Defective natural killer cell function in patients with hemophagocytic lymphohistiocytosis and in first degree relatives

Hemophagocytic lymphohistiocytosis and macrophage activation syndrome: two rare sides of the same devastating coin

Hemophagocytic lymphohistiocytosis (HLH) is a rare genetic hyperinflammatory syndrome that occurs early in life. Macrophage activation syndrome (MAS) usually refers to a secondary form of HLH associated with autoimmunity, although there are other causes of secondary HLH, such as infections and malignancy. In this article, we reviewed the concepts, epidemiology, clinical and laboratory features, diagnosis, differential diagnosis, prognosis, and treatment of HLH and MAS. We also reviewed the presence of MAS in the most common autoimmune diseases that affect children. Both are severe diseases that require prompt diagnosis and treatment to avoid morbidity and mortality.

Approaching hemophagocytic lymphohistiocytosis

Hemophagocytic Lymphohistiocytosis (HLH) is a rare clinical condition characterized by sustained but ineffective immune system activation, leading to severe and systemic hyperinflammation. It may occur as a genetic or sporadic condition, often triggered by an infection. The multifaceted pathogenesis results in a wide range of non-specific signs and symptoms, hampering early recognition. Despite a great improvement in terms of survival in the last decades, a considerable proportion of patients with HLH still die from progressive disease. Thus, prompt diagnosis and treatment are crucial for survival. Faced with the complexity and the heterogeneity of syndrome, expert consultation is recommended to correctly interpret clinical, functional and genetic findings and address therapeutic decisions. Cytofluorimetric and genetic analysis should be performed in reference laboratories. Genetic analysis is mandatory to confirm familial hemophagocytic lymphohistiocytosis (FHL) and Next Generation Sequencing is increasingly adopted to extend the spectrum of genetic predisposition to HLH, though its results should be critically discussed with specialists. In this review, we critically revise the reported laboratory tools for the diagnosis of HLH, in order to outline a comprehensive and widely available workup that allows to reduce the time between the clinical suspicion of HLH and its final diagnosis.

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.

Clinical Characteristics and Outcomes of 101 Children with Hemophagocytic Lymphohistiocytosis: A Four-Year Single-Center Experience from Egypt

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition, arising either due to genetic mutations or from a variety of underlying diseases. This prospective observational study reports the clinical and laboratory data as well as the outcome of pediatric HLH in Egypt. HLH was diagnosed according to the Histiocyte Society HLH-2004 diagnostic criteria conducted at Alexandria University Children's Hospital over four years. One-hundred-one patients were enrolled (44 males and 57 females), and the median age at presentation was 13.1 months (range: 1 day - 181.4 months). Almost 75% of the patients had consanguineous parents, and one-third had a history of an affected family member (HLH or HLH-like illness). The median time interval between the first HLH symptom and diagnosis was 34 days. At diagnosis, patients were preliminarily classified as having primary HLH in 61% of patients and secondary HLH in 39% of patients. The diagnosis was confirmed genetically in 57 patients. Seventy-eight percent of patients received the HLH-94 and HLH-2004 protocols, only seven patients have undergone hematopoietic stem cell transplantation. The overall survival was 26.4% by the end of the study; the most common cause of death was uncontrolled disease activity. This descriptive study, on a large cohort of pediatric HLH in Africa and the Middle East, sheds some light on the epidemiological characteristics of HLH patients and the available diagnostic and therapeutic tools. The mortality rate was considerably high, highlighting the importance of early diagnosis and initiation of appropriate therapy.

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.

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.

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.

Macrophage activation syndrome complicating rheumatic diseases in adults: case-based review

Macrophage activation syndrome (MAS) is a life-threatening complication of rheumatologic diseases. Data regarding the clinical course, management and outcome of adults with MAS is limited. Therefore, we aimed to describe the clinical features, treatment and outcome of adult patients with MAS, and review the literature for previous cohorts. We retrospectively reviewed patients with MAS complicating rheumatologic diseases between the years 2007 and 2017. Through Pubmed, Medline and Scopus literature search we identified previous cases of adult patients with MAS. We identified 7 patients with MAS complicating rheumatologic diseases (5 females and 2 males). The median age of diagnosis was 32 (range 26-57) years. The median follow-up was 30 months (range 6.95-36.5) months. The underlying rheumatologic disease was adult onset Still's disease (AOSD) in 3 patients, systemic juvenile idiopathic arthritis (sJIA) in 2 patients, systemic lupus erythematosus (SLE) in 1 patient, and systemic vasculitis in 1 patient. Four patients developed MAS concurrently with the clinical development of the rheumatologic disease. All the patients were treated with systemic corticosteroids. Five patients were treated with cyclosporine A, one of which received combination therapy with anakinra, and one received tocilizumab. Two patients deceased during the hospitalization. We identified 92 patients from literature cohorts, 73 (79%) of them with AOSD. MAS developed concurrently with the underlying rheumatologic disease in 25 (27%) patients, and 30 (33%) patients deceased. Our cohort and previous cohorts demostrate that MAS often presents concurrently with the underlying rheumatologic disease and is associated with a high mortality rate. Further larger prospective studies are needed to determine the optimal management of MAS.

