Induction of apoptosis and caspase activation in cells obtained from familial haemophagocytic lymphohistiocytosis patients

Severe congenital neutropenia-associated JAGN1 mutations unleash a calpain-dependent cell death programme in myeloid cells

Severe congenital neutropenia (SCN) of autosomal recessive inheritance, also known as Kostmann disease, is characterised by a lack of neutrophils and a propensity for life-threatening infections. Using whole-exome sequencing, we identified homozygous JAGN1 mutations (p.Gly14Ser and p.Glu21Asp) in three patients with Kostmann-like SCN, thus confirming the recent attribution of JAGN1 mutations to SCN. Using the human promyelocytic cell line HL-60 as a model, we found that overexpression of patient-derived JAGN1 mutants, but not silencing of JAGN1, augmented cell death in response to the pro-apoptotic stimuli, etoposide, staurosporine, and thapsigargin. Furthermore, cells expressing mutant JAGN1 were remarkably susceptible to agonists that normally trigger degranulation and succumbed to a calcium-dependent cell death programme. This mode of cell death was completely prevented by pharmacological inhibition of calpain but unaffected by caspase inhibition. In conclusion, our results confirmed the association between JAGN1 mutations and SCN and showed that SCN-associated JAGN1 mutations unleash a calcium- and calpain-dependent cell death in myeloid cells.

Case report: patient with unexplained high fever and pancytopenia

OBJECTIVE AND IMPORTANCE

We present a case of hemophagocytic lymphohistiocytosis (HLH), giving insight in how to establish diagnosis and start appropiate treatment.

CLINICAL PRESENTATION

A 45-year-old male presented at the emergency ward with high fever and pancytopenia. Repeat bone marrow aspirates showed hemophagocytosis. Extensive work-up with exclusion of other infectious and malignant diseases, eventually lead us to the diagnosis of hemophagocytic lymphohistiocytosis.

INTERVENTION

The patient was treated with Etoposide, Cyclosporine A, and systemic steroids based on the HLH-2004 protocol. Unfortunately the patient responded very poorly to the treatment with prolonged pancytopenia, leading to central hemorrhage and eventually death.

CONCLUSION

Diagnosis of hemopagocytic lymphohistiocytosis is difficult and late because of aspecific signs and low incidence. The HLH-criteria can be of use to exclude or confirm diagnosis in unclear cases. Early diagnosis and treatment is crucial given high morbidity and mortality. Therapy depends on type and etiology of the HLH-syndrome. Besides treating the possible triggering factor, Etoposide, steroids, and Cyclosporine A are the mainstays of treatment, sometimes followed by allogenic hematopoietic stem cell transplantation. More research in adults is needed.

Hemophagocytic lymphohistiocytosis complicated by multiorgan failure: A case report

RATIONALE

We present a case of hemophagocytic lymphohistiocytosis (HLH) with severe pulmonary complication and acute respiratory distress syndrome (ARDS) hospitalized in our intensive care unit (ICU) in 2014; distinctive trait of this case has been the challenging diagnosis, with a bone marrow biopsy always negative, the severe pulmonary complication with ARDS and severe pulmonary hypertension, and the ferritin temporal kinetics that precisely followed the clinical course of disease.

PATIENT CONCERNS

A 32-year-old woman from the Philippines first diagnosed with upper airway infection, was subsequently hospitalized in infectious disease department and treated for community acquired pneumonia.

DIAGNOSES

After clinical picture worsened with a profound respiratory insufficiency, the patient was intubated and transferred to our ICU. During this hospitalization, the clinical picture of fever, cutaneous rashes, lymphadenitis, hepatitis, leukopenia, anemia, hyperferritinemia, hypertriglyceridemia, high level of auto-antibodies, and low NK activity suggested an hemophagocytic lymphohistiocytosis syndrome, even if bone marrow biopsy was negative for hemophagocytosis.

INTERVENTIONS

Immunosuppressive therapy with dexamethasone and etoposide was started, and the patient was discharged from ICU 4 months after admission.

