Establishment of a reference interval for natural killer cell activity through flow cytometry and its clinical application in the diagnosis of hemophagocytic lymphohistiocytosis

A comprehensive battery of flow cytometric immunoassays for the in vitro testing of chemical effects in human blood cells

Background

There is a growing need for immunological assays to test toxic and modulatory effects of chemicals. The assays should be easy to use, reproducible and superior to cell line-based assays. We have therefore developed a comprehensive portfolio of assays based on primary human blood cells that are suitable for testing chemical effects.

Methods

The flow cytometry-based assays were designed to target a wide range of human peripheral blood mononuclear cells and whole blood, including T cells, NK cells, B cells, basophils and innate-like T cells such as γδT, MAIT and NKT cells. We have selected a set of activation markers for each immune cell, e.g: CD154 (T cells), CD137, CD107a (NK cells), CD63 (basophils), CD69, CD83 (B cells), CD69, IFN-γ (MAIT cells) and we selected cell specific stimuli: aCD3 antibodies (T cells); E. coli and cytokines IL-12/15/18 (MAIT cells); CpG ODN2006, R848 or aCD40 antibodies (B cells), fMLP or aFcϵR1 (basophils) or K562 cells (NK cells).

Results

By selecting immune cell-specific markers and cell-specific stimuli, we were able to induce particular immune responses from the targeted immune cells. For example, the response to stimulation with anti-CD3 antibodies was in 36.8% of CD107a+CD8+ cells. Cytokine stimulation induced the production of IFN-γ in 30% of MAIT cells. After stimulation with E. coli, around 50% of MAIT cells produced TNF. About 40% of basophils responded to aFcƐR1 stimulation. Similar activation ranges were achieved in K562-stimulated NK cells.

Conclusion

Our test portfolio covers the most relevant immune cells present in human blood, providing a solid basis for in vitro toxicity and immunomodulatory testing of chemicals. By using human blood, the natural composition of cells found in the blood can be determined and the effects of chemicals can be detected at the cellular level.

Integrative Magneto-Microfluidic Separation of Immune Cells Facilitates Clinical Functional Assays

Accurately analyzing the functional activities of natural killer (NK) cells in clinical diagnosis remains challenging due to their coupling with other immune effectors. To address this, an integrated immune cell separator is required, which necessitates a streamlined sample preparation workflow including immunological cell isolation, removal of excess red blood cells (RBCs), and buffer exchange for downstream analysis. Here, a self-powered integrated magneto-microfluidic cell separation (SMS) chip is presented, which outputs high-purity target immune cells by simply inputting whole blood. The SMS chip intensifies the magnetic field gradient using an iron sphere-filled inlet reservoir for high-performance immuno-magnetic cell selection and separates target cells size-selectively using a microfluidic lattice for RBC removal and buffer exchange. In addition, the chip incorporates self-powered microfluidic pumping through a degassed polydimethylsiloxane chip, enabling the rapid isolation of NK cells at the place of blood collection within 40 min. This chip is used to isolate NK cells from whole blood samples of hepatocellular cancer patients and healthy volunteers and examined their functional activities to identify potential abnormalities in NK cell function. The SMS chip is simple to use, rapid to sort, and requires small blood volumes, thus facilitating the use of immune cell subtypes for cell-based diagnosis.

Current status of the diagnosis and treatment of hemophagocytic lymphohistiocytosis in adults

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of defective apoptosis, a disruption of the regulatory pathway that terminates immune and inflammatory responses. Fever, cytopenia, splenomegaly, and/or hemophagocytosis are typical findings of this syndrome. HLH can be induced by genetic disorders (familial) or secondary causes. Familial HLH is rare, while secondary causes in adults include infection, autoimmunity, and malignancy. HLH in adults tends to be confused with or misdiagnosed as sepsis, mainly due to similar clinical manifestations and laboratory findings, which make it difficult to diagnose HLH rapidly and adopt immunosuppressive agents and/or chemotherapy adequately. Treatment of pediatric HLH using HLH-2004 or multi-agent chemotherapy can be applied in adult patients, although the dose and type of drug need to be adjusted. It is highly recommended that allogenic hematopoietic stem cell transplantation should be used in patients who become reactivated or are refractory to the initial treatment as soon as possible to improve survival. Future clinical trials are warranted to determine more suitable treatments for adult patients with HLH.