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.

Hemophagocytic Lymphohistiocytosis Associated with Natural T-cell Leukemia

Hemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening syndrome of excessive immune activation. It can be triggered by a variety of events that disrupt immune homeostasis, infection being the most common of them. We report a case of a 36-year-old male diagnosed with HLH associated with natural T-cell leukemia. The purpose of this report is to call attention to the clinical presentation, diagnosis, and treatment of HLH.

Macrophage Activation Syndrome

Hemophagocytic lymphohistiocytosis (HLH), or termed macrophage activation syndrome (MAS) when associated with rheumatic disorders, is a frequently fatal complication of infections, rheumatic disorders, and hematopoietic malignancies. Clinically, HLH/MAS is a life-threatening condition that is usually diagnosed among febrile hospitalized patients (children and adults) who commonly present with unremitting fever and a shock-like multiorgan dysfunction scenario. Laboratory studies reveal pancytopenia, elevated liver enzymes, elevated markers of inflammation (ESR, CRP), hyperferritinemia, and features of coagulopathy. In about 60% of cases, excess hemophagocytosis (macrophages/histiocytes engulfing other hematopoietic cell types) is noted on biopsy specimens from the bone marrow, liver, lymph nodes, and other organs. HLH/MAS has been hypothesized to occur when a threshold level of inflammation has been achieved, and genetic and environmental risk factors are believed to contribute to the hyperinflammatory state. A broad variety of infections, from viruses to fungi to bacteria, have been identified as triggers of HLH/MAS, either in isolation or in addition to an underlying inflammatory disease state. Certain infections, particularly by members of the herpesvirus family, are the most notorious triggers of HLH/MAS. Treatment for infection-triggered MAS requires therapy for both the underlying infection and dampening of the hyperactive immune response.

Macrophage activation syndrome associated with griscelli syndrome type 2: case report and review of literature

Macrophage activation syndrome (MAS) is a severe and potentially fatal life-threatening condition associated with excessive activation and expansion of T cells with macrophages and a high expression of cytokines, resulting in an uncontrolled inflammatory response, with high levels of macrophage colony-stimulating factor and causing multiorgan damage. This syndrome is classified into primary (genetic/familial) or secondary forms to several etiologies, such as infections, neoplasias mainly hemopathies or autoimmune diseases. It is characterised clinically by unremitting high fever, pancytopaenia, hepatosplenomegaly, hepatic dysfunction, encephalopathy, coagulation abnormalities and sharply increased levels of ferritin. The pathognomonic feature of the syndrome is seen on bone marrow examination, which frequently, though not always, reveals numerous morphologically benign macrophages exhibiting haemophagocytic activity. Because MAS can follow a rapidly fatal course, prompt recognition of its clinical and laboratory features and immediate therapeutic intervention are essential. However, it is difficult to distinguish underlying disease flare, infectious complications or medication side effects from MAS. Although, the pathogenesis of MAS is unclear, the hallmark of the syndrome is an uncontrolled activation and proliferation of T lymphocytes and macrophages, leading to massive hypersecretion of pro-inflammatory cytokines. Mutations in cytolytic pathway genes are increasingly being recognised in children who develop MAS in his secondary form. We present here a case of Macrophage activation syndrome associated with Griscelli syndrome type 2 in a 3-years-old boy who had been referred due to severe sepsis with non-remitting high fever, generalized lymphoadenopathy and hepato-splenomegaly. Laboratory data revealed pancytopenia with high concentrations of triglycerides, ferritin and lactic dehydrogenase while the bone marrow revealed numerous morphologically benign macrophages with haemophagocytic activity that comforting the diagnosis of a SAM according to Ravelli and HLH-2004 criteria. Griscelli syndrome (GS) was evoked on; consanguineous family, recurrent infection, very light silvery-gray color of the hair and eyebrows, Light microscopy examination of the hair showed large, irregular clumps of pigments characteristic of GS. The molecular biology showed mutation in RAB27A gene confirming the diagnosis of a Griscelli syndrome type 2. The first-line therapy was based on the parenteral administration of high doses of corticosteroids, associated with immunosuppressive drugs, cyclosporine A and etoposide waiting for bone marrow transplantation (BMT).