LESSONS

HLH is a rare disorder of the mononuclear phagocytic system, characterized by systemic proliferation of non- neoplastic histiocytes. The diagnosis is often challenging and not all of the diagnostic criteria may be present at the same time; this case shows how complex the diagnosis could be, how hematic ferritin levels could help in following the course of the disease, and the possibility of severe pulmonary complication either due to the disease itself and to possible sovra infections.

Confirmed efficacy of etoposide and dexamethasone in HLH treatment: long-term results of the cooperative HLH-2004 study

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome comprising familial/genetic HLH (FHL) and secondary HLH. In the HLH-94 study, with an estimated 5-year probability of survival (pSu) of 54% (95% confidence interval, 48%-60%), systemic therapy included etoposide, dexamethasone, and, from week 9, cyclosporine A (CSA). Hematopoietic stem cell transplantation (HSCT) was indicated in patients with familial/genetic, relapsing, or severe/persistent disease. In HLH-2004, CSA was instead administered upfront, aiming to reduce pre-HSCT mortality and morbidity. From 2004 to 2011, 369 children aged <18 years fulfilled HLH-2004 inclusion criteria (5 of 8 diagnostic criteria, affected siblings, and/or molecular diagnosis in FHL-causative genes). At median follow-up of 5.2 years, 230 of 369 patients (62%) were alive (5-year pSu, 61%; 56%-67%). Five-year pSu in children with (n = 168) and without (n = 201) family history/genetically verified FHL was 59% (52%-67%) and 64% (57%-71%), respectively (familial occurrence [n = 47], 58% [45%-75%]). Comparing with historical data (HLH-94), using HLH-94 inclusion criteria, pre-HSCT mortality was nonsignificantly reduced from 27% to 19% (P = .064 adjusted for age and sex). Time from start of therapy to HSCT was shorter compared with HLH-94 (P =020 adjusted for age and sex) and reported neurological alterations at HSCT were 22% in HLH-94 and 17% in HLH-2004 (using HLH-94 inclusion criteria). Five-year pSu post-HSCT overall was 66% (verified FHL, 70% [63%-78%]). Additional analyses provided specific suggestions on potential pre-HSCT treatment improvements. HLH-2004 confirms that a majority of patients may be rescued by the etoposide/dexamethasone combination but intensification with CSA upfront, adding corticosteroids to intrathecal therapy, and reduced time to HSCT did not improve outcome significantly.

Etoposide selectively ablates activated T cells to control the immunoregulatory disorder hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is an inborn disorder of immune regulation caused by mutations affecting perforin-dependent cytotoxicity. Defects in this pathway impair negative feedback between cytotoxic lymphocytes and APCs, leading to prolonged and pathologic activation of T cells. Etoposide, a widely used chemotherapeutic drug that inhibits topoisomerase II, is the mainstay of treatment for HLH, although its therapeutic mechanism remains unknown. We used a murine model of HLH, involving lymphocytic choriomeningitis virus infection of perforin-deficient mice, to study the activity and mechanism of etoposide for treating HLH and found that it substantially alleviated all symptoms of murine HLH and allowed prolonged survival. This therapeutic effect was relatively unique among chemotherapeutic agents tested, suggesting distinctive effects on the immune response. We found that the therapeutic mechanism of etoposide in this model system involved potent deletion of activated T cells and efficient suppression of inflammatory cytokine production. This effect was remarkably selective; etoposide did not exert a direct anti-inflammatory effect on macrophages or dendritic cells, and it did not cause deletion of quiescent naive or memory T cells. Finally, etoposide's immunomodulatory effects were similar in wild-type and perforin-deficient animals. Thus, etoposide treats HLH by selectively eliminating pathologic, activated T cells and may have usefulness as a novel immune modulator in a broad array of immunopathologic disorders.