Clinical, immunological and genetic findings in patients with UNC13D deficiency (FHL3): A systematic review

BACKGROUND

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare autosomal recessive immune disorder that is caused by mutations in 6 different genes related to the formation and function of secretory lysosomes within cytotoxic T lymphocytes and natural killer (NK) cells. Thus, defect in these genes is associated with the accumulation of antigens due to defective cytotoxic function. FHL type 3 (FHL3) accounts for nearly 30-40% of FHL, and its underlying reason is mutation in UNC13D gene which encodes Munc13-4 protein.

METHODS

For the first time, we aimed to systematically review clinical features, immunologic data, and genetic findings of patients with FHL3. We conducted electronic searches for English-language articles in PubMed, Web of Science, EMBASE, and Scopus databases to collect comprehensive records related to patients with UNC13D mutations.

RESULTS

A total of 279 abstracts were initially reviewed for inclusion. Among them, 57 articles corresponding to 322 individual FHL3 patients fulfilled our selection criteria. Finally, 73 and 249 patients were considered as severe and mild feature groups, respectively. Our results confirmed that fever, hepatosplenomegaly, and hemophagocytosis are common clinical features in the disease. Moreover, reduced fibrinogen and NK cell activity, as well as increased ferritin and triglycerides, are important markers for early diagnosis of the FHL3 disease. Investigation of genotype showed that the most prevalent type and zygosity of UNC13D are splice-site errors and compound heterozygous, respectively.

CONCLUSION

FHL3 patients have a wide range of clinical manifestations, which makes it difficult to diagnose. Therefore, it seems that the sequencing of the entire UNC13D gene (coding and non-coding regions) is the most appropriate way to accurate diagnosis of FHL3 patients.

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

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

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

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

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

Genotype characteristics and immunological indicator evaluation of 311 hemophagocytic lymphohistiocytosis cases in China

Background

Primary hemophagocytic lymphohistiocytosis (pHLH) is a genetic disorder that is classically diagnosed by genetic testing. Secondary HLH (sHLH) is usually caused by infections, malignancies, or autoimmune disorders, but may display some mutations or polymorphisms. Rapid immunological assays examining natural killer (NK) cell activity, degranulation function (CD107a), and protein expression related to genetic deficiencies have been recommended for early pHLH identification.

Methods

A retrospective analysis of 311 HLH patients from a Chinese population was performed to evaluate the potential correlations between genetic testing and rapid immunological assays; genotyping characteristics, age of onset, and etiology were examined.

Results

Among the 128 (128/311) patients who were positive in the genetic screening, the most frequently detected mutant gene was UNC13D (29%), followed by LYST (21%), PRF1 (17%), and STXBP2 (10%). Among pHLH patients (n = 39), the majority (67%) had PRF1 and UNC13D defects. FHL-2 was predominant (12/27, 44%) in patients aged under 18, while FHL-3 was the most common (6/12, 50%) in adults. Differences in genetic variant types and etiological components were noted in HLH patients based on the age of onset. NK cell activity and CD107a were observed to show a consistent trend (P_trend < 0.001) when grouping patients according to the severity of the genetic variant type. Moreover, NK cell activity was generally consistent within a certain range of ΔCD107a values (P_trend < 0.001). The PPV for bi-allelic degranulation gene mutations in patients with CD107a < 5% was 38.9% (7/18), while the PPV in patients with CD107a ≤10% was 16.7% (13/78). The PPV for pHLH was 41.4% (29/70) with NK cell activity ≤13%. To further evaluate the diagnostic efficacy of NK cell activity assay in pHLH, a receiver operating characteristic (ROC) curve was generated and showed an area under the curve (AUC) of 0.872, and the optimal cutoff value was determined to be 13.425% with a sensitivity of 84.21% and specificity of 80.67% when the corresponding Youden index was maximized. Flow cytometry screening for deficient proteins, including perforin, SAP, and XIAP, showed a relatively high sensitivity (83.33–93.33%). The positive predictive values (PPVs) of perforin and XIAP were relatively low (20.83–26.92%), but the negative predictive values (NPVs) for all three were excellent (all > 98%).