Evidence-based diagnosis and treatment of macrophage activation syndrome in systemic juvenile idiopathic arthritis

BACKGROUND

Macrophage activation syndrome (MAS) is a severe and potentially lethal complication of several inflammatory diseases but seems particularly linked to systemic juvenile idiopathic arthritis (sJIA). Standardized diagnostic and treatment guidelines for MAS in sJIA are currently lacking. The aim of this systematic literature review was to evaluate currently available literature on diagnostic criteria for MAS in sJIA and provide an overview of possible biomarkers for diagnosis, disease activity and treatment response and recent advances in treatment.

METHODS

A systematic literature search was performed in MEDLINE, EMBASE and Cochrane. 495 papers were identified. Potentially relevant papers were selected by 3 authors after which full text screening was performed. All selected papers were evaluated by at least two independent experts for validity and level of evidence according to EULAR guidelines.

RESULTS

27 papers were included: 7 on diagnosis, 9 on biomarkers and 11 on treatment. Systematic review of the literature confirmed that there are no validated diagnostic criteria for MAS in sJIA. The preliminary Ravelli criteria, with the addition of ferritin, performed well in a large retrospective case-control study. Recently, an international consortium lead by PRINTO proposed a new set of diagnostic criteria able to distinguish MAS from active sJIA and/or infection with superior performance. Other promising diagnostic biomarkers potentially distinguish MAS complicating sJIA from primary and virus-associated hemophagocytic lymphohistiocytosis. The highest level of evidence for treatment comes from case-series. High dose corticosteroids with or without cyclosporine A were frequently reported as first-line therapy. From the newer treatment modalities, promising responses have been reported with anakinra.

CONCLUSION

MAS in sJIA seems to be diagnosed best by the recently proposed PRINTO criteria, although prospective validation is needed. Novel promising biomarkers for sJIA related MAS are in need of prospective validation as well, and are not widely available yet. Currently, treatment of MAS in sJIA relies more on experience than evidence based medicine. Taking into account the severity of MAS and the scarcity of evidence, early expert consultation is recommended as soon as MAS is suspected.

NK cells regulating T cell responses: mechanisms and outcome

Natural killer (NK) cells are important innate effectors in immunity. NK cells also have a role in the regulation of the adaptive immune response, and have been shown, in different contexts, to stimulate or inhibit T cell responses. Recent findings have expanded our understanding of the mechanisms underlying this regulation, revealing that regulation by NK cells can result from both direct interactions between NK cells and T cells, as well as indirectly, involving interactions with antigen presenting cells and the impact of NK cells on infected cells and pathogen load. We review these recent findings here, and outline emerging principles of how this regulation influences the overall outcome of adaptive immunity in infection and disease.

Macrophage Activation Syndrome

Macrophage activation syndrome (MAS) is a potentially life-threatening complication of rheumatic disorders that occurs most commonly in systemic juvenile idiopathic arthritis. In recent years, there have been several advances in the understanding of the pathophysiology of MAS. Furthermore, new classification criteria have been developed. Although the place of cytokine blockers in the management of MAS is still unclear, interleukin-1 inhibitors represent a promising adjunctive therapy, particularly in refractory cases.

Clinical features and correct diagnosis of macrophage activation syndrome

Macrophage activation syndrome (MAS) is increasingly recognized among febrile hospitalized patients. Clinically, MAS resembles multiorgan dysfunction and shock. Laboratory features include hepatobiliary dysfunction, coagulopathy, pancytopenia, hyperferritinemia and markers of immune activation. Pathologically, hemophagocytosis is commonly seen but is only present in 60% of MAS patients. MAS, or secondary hemophagocytic lymphohistiocytosis (HLH), is triggered by infectious (e.g., herpes family viruses), rheumatologic (e.g., systemic lupus erythematosus [SLE]) and oncologic (e.g., T-cell leukemia) conditions. Formal HLH criteria, while specific, are frequently insensitive for MAS diagnosis. Thus, disease-specific (e.g., SLE) and generic MAS criteria have been published. Recently, novel criteria for MAS in children with systemic juvenile idiopathic arthritis (sJIA) were developed and are a key focus of this review.

Identification of the best cutoff points and clinical signs specific for early recognition of macrophage activation syndrome in active systemic juvenile idiopathic arthritis

OBJECTIVES

The purpose of our study was to detect early clinical and laboratory signs that help to discriminate macrophage activation syndrome (MAS) from active systemic juvenile idiopathic arthritis (SJIA) without MAS.