Chemoimmunotherapy for hemophagocytic lymphohistiocytosis: long-term results of the HLH-94 treatment protocol

Hemophagocytic lymphohistiocytosis (HLH) used to have a dismal prognosis. We report the final results of HLH-94, the largest prospective diagnostic/therapeutic HLH study so far. The treatment includes immunosuppressive and cytotoxic therapy aiming at clinical remission, followed by HSCT in patients with familial, persistent, or recurrent disease. Altogether, 249 patients fulfilled inclusion criteria and started HLH-94 therapy (July 1994-December 2003); 227 (91%) were followed-up for ≥ 5 years. At 6.2 years median follow-up, estimated 5-year probability of survival was 54% ± 6%. Seventy-two patients (29%) died before HSCT, 64 within 1 year, 97% of whom had active disease. In 124 patients who underwent HSCT, 5-year survival was 66 ± 8%; tendency to increased survival (P = .064) in patients with nonactive disease at HSCT. Patients with familial disease had a 5-year survival of 50% ± 13%; none survived without HSCT. Patients deceased during the first 2 months more often had jaundice, edema, and elevated creatinine. Forty-nine patients (20%) were alive without signs of HLH activity and off-therapy > 1-year without HSCT; they presented at older age (P < .001), were more often female (P = .011), and less often had CNS disease (P < .001) or hepatomegaly (P = .007). To conclude, HLH-94 chemoimmunotherapy has considerably improved outcome in HLH. Collaborative efforts are needed to further reduce early mortality, HSCT-related mortality, and neurologic late effects.

Frequency and spectrum of central nervous system involvement in 193 children with haemophagocytic lymphohistiocytosis

Haemophagocytic lymphohistiocytosis (HLH) may cause meningoencephalitis and significant neurological sequelae. We examined the relationship between neurological symptoms and cerebrospinal fluid (CSF) at diagnosis, and long-term outcome, in all children enroled in the HLH-94-study prior to July 1, 2003, for whom information on CSF at diagnosis was available (n = 193). Patients were divided into four groups: (i) normal CSF (cells/protein) and no neurological symptoms (n = 71); (ii) normal CSF but neurological symptoms (n = 21); (iii) abnormal CSF but no symptoms (n = 50); and (iv) abnormal CSF with neurological symptoms (n = 51). At diagnosis, neurological symptoms were reported in 72/193 (37%) (seizures = 23); abnormal CSF in 101/193 (52%), and either or both in 122/193 (63%). Altogether 16/107 (15%) survivors had neurological sequelae at follow-up (median 5.3 years). Multivariate hazard ratios (HR) for mortality were 0.98 [95% confidence interval (CI) = 0.42-2.31], 1.52 (0.82-2.82) and 2.05 (1.13-3.72) for groups 2-4, compared with group 1. Moreover, sequelae were more frequent in group 4 (7/21, 33%) compared to groups 1-3 (9/86, 10%) (P = 0.015). Patients with abnormal CSF at diagnosis had significantly increased mortality [HR = 1.78 (95% CI = 1.08-2.92), P = 0.023]. Thus, a substantial proportion of HLH survivors suffer neurological sequelae, and children with abnormal CSF have increased risk of mortality and neurological sequelae. Prompt treatment of HLH at onset or relapse may reduce these complications.

Immunotherapy of familial hemophagocytic lymphohistiocytosis with antithymocyte globulins: a single-center retrospective report of 38 patients

OBJECTIVES

Familial hemophagocytic lymphohistiocytosis is a genetically determined condition that is characterized by unremitting CD8 T lymphocyte and macrophage activation and leads to death in the absence of therapy. On the basis of the immunologic pathophysiology of familial hemophagocytic lymphohistiocytosis, we propose a therapy with a combination of antithymocyte globulins with corticosteroids, cyclosporin A, and intrathecal injections of methotrexate.

METHODS

We retrospectively analyzed the outcome of antithymocyte globulin-based therapy that was performed in 38 consecutive patients who had familial hemophagocytic lymphohistiocytosis and were treated in a single center between 1991 and 2005. Overall, they received 45 courses of antithymocyte globulin (5-10 mg/kg per day for 5 days).

RESULTS

This regimen was associated with infections after 10 of 45 courses of antithymocyte globulin. There were 6 events after 11 antithymocyte globulin courses given as second-line therapy against 4 after 34 antithymocyte globulin courses in patients who were treated primarily with antithymocyte globulin. Antithymocyte globulin administration led to rapid and complete response of familial hemophagocytic lymphohistiocytosis in 73% of cases, partial response in 24%, and no response only once. When hematopoietic stem cell transplantation was performed early after complete or partial response induction, it led to a high rate of cure, in 16 of 19 cases. Overall survival was 21 of 38 with 4 toxic deaths.

