstrated high lupus activity, and lupus activity was especially higher in patients with MAS as an initial manifestation. Lupus activity was the predominant trigger of lupus MAS. Thrombocytopenia was an independent factor for poor prognosis.

Macrophage Activation Syndrome Associated With Adult Onset Still's Disease

Macrophage activation syndrome (MAS) is a potentially lethal complication of chronic rheumatological conditions like ankylosing spondylitis, rheumatoid arthritis, and adult-onset Still's disease (AOSD). It is a multisystem inflammatory syndrome caused by immense cytokine release from activated lymphocytes and macrophages. We give an account of the incidence of a twenty years old Asian girl suffering from non-remitting fever and an evanescent rash for last ten weeks. Physical examination and laboratory work-up suggested high grade fever, pancytopenia, hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia and impaired liver function. Bone marrow biopsy was also done. It showed active hemophagocytosis. She was diagnosed as a case of Macrophage Activation Syndrome associated with Adult Onset Still's disease. She was treated with high dose steroids and cyclosporine and recovered completely.

Neutrophil-to-Lymphocyte Ratio and System Score Could Predict the Occurrence of Macrophage Activation Syndrome in Patients with Adult-Onset Still's Disease

OBJECTIVE

To investigate the characteristics of Adult-onset Still's disease (AOSD) patients with macrophage activation syndrome (MAS) and explore the risk factors for the development of MAS.

STUDY DESIGN

A case-control study. Place and Duration of the Study: Department of Rheumatology and Immunology, the Second Hospital of Anhui Medical University, Anhui, China, from January 2008 to June 2024.

METHODOLOGY

AOSD patients with MAS (AOSD-MAS) and without MAS (AOSD-nonMAS) were compared. Clinical features and laboratory results from two groups were analysed using the independent samples t-test or Mann-Whitney U test. Fisher's exact test or Pearson's Chi-square test was used to compare the variables between the two groups. The multivariable logistic regression analysis was applied to identify AOSD with MAS-associated factors. The value of risk factors in predicting MAS occurrence was carried out by a receiver operating characteristic validation analysis.

RESULTS

MAS patients showed higher prevalence of sore throat, splenomegaly and abnormal liver function, a lower prevalence of arthrodynia and higher levels of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio, alanine aminotransferase, aspartate aminotransferase, lactic dehydrogenase, serum ferritin, D-Dimer levels, and a higher AOSD system score, along with a lower lymphocyte count (p <0.05). Multivariate logistic regression analysis identified NLR and AOSD system scores as predictors of MAS. An optimised threshold of 17.455 and 5.500 for NLR and AOSD system score yielded a sensitivity of 84.60% (38.50) and a specificity of 91.00%, (47.40).

CONCLUSION

Early detection of MAS in AOSD may be facilitated by monitoring these factors, particularly NLR and AOSD system scores.

KEY WORDS

Adult-onset still's disease, Macrophage activation syndrome, Risk factor.

Predictive factors and prognosis of macrophage activation syndrome associated with adult-onset Still's disease

OBJECTIVES

To summarise the clinical data of adult-onset Still's disease (AOSD) patients and analyse their clinical manifestations, predictors for the formation and prognosis of macrophage activation syndrome (MAS).

METHODS

A retrospective analysis was performed on the clinical data of 182 AOSD hospitalised patients from the Department of Rheumatology of the First Affiliated Hospital of Zhengzhou University, China from January 2012 to August 2018, including 11 patients with pathogenesis of MAS.

RESULTS

Compared with the patients without MAS, the patients with MAS had a higher incidence of splenomegaly and pericarditis at the initial diagnosis of AOSD. The number of platelets (PLT) and the concentration of fibrinogen (FIB), D-Dimer and ferritin were significantly higher in AOSD-MAS patients. Multivariate regression analysis showed that splenomegaly (OR: 5.748, 95% CI: 1.378-23.984, p=0.016), pericarditis (OR: 6.492, 95% CI: 1.43-29.461, p=0.015), and ferritin >2000 μg/L (OR: 4.715, 95% CI: 1.12-19.86, p=0.035) were risk factors for MAS. Survival analysis indicated that the mortality of AOSD-MAS patients was significantly higher than patients without MAS.

CONCLUSIONS

Splenomegaly, pericarditis and elevated ferritin concentration are risk factors for MAS formation in AOSD patients. MAS resulted in a significant decrease in the survival rate of the AOSD patients.

Clinical and Laboratory Profile of Macrophage Activation Syndrome in Kawasaki Disease: A Single Centre Cross-Sectional Study

OBJECTIVE

To study the prevalence of macrophage activation syndrome (MAS) in children with Kawasaki disease (KD) and to devise a classification tree for predicting MAS in early KD based on easily available clinical and laboratory information using artificial intelligence (AI) technology.