METHODS

Our retrospective study was based on reviewing the medical charts of the children admitted to the rheumatology department with active SJIA and definite MAS (n = 18) and without MAS (n = 40). We evaluated the data related to SJIA and MAS at the moment of the patient׳s admission. If the patient had signs of MAS since admission or developed definite MAS later during this flare, he was referred to the main group. The children who did not have MAS during the flare episode and did not have MAS in the past medical history were in the control group. We calculated the cutoff points for MAS parameters, performed the analysis of sensitivity and specificity, identified the predictors, and provided the preliminary diagnostic rule through "the-number-of-criteria-present" approach.

RESULTS

The clinical signs were relevant to MAS in SJIA: oligoarticular disease course (OR = 5.6), splenomegaly (OR = 67.6), hemorrhages (OR = 33.0), and respiratory failure (OR = 11.3). The involvement of wrist (OR = 0.2), MCP (OR = 0.1), and PIP joints (OR = 0.1) was protective against MAS development. The best cutoffs for laboratory parameters were PLT ≤ 211 × 10(9)/l, WBC ≤ 9.9 × 10(9)/l, AST > 59.7U/l, LDH > 882U/l, albumin ≤ 2.9g/dl, ferritin > 400μg/l, fibrinogen ≤ 1.8g/l, and proteinuria. The laboratory variables were more precise in the discrimination of early MAS than clinical: any 3 or more laboratory criteria provided the highest specificity (1.0) and sensitivity (1.0) and OR = 2997.

CONCLUSIONS

We detected clinical and laboratory markers and created preliminary diagnostic (laboratory) guidelines for early discrimination of MAS in active SJIA.

High dose Anakinra for treatment of severe neonatal Kawasaki disease: a case report

We report an 11-week-old female who presented with Kawasaki disease (KD) complicated by macrophage activation syndrome (MAS). The infant presented to the hospital with persistent fever, cough, diarrhea, and emesis, among other symptoms. Her condition quickly began to decompensate, and she developed classic features (conjunctivitis, rash, cracked lips, distal extremity edema) prompting a diagnosis of acute KD. The patient was treated with standard therapy for KD including three doses of intravenous immunoglobulin (IVIG), aspirin, and high dose glucocorticoids with no change in her condition. Due to a high suspicion for MAS, high dose anakinra therapy was initiated resulting in dramatic clinical improvements. She also received one dose of infliximab for concern for coronary artery changes, and over the course of several months, anakinra and high dose glucocorticoids were tapered. Nearly complete reversal of echocardiogram changes were observed after 8 months, and the infant is now off all immunosuppressive therapy. In this case report, we briefly review the importance of early recognition of MAS in pediatric patient populations with rheumatic diseases, and we suggest early initiation of anakinra therapy as a rapid and effective treatment option.

Perforin and human diseases

Natural killer (NK) cells and cytotoxic T lymphocytes (CTL) use a highly toxic pore-forming protein perforin (PFN) to destroy cells infected with intracellular pathogens and cells with pre-cancerous transformations. However, mutations of PFN and defects in its expression can cause an abnormal function of the immune system and difficulties in elimination of altered cells. As discussed in this chapter, deficiency of PFN due to the mutations of its gene, PFN1, can be associated with malignancies and severe immune disorders such as familial hemophagocytic lymphohistiocytosis (FHL) and macrophage activation syndrome. On the other hand, overactivity of PFN can turn the immune system against autologous cells resulting in other diseases such as systemic lupus erythematosus, polymyositis, rheumatoid arthritis and cutaneous inflammation. PFN also has a crucial role in the cellular rejection of solid organ allografts and destruction of pancreatic β-cells resulting in type 1 diabetes. These facts highlight the importance of understanding the biochemical characteristics of PFN.

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

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

Immunophenotype predicts outcome in pediatric acute liver failure

OBJECTIVES

We sought to determine whether markers of T-cell immune activation, including soluble interleukin 2 receptor alpha (sIL2Rα) levels predict outcome in pediatric acute liver failure and may target potential candidates for immunomodulatory therapy.

METHODS

We analyzed markers of immune activation in 77 patients with pediatric acute liver failure enrolled in a multinational, multicenter study. The outcomes were survival with native liver, liver transplantation (LT), and death without transplantation within 21 days after enrollment.

RESULTS

Adjusting for multiple comparisons, only normalized serum sIL2Rα level differed significantly among the 3 outcomes, and was significantly higher in patients who died (P=0.02) or underwent LT (P=0.01) compared with those who survived with their native liver. The 37 patients with normal sIL2Rα levels all lived, 30 with their native liver. Of the 15 subjects with markedly high sIL2Rα (≥5000 IU/mL), 5 survived with their native liver, 2 died, and 8 underwent LT.