CONCLUSION

Antithymocyte globulin based immunotherapy of familial hemophagocytic lymphohistiocytosis is efficient and carries an acceptable toxicity when used as a first treatment of familial hemophagocytic lymphohistiocytosis.

Mitochondrial nitric oxide in the signaling of cell integrated responses

Mitochondria are the specialized organelles for energy metabolism, but, as a typical example of system biology, they also activate a multiplicity of pathways that modulate cell proliferation and mitochondrial biogenesis or oppositely promote cell arrest and programmed cell death by a limited number of oxidative or nitrosative reactions. These reactions are influenced by matrix nitric oxide (NO) steady-state concentration, either from local production or by gas diffusion to mitochondria from the canonical sources. Likewise, in a range of ∼30–200 nM, NO turns mitochondrial O2utilization down by binding to cytochrome oxidase and elicits a burst of superoxide anion and hydrogen peroxide that diffuses outside mitochondria. Depending on NO levels and antioxidant defenses, more or less H2O2accumulates in cytosol and nucleus, and the resulting redox grading contributes to dual activation of proliferating and proapoptotic cascades, like ERK1/2 or p38 MAPK. Moreover, these sequential activating pathways participate in rat liver and brain development and in thyroid modulation of mitochondrial metabolism and contribute to hypothyroid phenotype through complex I nitration. On the contrary, lack of NO disrupts pathways like S-nitrosylation or H2O2production and likewise is a gateway to disease in amyotrophic lateral sclerosis with superoxide dismutase 1 mutations or to cancer proliferation.

HLH-2004: Diagnostic and therapeutic guidelines for hemophagocytic lymphohistiocytosis

In HLH-94, the first prospective international treatment study for hemophagocytic lymphohistiocytosis (HLH), diagnosis was based on five criteria (fever, splenomegaly, bicytopenia, hypertriglyceridemia and/or hypofibrinogenemia, and hemophagocytosis). In HLH-2004 three additional criteria are introduced; low/absent NK-cell-activity, hyperferritinemia, and high-soluble interleukin-2-receptor levels. Altogether five of these eight criteria must be fulfilled, unless family history or molecular diagnosis is consistent with HLH. HLH-2004 chemo-immunotherapy includes etoposide, dexamethasone, cyclosporine A upfront and, in selected patients, intrathecal therapy with methotrexate and corticosteroids. Subsequent hematopoietic stem cell transplantation (HSCT) is recommended for patients with familial disease or molecular diagnosis, and patients with severe and persistent, or reactivated, disease. In order to hopefully further improve diagnosis, therapy and biological understanding, participation in HLH studies is encouraged.

Newborn infant with hemophagocytic lymphohistiocytosis and generalized skin eruptions

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease resulting from abnormal proliferation of histiocytes in tissues and organs. The incidence of HLH is 1:50,000-300,000. Cutaneous eruptions have been reported in 6-65% of the cases. It's important to differentiate the eruptions from other systemic diseases. We present an infant with prominent skin manifestations of HLH. On the 11th day of life, she was admitted to our hospital with complaint of a generalized rash that had started the previous day. The eruptions consisted of irregularly shaped maculopapular erythematous rash and purpura. Bone marrow aspiration on the 25th day of life revealed hemophagocytosis with increased macrophages and histiocytes, consistent with HLH. Treatment was started with dexamethasone followed by induction chemotherapy with etoposide. All skin manifestations resolved in a few days. Although the clinical features are nonspecific, HLH should be kept in mind as an accompanying disease in neonates presenting with skin eruptions.

Spectrum and clinical implications of syntaxin 11 gene mutations in familial haemophagocytic lymphohistiocytosis: association with disease-free remissions and haematopoietic malignancies

OBJECTIVE

To determine the frequency and spectrum of mutations in the gene encoding syntaxin 11 (STX11) in familial haemophagocytic lymphohistiocytosis (FHL), a rare autosomal recessive disorder of immune dysregulation characterised by a defect in natural killer cell function.