METHODS

A cross-sectional observational study was conducted (March 2020 - October 2021) during which hospitalized children aged 1-18 years with KD were consecutively enrolled. Those with a positive RTPCR test or IgM/IgG serology for COVID-19 were excluded. The clinical and laboratory profiles of children with and without MAS were studied. A multivariable logistic regression (LR) model was developed utilizing backward elimination method to determine the relationship between select candidate predictor variables and MAS in patients with KD. A classification tree was created based on these using artificial intelligence algorithms.

RESULTS

Sixty-two children were diagnosed with KD during the study period, of these, 42 children with KD were included; 14 (33.3 %) were diagnosed with MAS. The median (IQR) duration of fever (days) was significantly more in MAS than those without MAS [7 (5, 15) vs 5 (5, 9), P < 0.05]. Serum albumin (g/dL) was significantly lower in those with MAS [2.3 (2.2, 2.7) vs 2.8 (2.3, 3.1), P = 0.03]. The classification tree constructed using the AI-based algorithm predicted that in children with KD who had myocardial dysfunction, serum albumin < 2.8 g/dL and fever > 6 days duration at admission had an increased likelihood of developing MAS. In children without myocardial dysfunction, alanine transaminase (ALT) levels > 70 U/L and fever > 5 days were equally predictive of MAS.

CONCLUSION

Nearly one-third of the children with KD had MAS. Clinicians should consider screening all children with KD for MAS at admission. A classification tree based on the presence of myocardial dysfunction, duration of fever > 6 days, ALT levels and hypoalbuminemia can identify MAS in the course of KD.

The NLRP3 inflammasome is essential for IL-18 production in a murine model of macrophage activation syndrome

Hyperinflammatory disease is associated with an aberrant immune response resulting in cytokine storm. One such instance of hyperinflammatory disease is known as macrophage activation syndrome (MAS). The pathology of MAS can be characterised by significantly elevated serum levels of interleukin-18 (IL-18) and interferon gamma (IFNγ). Given the role for IL-18 in MAS, we sought to establish the role of inflammasomes in the disease process. Using a murine model of CpG-oligonucleotide-induced MAS, we discovered that the expression of the NLRP3 inflammasome was increased and correlated with IL-18 production. Inhibition of the NLRP3 inflammasome or the downstream caspase-1 prevented MAS-mediated upregulation of IL-18 in the plasma but, interestingly, did not alleviate key features of hyperinflammatory disease including hyperferritinaemia and splenomegaly. Furthermore blockade of IL-1 receptor with its antagonist IL-1Ra did not prevent the development of CpG-induced MAS, despite being clinically effective in the treatment of MAS. These data demonstrate that, during the development of MAS, the NLRP3 inflammasome was essential for the elevation in plasma IL-18 - a key cytokine in clinical cases of MAS - but was not a driving factor in the pathogenesis of CpG-induced MAS.

Emapalumab in Patients With Macrophage Activation Syndrome Associated With Still's Disease: A Population Pharmacokinetic/Pharmacodynamic Analysis

Macrophage activation syndrome (MAS) is a life-threatening form of secondary haemophagocytic lymphohistiocytosis (HLH) associated with rheumatic diseases, most commonly Still's disease. This study aimed to develop a population pharmacokinetic (PK)/pharmacodynamic (PD) model for emapalumab, a fully human monoclonal antibody that targets interferon-gamma (IFNγ), in patients with MAS associated with Still's disease. A two-compartment disposition model based on data from patients with primary HLH administered emapalumab (1 mg/kg every 3 days, with possible increases to 3, 6 or 10 mg/kg) was re-estimated for patients with MAS administered emapalumab (6 mg/kg, then 3 mg/kg every 3 days until day 15 and twice weekly until day 28). An exploratory population PK/PD analysis comprising patients' PD data for total IFNγ, chemokine C-X-C motif ligand 9 (CXCL9) and ferritin was performed. Emapalumab clearance was generally linear and independent of total IFNγ levels in patients with MAS (n = 14). Estimated baseline levels of CXCL9 (a marker of IFNγ activity), soluble interleukin-2 receptor α (sIL-2Rα; a marker of hyperinflammation) and ferritin (a clinical marker of MAS disease activity) were 8400, 6550 and 15,300 μg/L, respectively. All three PD markers responded rapidly to changes in emapalumab concentration. Emapalumab almost completely suppressed CXCL9, sIL2-Rα, and ferritin production (estimated reduction in synthesis rate: 98.3%, 87%, and 99.6%, respectively). Population PK/PD modeling indicated that emapalumab rapidly suppresses markers of hyperinflammation in patients with MAS associated with Still's disease. Emapalumab dosing regimen used in clinical trials in patients with MAS is unlikely to need adjustment.