CONCLUSIONS

Evidence of immune activation is present in some patients who die or undergo LT. Patients with higher sIL2Rα levels were more likely to die or undergo LT within 21 days than those with lower levels. Identifying a subset of patients at risk for poor outcome may form the foundation for targeted clinical trials with immunomodulatory drugs.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

Objective.

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

Methods.

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

Results.

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

Conclusion.

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

Macrophage activation syndrome as part of systemic juvenile idiopathic arthritis: diagnosis, genetics, pathophysiology and treatment

Macrophage activation syndrome (MAS) is a severe, frequently fatal complication of systemic juvenile idiopathic arthritis (sJIA) with features of hemophagocytosis leading to coagulopathy, pancytopenia, and liver and central nervous system dysfunction. MAS is overt in 10% of children with sJIA but occurs subclinically in another 30-40%. It is difficult to distinguish sJIA disease flare from MAS. Development of criteria for establishing MAS as part of sJIA are under way and will hopefully prove sensitive and specific. Mutations in cytolytic pathway genes are increasingly being recognized in children who develop MAS as part of sJIA. Identification of these mutations may someday assist in MAS diagnosis. Defects in cytolytic genes have provided murine models of MAS to study pathophysiology and treatment. Recently, the first mouse model of MAS not requiring infection but rather dependent on repeated stimulation through Toll-like receptors was reported. This provides a model of MAS that may more accurately reflect MAS pathology in the setting of autoinflammation or autoimmunity. This model confirms the importance of a balance between pro- and anti-inflammatory cytokines. There has been remarkable progress in the use of anti-pro-inflammatory cytokine therapy, particularly against interleukin-1, in the treatment of secondary forms of MAS, such as in sJIA.

Approach to Hemophagocytic Syndromes

Hemophagocytic lymphohistiocytosis (HLH) is a potentially fatal hyperinflammatory condition. It may occur as a primary (genetic) condition due to mutations in genes important in the cytolytic secretory pathway that cause perforin and granzymes to induce apoptosis in target cells. Primary HLH is divided into familial HLH (FHLH1-5), in which HLH is the only manifestation of disease, and other genetic causes in which HLH is one of several clinical manifestations. The identical clinical findings may arise secondary to infectious, rheumatologic, malignant, or metabolic conditions. Whether primary or secondary, HLH therapy needs to be instituted promptly to prevent irreversible tissue damage. It is helpful to think of HLH as the severe end of the spectrum of hyperinflammatory disorders when the immune system starts to damage host tissues (immunopathology). Therefore, no single clinical feature alone is diagnostic for HLH, and it is important that the entire clinical presentation be considered in making the diagnosis. This article contains a discussion of the genetic background, clinical presentation, diagnostic dilemmas, and features that are helpful in making the diagnosis of HLH, along with a discussion of common problems in its management.

Familial haemophagocytic lymphohistiocytosis: advances in the genetic basis, diagnosis and management

Familial haemophagocytic lymphohistiocytosis (FHL) is a rare autosomal recessive disorder of immune dysregulation associated with uncontrolled T cell and macrophage activation and hypercytokinaemia. The incidence of FHL is 0·12/100·000 children born per year, with a male to female ratio of 1:1. The disease is classified into six different types based on genetic linkage analysis and chromosomal localization; five specific genetic defects have been identified, which account for approximately 90% of all patients. Type 1 is due to an as yet unidentified gene defect located on chromosome nine. Type 2 is caused by mutations in the perforin (PRF1) gene, type 3 by mutations in the Munc-13-4 (UNC13D) gene, type 4 by mutations in the syntaxin 11 (STX11) gene and the recently described type 5 due to mutations in the gene encoding syntaxin binding protein 2 (STXBP-2). The incidence of the five types varies in different ethnic groups. The most common presenting features are pyrexia of unknown origin, pronounced hepatosplenomegaly and cytopenias. Neurological features tend to present later and are associated with poor prognosis. Absent or decreased lymphocyte cytotoxicity is the cellular hallmark of FHL. Biochemical features such as hyperferritinaemia, hypertriglyceridaemia and hypofibrinogenaemia are usually present, along with high levels of soluble interleukin 2 receptor in the blood and cerebrospinal fluid. Bone marrow aspirate may demonstrate the characteristic haemophagocytes, but initially is non-diagnostic in two-thirds of patients. Established international clinical, haematological and biochemical criteria now facilitate accurate clinical diagnosis. The disease is fatal unless a haematopoietic stem cell transplant (HSCT) is performed. The introduction of HSCT has dramatically improved the prognosis of the disease. However, the mortality of the disease is still significantly high and a number of challenges remain to be addressed. Active disease at the time of the transplant is the major significant poor prognostic factor. Delayed diagnosis, after irreversible organ damage has occurred, especially neurological damage, disease reoccurrence and pre-transplant mortality, remain a concern.