METHODS

Mutational analysis of STX11 by direct sequencing was done in 28 FHL families that did not harbour perforin mutations, previously identified in some FHL patients. A detailed investigation of clinical features of these patients was also undertaken.

RESULTS

Two different STX11 mutations were identified, one nonsense mutation and one deletion, affecting six of 34 children in four of 28 unrelated PRF1 negative families. Both mutations have been reported before. Three patients experienced long periods (> or = 1 year) in remission without specific treatment, which is very uncommon in this disease. Despite the milder phenotype, some children with STX11 mutations developed severe psychomotor retardation. Two of the six patients harbouring STX11 gene defects developed myelodysplastic syndrome (MDS) or acute myelogenous leukaemia (AML).

CONCLUSIONS

STX11 gene mutations were found in 14% of the PRF1 negative FHL families included in the present cohort. These results suggest that STX11 gene mutations may be associated with secondary malignancies (MDS/AML), and that there is segregation of specific clinical features in FHL patients with an underlying genotype.

Cytotoxic therapy for severe avian influenza A (H5N1) infection

The mortality rate in documented avian influenza A virus subtype H5N1 infection is still high, which is currently reported by WHO at about 50%. Post-mortem analyses in affected patients have revealed haemophagocytosis similar to that found in patients with haemophagocytic lymphohistiocytosis (HLH); such haemophagocytosis could be a very prominent post-mortem feature in H5N1 infection. There are also clinical similarities between H5N1 infection and HLH, such as massive hypercytokinaemia, cytopenia, and acute encephalitis. Importantly, patients with another severe viral infection that may be complicated by secondary HLH, severe Epstein-Barr-virus-associated HLH, have significantly better survival if specific HLH therapy (including the cytotoxic and pro-apoptotic drug etoposide) is initiated early, with survival reported to rise from about 50% to 90%. With this notable improvement in survival, specific HLH treatment, including cytotoxic therapy, could be considered in patients with severe avian influenza A infection complicated by secondary HLH.

Subtyping of natural killer cell cytotoxicity deficiencies in haemophagocytic lymphohistocytosis provides therapeutic guidance

The familial form of haemophagocytic lymphohistiocytosis (HLH) is a fatal disease, with allogeneic stem cell transplantation (SCT) being the only curative treatment. In contrast, patients with secondary (infection-associated) HLH usually do not require SCT. Since it often is difficult to distinguish primary and secondary HLH, we wanted to identify a tool that provides guidance on whether SCT is required. The clinical outcome of 65 HLH patients was analysed in relation to the recently reported four types of defects in natural killer (NK)-cell cytotoxicity in HLH. None (0%) of the 36 patients with NK-cell deficiency type 3 attained a sustained (1-year) remission after stopping therapy without receiving SCT, in contrast to 45% (13/29) non-type 3 patients (P < 0.001). Most type 3 patients (22/36) underwent SCT (14/22, 64% are alive), whereas 11 of 14 that did not receive SCT died, and the three others had received HLH-therapy during the last year of follow-up. Of 54 patients analysed for perforin expression and/or mutation, the five with perforin deficiency were all type 3 patients. The data suggests that HLH patients with NK-cell deficiency type 3 will probably require SCT to survive. Thus, NK-cell deficiency classification may provide valuable guidance in judging whether an HLH-patient needs SCT.

Perforin and lymphohistiocytic proliferative disorders

Perforin is critical for cytotoxicity mediated by granules present in natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). Perforin-deficient mice have impaired cytotoxicity by NK cells and CTLs, resulting in failure to control infections with certain viruses or bacteria. Infection of perforin-deficient mice with lymphocytic choriomeningitis virus results in haemophagocytic lymphohistiocytosis and elevated levels of pro-inflammatory cytokines. Mutations throughout the perforin gene have been identified in patients with familial haemophagocytic lymphohistiocytosis (FHL) type 2. These patients present with fever, hepatosplenomegaly, pancytopenia, have marked elevations of T-helper type 1 and type 2 cytokines, and have impaired NK cell and CTL cytotoxicity. A number of infectious pathogens have been implicated as triggering the onset of disease. Identification of mutations in perforin as the cause of FHL should allow prenatal diagnosis of the disorder. While stem cell transplantation is curative, gene therapy might be effective in the future.