Conclusions

Various immunological indicators have different clinical prediction and application values for the diagnosis of pHLH. The degree of reduction of immunological indicators also needs attention, and choosing appropriate cutoff value may be of important significance in guiding clinical judgment for pHLH.

Evaluation of lymphocyte function by IFN-γ secretion capability assay in the diagnosis of lymphoma-associated hemophagocytic syndrome

Lymphoma-associated hemophagocytic syndrome (LAHS) is a highly life-threatening disease characterized by an uncontrolled immune disorder. Both under-recognition and delayed diagnosis may contribute to aggressive diseases, and a poorer prognosis. Identification of laboratory features specific for LAHS patients may allow for early detection and intervention with improved outcomes. In the present study, 120 lymphoma patients at first diagnosis were recruited and the function of lymphocytes was evaluated by IFN-γ secretion assay at first diagnosis and follow up. During the surveillance period, 20 patients who complicated with hemophagocytic lymphohistiocytosis (HLH) were classified as LAHS group, and 30 patients without infectious diseases during the course of treatment were classified as lymphoma control group. In addition, 20 non-malignant associated HLH patients recruited as HLH control group and 50 healthy control (HC) subjects were also included. The IFN-γ secretion capability of lymphocytes was compared between first diagnosis of lymphoma patients who was complicate with HLH or not in the disease progression. Our results showed that only NK cell activity was decreased in lymphoma control group, but the activities of NK, CD4+ and CD8+ T cells were all significantly decreased at the time of lymphoma diagnosis in those who would progress with HLH. During the course of treatment, lymphocyte function was relatively stable in lymphoma patients but became further decreased when suffering from complication of LAHS. The IFN-γ secretion capability of lymphocytes in LAHS and non-malignant associated HLH patients were all significantly decreased compared with HCs. So the occurrence of HLH was the key factor leading to the impaired activity of lymphocytes. These data suggest that decreased lymphocyte function might be used as a predictor of LAHS, which has critical clinical significance in diagnosis and further understanding the pathogenesis of the disease.

Establishment of the Reference Intervals of Lymphocyte Function in Healthy Adults Based on IFN-γ Secretion Assay upon Phorbol-12-Myristate-13-Acetate/Ionomycin Stimulation

The function of lymphocytes is the key to reflect the immune status of hosts. Evaluation of lymphocyte function is a useful tool to monitor the effect of immunosuppressive treatment and predict the prognosis of immune-mediated diseases (e.g., cancer, autoimmune diseases, and infectious diseases). As the lymphocytes have various activities, such as activation, cytotoxicity, and cytokine secretion, it is a challenge to evaluate the function of lymphocytes in clinical practice and the reference intervals (RIs) of lymphocyte function are rarely reported. The present study showed that the secretion of IFN-γ was well correlated with the activation, chemotaxis, and cytotoxicity of CD4⁺, CD8⁺ T cells, and NK cells, which suggests that IFN-γ production can be used as a symbol of lymphocyte function. We therefore created a simple method to detect the function of CD4⁺, CD8⁺ T cells, and NK cells simultaneously according to IFN-γ secretion by using whole blood instead of peripheral blood mononuclear cells. We further established the RIs of lymphocyte function (CD4⁺ T cells: 15.31-34.98%; CD8⁺ T cells: 26.11-66.59%; NK cells: 39.43-70.79%) in healthy adults. This method showed good reproducibility for the evaluation of lymphocyte function. The established RIs were suitable for use in other centers based on the validation data. We also validated the RIs in individuals with different immune status, and the results showed that kidney transplant recipients and infants (0-1 year) had a decreased lymphocyte function, whereas T cells in systemic lupus erythematosus patients exhibited an opposite trend. Overall, we have successfully established the RIs of lymphocyte function in healthy adults in a simple way, which might be of important clinical value in the diagnosis, monitoring, and prognosis of immune-related diseases.

Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis is a life-threatening disorder characterized by unbridled activation of cytotoxic T lymphocytes, natural killer (NK) cells, and macrophages resulting in hypercytokinemia and immune-mediated injury of multiple organ systems. It is seen in both children and adults and is recognized as primary (driven by underlying genetic mutations that abolish critical proteins required for normal function of cytotoxic T cells and NK cells) or secondary (resulting from a malignant, infectious, or autoimmune stimulus without an identifiable underlying genetic trigger). Clinical and laboratory manifestations include fever, splenomegaly, neurologic dysfunction, coagulopathy, liver dysfunction, cytopenias, hypertriglyceridemia, hyperferritinemia, hemophagocytosis, and diminished NK cell activity. It is treated with immune suppressants, etoposide, and allogeneic hematopoietic stem cell transplantation; more than 50% of children who undergo transplant survive, but adults have quite poor outcomes even with aggressive management. Newer agents directed at subduing the uncontrolled immune response in a targeted fashion offer promise in this highly morbid disease.

Proliferation through activation: hemophagocytic lymphohistiocytosis in hematologic malignancy

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of cytokine-driven immune activation. Cardinal features include fever, hemophagocytosis, hepatosplenomegaly, lymphocytic infiltration, and hypercytokinemia that result in multisystem organ dysfunction and failure. Familial HLH is genetically driven, whereas secondary HLH (SHL) is caused by drugs, autoimmune disease, infection, or cancer. SHL is associated with worse outcomes, with a median overall survival typically of less than 1 year. This reflects difficulty in both diagnostic accuracy and in establishing reliable treatments, especially in cases of malignancy-induced SHL, which have significantly worse outcomes. Malignancy-induced HLH is seen almost exclusively with hematologic malignancies, constituting 97% of cases in the literature over the past 2 years. In these situations, the native immune response driven by CD8 T cells produces an overabundance of T helper 1 cytokines, notably interferon-γ, tumor necrosis factor-α, and interleukin-6, which establish a positive feedback loop of inflammation, enhancing replication of hematologic malignancies while leaving the host immune system in disarray. In this paper, we present 2 case studies of secondary HLH driven by HM, followed by a review of the literature discussing the cytokines driving HLH, diagnostic criteria, and current treatments used or undergoing investigation.

Mindfulness and its efficacy for psychological and biological responses in women with breast cancer

Many breast cancer survivors have to deal with a variety of psychological and physiological sequelae including impaired immune responses. The primary purpose of this randomized controlled trial was to determine the efficacy of a mindfulness‐based stress reduction (MBSR) intervention for mood disorders in women with breast cancer. Secondary outcomes were symptom experience, health status, coping capacity, mindfulness, posttraumatic growth, and immune status. This RTC assigned 166 women with breast cancer to one of three groups: MBSR (8 weekly group sessions of MBSR), active controls (self‐instructing MBSR) and non‐MBSR. The primary outcome measure was the Hospital Anxiety and Depression Scale. Secondary outcome measures were: Memorial Symptom Assessment Scale, SF‐36, Sense of Coherence, Five Facets of Mindfulness Questionnaire, and Posttraumatic Growth Index. Blood samples were analyzed using flow cytometry for NK‐cell activity (FANKIA) and lymphocyte phenotyping; concentrations of cytokines were determined in sera using commercial high sensitivity IL‐6 and IL‐8 ELISA (enzyme‐linked immunosorbent assay) kits. Results provide evidence for beneficial effects of MBSR on psychological and biological responses. Women in the MBSR group experienced significant improvements in depression scores, with a mean pre‐MBSR HAD‐score of 4.3 and post‐MBSR score of 3.3 (P = 0.001), and compared to non‐MBSR (P = 0.015). Significant improvements on scores for distress, symptom burden, and mental health were also observed. Furthermore, MBSR facilitated coping capacity as well as mindfulness and posttraumatic growth. Significant benefits in immune response within the MBSR group and between groups were observed. MBSR have potential for alleviating depression, symptom experience, and for enhancing coping capacity, mindfulness and posttraumatic growth, which may improve breast cancer survivorship. MBSR also led to beneficial effect on immune function; the clinical implications of this finding merit further research.