Gene expression profiling of peripheral blood mononuclear cells from children with active hemophagocytic lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare, genetically heterogeneous autosomal recessive immune disorder that results when the critical regulatory pathways that mediate immune defense mechanisms and the natural termination of immune/inflammatory responses are disrupted or overwhelmed. To advance the understanding of FHL, we performed gene expression profiling of peripheral blood mononuclear cells from 11 children with untreated FHL. Total RNA was isolated and gene expression levels were determined using microarray analysis. Comparisons between patients with FHL and normal pediatric controls (n = 30) identified 915 down-regulated and 550 up-regulated genes with more than or equal to 2.5-fold difference in expression (P ≤ .05). The expression of genes associated with natural killer cell functions, innate and adaptive immune responses, proapoptotic proteins, and B- and T-cell differentiation were down-regulated in patients with FHL. Genes associated with the canonical pathways of interleukin-6 (IL-6), IL-10 IL-1, IL-8, TREM1, LXR/RXR activation, and PPAR signaling and genes encoding of antiapoptotic proteins were overexpressed in patients with FHL. This first study of genome-wide expression profiling in children with FHL demonstrates the complexity of gene expression patterns, which underlie the immunobiology of FHL.

Macrophage activation syndrome: advances towards understanding pathogenesis

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Macrophage activation syndrome in patients with systemic juvenile idiopathic arthritis is associated with MUNC13-4 polymorphisms

OBJECTIVE

Systemic juvenile idiopathic arthritis (JIA) is associated with macrophage activation syndrome. Macrophage activation syndrome bears a close resemblance to familial hemophagocytic lymphohistiocytosis (HLH). The development of familial HLH has been recently associated with mutations in MUNC13-4. The purpose of this study was to assess for possible sequence alterations in MUNC13-4 in patients with systemic JIA/macrophage activation syndrome.

METHODS

The MUNC13-4 sequence was analyzed in 18 unrelated patients with systemic JIA/macrophage activation syndrome, using 32 primer pair sets designed to amplify the 32 exons and at least 100 basepairs of the adjacent intronic regions. DNA samples obtained from 73 unrelated patients with systemic JIA and no history of macrophage activation syndrome and 229 unrelated healthy individuals were used as controls.

RESULTS

The biallelic sequence variants in MUNC13-4 reported in familial HLH were present in 2 of the 18 patients with JIA/macrophage activation syndrome. Further analysis of the MUNC13-4 sequences revealed an identical combination of 12 single-nucleotide polymorphisms (SNPs) in 9 of the remaining 16 patients with systemic JIA/macrophage activation syndrome (56%). Additional analysis suggested that these 12 SNPs (154[-19] g>a, 261[+26] c>g, 388[+81] g>a, 388[+122] c>t, 570[-60] t>g, 888 G>C, 1389[+36] g>a, 1992[+5] g>a, 2447[+144] c>t, 2599 A>G, 2830[+37] c>g, 3198 A>G) were inherited as an extended haplotype. In several patients, in addition to the described haplotype, there were other SNPs in the second allele of MUNC13-4. Moreover, 1 patient had a complex mutation with 2 changes, 2542 A>C and 2943 G>C, in a cis configuration. The haplotype was present in only 27 (12%) of 229 healthy control subjects (chi(2) = 23.5) and in 6 (8.2%) of 73 patients with systemic JIA and no history of macrophage activation syndrome.

CONCLUSION

The data suggest an association between MUNC13-4 polymorphisms and macrophage activation syndrome in patients with systemic JIA.

Failure of interferon gamma to induce the anti-inflammatory interleukin 18 binding protein in familial hemophagocytosis

Background

Familial hemophagocytosis (FHL) is a rare disease associated with defects in proteins involved in CD8⁺ T-cell cytotoxicity. Hyperactivation of immune cells results in a perilous, Th1-driven cytokine storm. We set out to explore the regulation of cytokines in an FHL patient who was clinically stable on low-dose immunosuppressive therapy after bone marrow transplantation over a six-month period. During this period, chimerism analyses showed that the fraction of host cells was between 1 and 10%. Both parents of the patient as well as healthy volunteers were studied for comparison.

Methods/Principal Findings

Using ELISA, quantitative real-time PCR, and clinical laboratory methods, we investigated constitutive and inducible cytokines, polymorphisms, and clinical parameters in whole blood and whole blood cultures. Although routine laboratory tests were within the normal range, the chemokines IP-10 and IL-8 as well as the cytokine IL-27p28 were increased up to 10-fold under constitutive and stimulated conditions compared to healthy controls. Moreover, high levels of IFNγ and TNFα were produced upon stimulation. Unexpectedly, IFNγ induction of IL-18 binding protein (IL-18BP) was markedly reduced (1.6-fold vs 5-fold in controls). The patient's mother featured intermediately increased cytokine levels, whereas levels in the father were similar to those in the controls.