Kostmann syndrome: severe congenital neutropenia associated with defective expression of Bcl-2, constitutive mitochondrial release of cytochrome c, and excessive apoptosis of myeloid progenitor cells

Kostmann syndrome, or severe congenital neutropenia (SCN), is an autosomal recessive disorder of neutrophil production. To investigate the potential role of apoptosis in SCN, bone marrow aspirates and biopsies were obtained from 4 patients belonging to the kindred originally described by Kostmann and 1 patient with SCN of unknown inheritance. An elevated degree of apoptosis was observed in the bone marrow of these patients, and a selective decrease in B-cell lymphoma-2 (Bcl-2) expression was seen in myeloid progenitor cells. Furthermore, in vitro apoptosis of bone marrow-derived Kostmann progenitor cells was increased, and mitochondrial release of cytochrome c was detected in CD34+ and CD33+ progenitors from patients, but not in controls. Administration of granulocyte colony-stimulating factor (G-CSF) restored Bcl-2 expression and improved survival of myeloid progenitor cells. In addition, cytochrome c release was partially reversed upon incubation of progenitor cells with G-CSF. In sum, these studies establish a role for mitochondria-dependent apoptosis in the pathogenesis of Kostmann syndrome and yield a tentative explanation for the beneficial effect of growth factor administration in these patients. (Blood. 2004;103:3355-3361)

Human primary immunodeficiency diseases: a perspective

Primary immunodeficiency diseases consist of a group of more than 100 inherited conditions, mostly monogenic, predisposing individuals to different sets of infections, allergy, autoimmunity and cancer. Primary immunodeficiencies therefore represent exquisite models of various immunopathological settings. The identification of the associated genes, 100 so far, has generated a plethora of information about the immune system and spurred the analysis of many aspects of the development, function and regulation of both innate and adaptive immunity. These findings can potentially contribute to improved care of affected individuals by providing new diagnostic and/or therapeutic tools.

Engraftment and dissemination of T lymphocytes from primary haemophagocytic lymphohistiocytosis in scid mice

Although primary haemophagocytic lymphohistiocytosis (HLH) is a genetic disorder of T lymphocytes, it remains unclear why T lymphocytes of primary HLH patients preferentially infiltrate the central nervous system and peripheral blood, in addition to the reticuloendothelial systems. We engrafted Herpesvirus saimiri (HVS)-immortalized T-lymphocyte lines established from primary HLH patients into severe combined immunodeficient (scid) mice and examined their capacity to infiltrate mouse organs. A diffuse infiltration of human T lymphocytes was detected in each organ of scid mice treated with 1 x 10(6) T lymphocytes from all four primary HLH patients assessed, whereas no infiltration of T lymphocytes from healthy individuals was observed in any organ. The infiltration of T lymphocytes was mainly observed in the lung, brain and peripheral blood, in association with haemophagocytosis. These cells were positive for HLA-DR, CD3 and either CD8 or CD4, but negative for CD68. Certain markers of proliferation and apoptotic activities were highly positive in these cells. There was no difference between the infiltration pattern of T lymphocytes of primary HLH patients with a perforin deficiency and those without. By Southern blot analysis, T lymphocytes infiltrating mouse organs were observed to be polyclonal. These findings suggest that our murine model implementing HVS-immortalized human T lymphocytes is suitable to clarify the pathogenesis of primary HLH.