Application of an improved flow cytometry-based NK cell activity assay in adult hemophagocytic lymphohistiocytosis

Low or absent natural killer (NK) cell activity is included as one of the HLH-2004 diagnostic criteria. To improve the diagnosis of HLH, we aimed to establish a rapid and reliable NK cell activity assay that avoids the use of radioactivity. The K562 cell line, as standard NK target cells, was engineered to stably express enhanced green fluorescent protein (EGFP), which can be quantified by flow cytometry. The EGFP-flow cytometry method for measuring NK cell activity was improved by double staining of early and late apoptotic target cells. Whole-blood samples from healthy volunteers were assessed with this method, which demonstrated that optimal conditions were effector-target ratio of 10:1 and incubation time of 4 h. This method was further evaluated for samples from 113 HLH patients and 64 healthy volunteers. Mean NK cell activity in either primary or secondary HLH patients was significantly lower (P < 0.001) than in healthy individuals (20.23 ± 4.12%). Furthermore, primary HLH patients (10.76 ± 2.54%) exhibited even lower (P < 0.001) NK cell activity compared with secondary HLH patients (15.01 ± 3.62%). We have optimized and implemented this method in clinically relevant samples.

Clinical significance of lymphocyte subset changes in hemophagocytic lymphohistiocytosis of children

In order to examine the role of peripheral blood lymphocyte subsets on the diagnosis, treatment and prognosis of hemophagocytic lymphohistiocytosis (HLH), 30 affected children during the acute period of the disease and 30 healthy children within the same age range were selected to test their peripheral blood lymphocyte subsets using flow cytometry and compare these subsets. At the same time, the peripheral blood lymphocyte subsets of 20 children with complete remission from HLH were compared to those of 10 cases who succumbed to the disease. The proportion of CD3⁺ and CD8⁺ T cells were increased in children during the acute period. Additionally, the proportion of CD4⁺ T and CD3⁻CDl6⁺CD56⁺ natural killer (NK) cells and the ratio of CD4⁺/CD8⁺ cells were decreased in the same group of children, with the differences being statistical significance (P<0.05). The proportion of CD19⁺ B cells showed no differences in the affected and healthy groups. HLH children during the remission period had a higher proportion of CD3⁺ and CD8⁺ T cells than that in the control group, but the ratio of CD4⁺ T and CD4⁺/CD8⁺ were lower than that in the control group, with the differences being statistically significant (P<0.05). The proportion of CD19⁺ B cells and CD3⁻CD16⁺CD56⁺ NK cells revealed no significant difference between the two groups. In addition, regarding the proportion of CD3⁺, CD4⁺, CD8⁺ T, CD19⁺ B cells, CD3⁻CDl6⁺CD56⁺ NK cells and the ratio of CD4⁺/CD8⁺, and there were no significant differences. The results showed that HLH modifies the peripheral blood lymphocyte subsets and causes cellular immunity disorders. Thus, monitoring these dynamic changes can be useful in the diagnosis of HLH and evaluate the response to therapy.

Establishing the reference intervals of NK cell functions in healthy adults

Natural killer (NK) cells play a key role in host defense against microbial pathogens. Establishing the reference intervals (RIs) of NK cell functions would be valuable in assessing the immune status of hosts. We evaluated the NK cell activity in healthy adults. We further established and validated the RIs of representative NK cell functions. Flow cytometry was used to evaluate the cytokine production and CD107a degranulation of NK cells. Levels of soluble IFN-γ in the culture supernatants were evaluated by ELISA. Our results demonstrated that the intracellular IFN-γ production of NK cells was positively correlated with CD107a expression and soluble IFN-γ levels. There were no significant differences in NK cell functions between different age and gender groups. The mean values and RIs of representative NK cell functions are as following: IFN-γ(+) NK cells (%): 28.09 (11.3-51.95); CD107a(+) NK cells (%): 17.90 (9.852-27.56); soluble IFN-γ (pg/ml): 330.4 (41.38-717.8). In addition, the intracellular IFN-γ production and degranulation activity of NK cells in patients with colorectal cancer were significantly lower than that in healthy adults. Our study has established the RIs of NK cell functions in healthy adults, which might be used for monitoring the immune status of the hosts.