Conclusions/Significance

Since IL-18 plays a major role in perpetuating hemophagocytosis, the failure of IFNγ to induce IL-18BP may constitute a fundamental pathogenetic mechanism. Furthermore, increased production of IL-8 and IL-27 appears to be associated with this disease. Such dysregulation of cytokines was also found in the heterozygous parents, providing a novel insight into genotype-phenotype correlation of FHL which may encourage future research of this rare disease.

UNC13D is the predominant causative gene with recurrent splicing mutations in Korean patients with familial hemophagocytic lymphohistiocytosis

BACKGROUND

Familial hemophagocytic lymphohistiocytosis is a fatal disease characterized by immune dysregulation from defective function of cytotoxic lymphocytes. Three causative genes have been identified for this autosomal recessive disorder (PRF1, UNC13D, and STX11). We investigated the molecular genetics of familial hemophagocytic lymphohistiocytosis in Korea.

DESIGN AND METHODS

Pediatric patients who fulfilled the HLH-2004 criteria were recruited from the Korean Registry for Histiocytosis. Molecular genetic studies were performed on the patients' DNA samples by direct sequencing of all coding exons and flanking sequences of PRF1, UNC13D, and STX11.

RESULTS

Forty patients were studied and familial hemophagocytic lymphohistiocytosis mutations were identified in nine; eight patients had UNC13D mutations (89%) and one had a mutation in PRF1. No patient had a STX11 mutation. Notably, four patients had only one UNC13D mutant allele, suggesting that the other mutation was missed by conventional direct sequencing. All UNC13D mutations were deleterious in nature. One known splicing mutation, c.754-1G>C, was recurrent, accounting for 58% of all the mutant alleles (7/12). Five UNC13D mutations were novel (p.Gln98X, p.Glu565SerfsX7, c.1993-2A>G, c.2367+1G>A, and c.2954+5G>A). The one patient with PRF1 mutation was homozygous for a frameshift mutation (p.Leu364GlufsX93), which was previously reported to be the most frequent PRF1 mutation in Japan.

CONCLUSIONS

This is the first investigation on the molecular genetics of familial hemophagocytic lymphohistiocytosis in Korea. The data showed that UNC13D is the predominant causative gene in the Korean population. The identification of mutations missed by conventional sequencing would better delineate the mutation spectrum and help to establish the optimal molecular diagnostic strategy for familial hemophagocytic lymphohistiocytosis in Korea, which might need an RNA-based screening strategy.

Comprehensive analyses and characterization of haemophagocytic lymphohistiocytosis in Vietnamese children

Haemophagocytic lymphohistiocytosis (HLH) is a fatal haematological disorder with diverse aetiology. This prospective study was undertaken to characterize HLH cases in Vietnamese children. Clinical and laboratory data, genetic analyses and outcome of the HLH patients were analysed. A total of 33 patients were enrolled from March 2007 to December 2008, with a median age of 3 years. Mutations of the SH2D1A (SAP) and PRF1 genes were detected in one patient, respectively. The virus association was high, up to 63.6% (21/33), including Epstein-Barr virus (19/33), cytomegalovirus (2/33) and dengue virus (2/33). Five patients had malignant lymphoma and two had autoimmune diseases. Twenty-eight patients were treated according to the HLH-2004 protocol. The first response rate was 64.3% (18/28), with an early death rate of 35.7% (10/28). High levels of interferon-gamma, interleukin-10, MIG and interferon-inducible protein-10 (IP-10) were associated with early mortality (P < 0.05). Reactivation among the responders was high (9/18) and the uneventful resolution was low (3/18) after a median follow-up of 35 weeks. In conclusion, the majority of HLH cases are associated with virus infections in Vietnamese children. Familial HLH is rare. The frequent reactivation and high mortality demands a more appropriate therapeutic regimen in tropical areas like Vietnam.

Macrophage activation syndrome: serological markers and treatment with anti-thymocyte globulin

Two patients presented at the University of Rochester Medical Center with a febrile illness, cytopenias, organ failure (liver failure or respiratory failure), and markedly elevated serum ferritin and sIL-2R. A diagnosis of probable macrophage activation syndrome was made. Both patients failed initial therapy with steroids and cyclosporine, either due to toxicity or lack of efficacy. Both patients responded dramatically to rabbit anti-thymocyte globulin (ATG).