Biology and treatment of familial hemophagocytic lymphohistiocytosis: importance of perforin in lymphocyte-mediated cytotoxicity and triggering of apoptosis

Familial hemophagocytic lymphohistiocytosis (FHL) is, without treatment, an invariably fatal disease of infancy and early childhood characterized by fever, hepatosplenomegaly, pancytopenia, and a widespread accumulation of T-lymphocytes and macrophages. During recent years, the diagnosis and the survival as well as the understanding of the disease have improved dramatically. Recent studies suggest that FHL is caused by impaired lymphocyte-mediated cytotoxicity and defective triggering of apoptosis, and that the symptoms are mediated by a pro-inflammatory hypercytokinemia. Moreover, specific genetic alterations, mutations in the perforin gene, have been revealed in FHL patients. Perforin, which normally is secreted from cytotoxic T-lymphocytes and natural killer (NK) cells upon conjugation between effector and target cells, is able to insert into the membrane of the target cell. It there polymerizes to form a cell death-inducing pore through which toxic granzymes may enter the cell and trigger apoptosis. The establishment of perforin deficiency as a cause of the rapidly fatal disease FHL has demonstrated the essential role of perforin in human immune homeostasis.

Recent developments in the management of haemophagocytic lymphohistiocytosis

Over the past two decades, the underlying pathophysiology of haemophagocytic lymphohistiocytosis (HLH) (synonyms: haemophagocytic syndrome, macrophage activation syndrome) has been well recognised. Cytokine storm plays a major role, which derives from an inappropriate immune reaction caused by proliferating and activated T-cell or natural killer (NK) cells associated with macrophage activation and inadequate apoptosis of immunogenic cells. Many biological parameters reflecting activity of disease or response to treatment have been identified, in particular, serum ferritin has been confirmed to be one of the markers for HLH. The common types of HLH consist of non-hereditary (acquired) infection-associated disease such as Epstein-Barr virus (EBV)-haemophagocytic lymphohistiocytosis (HLH) and hereditary (familial) disease such as FHL, in which, at the molecular level, dysfunctional perforin was clarified. Regarding the therapeutic strategies, prompt differential diagnosis of underlying disease is essential and choice of treatment should be based on the risk (low or high) of prognosis, where either cyclosporin A, steroids or iv. immunoglobulin (IVIG) may be indicated as initial treatment for low-risk patients, with etoposide-containing regimens for high-risk patients. Significant improvement of prognosis has been obtained by incorporating intensive supportive care at the disease onset and prompt introduction of immunosuppressants to control cytokine storm. Subsequent immunochemotherapy and haemopoietic stem cell transplantation have contributed significantly to further improve survival of hereditary and refractory HLH patients.

Familial hemophagocytic lymphohistiocytosis: too little cell death can seriously damage your health

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare and fatal disease of early childhood characterized by a non-malignant accumulation of activated T lymphocytes and histiocytes in the reticuloendothelial system. Moreover, immune system derangement, with prominent hypercytokinemia and low or absent cytotoxic T and natural killer (NK) cell activity, is a consistent feature of this autosomal recessive disorder. Recent work has demonstrated that the degree of spontaneous caspase activation in FHL lymphocytes is attenuated in vitro whereas Fas-mediated caspase activation and apoptosis induction remains unmitigated, and FHL can thus be distinguished from the related chronic disorder of immune regulation termed autoimmune lymphoproliferative syndrome or ALPS. However, subsequent studies have identified mutations in the gene encoding perforin, a cytotoxic granule constituent required for apoptotic killing of target cells, in a number of FHL patients. Hence, the underlying defect in FHL may be conceived of as a lack of apoptosis triggering within the immune system, rather than apoptosis resistance per se. These observations represent an important step in our understanding of the pathogenesis of FHL and also serve to emphasize the pivotal role of cellular (perforin-based) cytotoxicity in the regulation of immune homeostasis.

Effect of alisol B acetate, a plant triterpene, on apoptosis in vascular smooth muscle cells and lymphocytes