Hemophagocytic Lymphohistiocytosis in Adults

Hemophagocytic lymphohistiocytosis (HLH) is a rare but potentially fatal syndrome of pathologic immune dysregulation characterized by clinical signs and symptoms of extreme inflammation. HLH can occur as a genetic or sporadic disorder and, though seen as an inherited condition affecting primarily a pediatric population, can occur at any age and can be encountered in association with a variety of underlying diseases. Clinically the syndrome, whether genetic or acquired, is characterized by fever, hepatosplenomegaly, cytopenias, and activated macrophages in hematopoietic organs. Therapy centers on suppression of this hyperinflammatory state with cytotoxic, immunosuppressive therapy and treatment of any existing HLH triggers.

Spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis (FHL) patients in India

BACKGROUND

Inherited perforin deficiency is a rare autosomal recessive disorder that causes severe form of hemophagocytic lymphohistiocytosis (FHL2). The main aim of this study was to analyze the nature of gene mutations in a cohort of Indian patients with FHL2 and to utilize this knowledge for genetic counseling and prenatal diagnosis.

METHODS

13 HLH patients with abnormal perforin expression on NK cells by flow cytometry were included in the study. The entire coding region and intronic splice sites of the PRF1 gene were sequenced from the genomic DNA of these patients.

RESULTS

10 patients from the present series had an early presentation with severe clinical manifestations, while 3 had a delayed onset with unusual presenting features viz Hodgkin's lymphoma, tuberculosis and acute lymphoblastic leukemia. Sequence analysis revealed 11 different mutations (8 novel and 3 previously reported) spread over the entire coding region of PRF1 gene. Missense mutation Trp129Ser in heterozygous state was present in all the 3 patients with a delayed onset of the disease.

CONCLUSION

A wide heterogeneity was observed in the nature of mutations in Indian FHL2 patients. Molecular characterization of PRF1 gene was not only used in the confirmation of diagnosis but also in genetic counseling and pre-natal diagnosis in affected families.

Adult haemophagocytic syndrome

Haemophagocytic syndromes (haemophagocytic lymphohistiocytosis) have a wide range of causes, symptoms, and outcomes, but all lead to a hyperinflammatory response and organ damage--mainly reported in paediatric patients, but reports of adult presentation are increasing. Analysis of the genetic and molecular pathophysiology of these syndromes have improved the understanding of the crosstalk between lymphocytes and histiocytes and their regulatoty mechanisms. Clinical presentations with a broad differential diagnosis, and often life-threatening outcome, complicate the management, which might include supportive intensive care, immunosuppressive and biological treatments, or haemopoietic stem cell transplantation. Insufficient knowledge of these syndromes could contribute to poor prognosis. Early diagnosis is essential to initiate appropriate treatment and improve the quality of life and survival of patients with this challenging disorder.

Killer cell immunoglobulin-like receptor gene polymorphisms predispose susceptibility to Epstein-Barr virus associated hemophagocytic lymphohistiocytosis in Chinese children

Epstein-Barr virus associated hemophagocytic lymphohistiocytosis (EBV-HLH) has a high mortality rate among children. The pathogenesis of, and underlying predisposing factors for, EBV-HLH are as yet unclear; however, natural killer cells may play a key role in progression of the disease. This study attempted to determine whether killer cell immunoglobulin-like receptor (KIR) gene polymorphisms are responsible for susceptibility to EBV-HLH. Of the 125 children with EBV infection studied, 59 had EBV-HLH and 66 patients had EBV associated infectious mononucleosis (IM) without HLH. The control group was 146 normal children without immune deficiency. KIR polymorphisms were determined by polymerase chain reaction with sequence-specific primers. KIR polymorphism data were analyzed using the X(2) test or Fisher's exact test. The overall observed carrier frequency (OF) of KIR2DS5 was significantly higher in EBV-HLH patients than in IM patients and normal controls (49.2% versus 31.8%, P = 0.048; 49.2% versus 31.5%, P = 0.018, respectively), and the odds ratios (95% confidence interval) were 2.071 (1.001-4.286) and 2.101(1.132-3.900) respectively. The OF of KIR3DS1 was significantly higher in the EBV-HLH patients than in the IM patients (47.4% versus 24.6%, P = 0.012), but not different from normal controls. In summary, KIR polymorphisms may be involved in the development of EBV-HLH, with KIR2DS5 promoting susceptibility to this disease. The obtained KIR data will enrich the understanding of genetic relationships among diseases associated with EBV infection in children.