Diagnostic challenges in a child with familial hemophagocytic lymphohistiocytosis type 3 (FHLH3) presenting with fulminant neurological disease

BACKGROUND

Familial hemophagocytic lymphohistiocytosis (FHLH) is an autosomal recessively inherited multisystem disease characterized by fever, rash, splenomegaly, cytopenias, and variable central nervous system (CNS) manifestations.

CASE HISTORY

We report the case of a 3-year-old boy who presented with splenomegaly and normocytic anemia 4 months after returning to the US from a region endemic for Leishmania infection. The child later developed progressive neurological impairment and had radiologic evidence of widespread demyelinating disease. Gene studies showed homozygosity for a mutation at Munc13-4, confirming FHLH type 3.

DISCUSSION

The diagnostic uncertainty that accompanies FHLH was compounded by our patient's travel history and CNS disease mimicking acute disseminated encephalomyelitis (ADEM). Diagnostic criteria for hemophagocytic lymphohistiocytosis were not consistently met, despite aggressive disease.

CONCLUSIONS

FHLH may present with fulminant demyelinating disease, mimicking ADEM, and without necessarily meeting previously defined clinical and laboratory criteria. We strongly recommend expeditious molecular testing and genetic counseling for FHLH mutations in cases of undiagnosed inflammatory CNS disease in the pediatric population.

Etanercept for therapy-resistant macrophage activation syndrome

Macrophage activation syndrome (MAS) is a severe, potentially fatal complication of childhood rheumatic diseases, especially systemic onset juvenile idiopathic arthritis (SoJIA). We report a 4-year-old girl with probable SoJIA who presented with MAS. She did not respond to pulse methyl prednisolone and Cyclosporine A (CsA). She also failed to respond to intravenous immunoglobulin (IVIG) therapy. Etanercept was started, based on the observation of increased serum levels of tumor necrosis factor-alpha (TNF-alpha) in patients with MAS. Her condition improved following etanercept, suggesting that etanercept might have a therapeutic role in resistant MAS.

Macrophage activation syndrome in 13 children with systemic-onset juvenile idiopathic arthritis

BACKGROUND

Macrophage activation syndrome (MAS) is a severe, potentially life-threatening condition induced by chronic rheumatic diseases, especially systemic-onset juvenile idiopathic arthritis (SoJIA) in childhood. This study aimed to analyze the clinical and laboratory characteristics of systemic-onset juvenile idiopathic arthritis (SoJIA) with macrophage activation syndrome (MAS) in 13 patients.

METHODS

Clinical and laboratory data of 13 SoJIA patients with MAS treated in our hospital from January 2003 to October 2007 were analyzed.

RESULTS

In the 13 patients, 9 were boys and 4 girls aged from 5 months to 12 years. Clinical manifestations were of no typical characteristics including persistent fever, anemia, arthritis, hepatosplenomegaly, lymph-adenopathy, dysfunction of the liver, abnormal fat metabolism, and hemophagocytic cells in the bone marrow. Two patients experienced acute respiratory distress syndrome, two had mutiorgan failure, and three died. The perforin A91V (NCBI:SNP rs35947132) gene in 6 patients was normal. Glucocorticoid and immunoimpressive therapy were effective in all patients and plasmapheresis used in one severe patient was also effective.

CONCLUSIONS

MAS is a serious complication of JIA, especially systemic-onset juvenile idiopathic arthritis. It is essentially important to recognize and treat MAS earlier in order to lower the mortality.

Tolerance and autoimmunity: lessons at the bedside of primary immunodeficiencies

The recent progress in the genetic characterization of many primary immunodeficiencies (PIDs) allows for a better understanding of immune molecular and cellular mechanisms. The present chapter discusses associations between PIDs and autoimmune diseases (AIDs) in this new light. PIDs are classified according to the frequency of association with AIDs, defining four groups of conditions: systematic (more than 80% of all patients), strong (10-80%), mild (less than 10%), and absent (no available descriptions). Several general conclusions could be drawn: (1) pathological autoimmune (AI) manifestations are very frequently associated with PIDs, indicating that, contrary to conventional notions, antimicrobial protection and natural tolerance to body tissues share many basic mechanisms; (2) in some gene defects, association is so strong that one could speak of "monogenic" AIDs; (3) basic types of PIDs are selectively associated with AID of a particular set of target tissues; (4) while for some gene defects, current theory satisfactorily explains pathogenesis of the corresponding AID, other situations suggest extensive gaps in the present understanding of natural tolerance; and (5) not exceptionally, observations on the AI phenotype for the same gene defect in mouse and man are not concordant, perhaps owing to the limited genetic diversity of mouse models, often limited to a single mouse strain. Overall, clinical observations on PID support the new paradigm of "dominant" tolerance to self-components, in which AID owes to deficits in immune responses (i.e., in regulatory mechanisms), rather than from excessive reactivity.