Glucocorticoid-induced apoptosis is a well-recognized physiological regulator of T-cell number and function. Alisol B acetate, a triterpene from Alisma Plantago-aquatica, has a glucocorticoid-like structure, and may have a similar function like glucocorticoid-induced apoptosis in both vascular smooth muscle cell line (A7r5) and human acute lymphoblastic leukemia cell line (CEM cells). For exploring its mechanism, mitochondria membrane potential and apoptosis-related gene expression were discussed. Alisol B (10(-6)-10(-4) M) inhibited serum-stimulated DNA synthesis in a concentration-dependent manner (IC50) = 4.0 +/- 0.8 x 10(-6) M in A7r5 and 2.1 +/- 1.2 x 10(-6) M in CEM cells). The cell viability was reduced at 10(-4) M of alisol B. Similar results were seen in dexamethasone treatment (a synthetic glucocorticoid, 10(-6) M, 48 h). Apoptosis was induced after the cells were exposed to 10(-5)-10(-4) M alisol B or 10(-6) M dexamethasone for 48 h. The mitochondrial membrane potential (delta psi(m)) was significantly reduced after the alisol B treatment, indicating that the mitochondria might play a role in the alisol B induced cell apoptosis. Alisol B (10(-5)-10(-4) M) increased the levels of c-myc and bax mRNA and proteins, but not on the anti-apoptotic proto-oncogene, bcl-2, in A7r5 and CEM cells. In contrast, dexamethasone (10(-6) M) treatment only caused significant increase in c-myc mRNA levels. These results suggest that the increased ratio of Bax/Bcl-2 and the decreased mitochondrial membrane potential might be involved in the mechanisms of alisol B-induced cell apoptosis.

Spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive disease of early childhood characterized by nonmalignant accumulation and multivisceral infiltration of activated T lymphocytes and histiocytes (macrophages). Cytotoxic T and natural killer (NK) cell activity is markedly reduced or absent in these patients, and mutations in a lytic granule constituent, perforin, were recently identified in a number of FHL individuals. Here, we report a comprehensive survey of 34 additional patients with FHL for mutations in the coding region of the perforin gene and the relative frequency of perforin mutations in FHL. Perforin mutations were identified in 7 of the 34 families investigated. Six children were homozygous for the mutations, and one patient was a compound heterozygote. Four novel mutations were detected: one nonsense, two missense, and one deletion of one amino acid. In four families, a previously reported mutation at codon 374, causing a premature stop codon, was identified, and, therefore, this is the most common perforin mutation identified so far in FHL patients. We found perforin mutations in 20% of all FHL patients investigated (7/34), with a somewhat higher prevalence, approximately 30% (6/20), in children whose parents originated from Turkey. No other correlation between the type of mutation and the phenotype of the patients was evident from the present study. Our combined results from mutational analysis of 34 families and linkage analysis of a subset of consanguineous families indicate that perforin mutations account for 20%-40% of the FHL cases and the FHL 1 locus on chromosome 9 for approximately 10%, whereas the major part of the FHL cases are caused by mutations in not-yet-identified genes.

Perforin gene defects in familial hemophagocytic lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare, rapidly fatal, autosomal recessive immune disorder characterized by uncontrolled activation of T cells and macrophages and overproduction of inflammatory cytokines. Linkage analyses indicate that FHL is genetically heterogeneous and linked to 9q21.3-22, 10q21-22, or another as yet undefined locus. Sequencing of the coding regions of the perforin gene of eight unrelated 10q21-22-linked FHL patients revealed homozygous nonsense mutations in four patients and missense mutations in the other four patients. Cultured lymphocytes from patients had defective cytotoxic activity, and immunostaining revealed little or no perforin in the granules. Thus, defects in perforin are responsible for 10q21-22-linked FHL. Perforin-based effector systems are, therefore, involved not only in the lysis of abnormal cells but also in the down-regulation of cellular immune activation.

All along the watchtower: on the regulation of apoptosis regulators

Members of the expanding family of Bcl-2-like proteins have emerged as important regulators of programmed cell death, and recent studies have unearthed numerous mechanisms for regulating the function of these death agonists and antagonists. In addition to the transcriptional control of gene expression, these mechanisms include posttranslational events such as phosphorylation, proteolysis, and the induction of conformational changes, which may either activate or inactivate these molecules. Interaction with homologous and nonhomologous proteins and specific subcellular targeting of Bcl-2-like proteins are other means of fine-tuning the cellular response to noxious stimuli. Recently, considerable attention has turned to the regulation of so-called BH3-only molecules, which appear to act as stress sensors that relay signals to other pro- or antiapoptotic family members. We discuss how the regulation of these apoptosis regulators may control the ultimate fate of the cell.