Key diagnostic markers for autoimmune lymphoproliferative syndrome with molecular genetic diagnosis.

Autoimmune lymphoproliferative syndrome (ALPS) is a rare immunodeficiency caused by mutations in genes affecting the extrinsic apoptotic pathway (FAS, FASL, CASP10). This study evaluated the clinical manifestations, laboratory findings, and molecular genetic results of 215 patients referred as possibly having ALPS. Double-negative T-cell (DNT) percentage and in vitro apoptosis functional tests were evaluated by fluorescence-activated cell sorting; interleukin 10 (IL-10) and IL-18 and soluble FAS ligand (sFASL) were measured by enzyme-linked immunosorbent assay. Genetic analysis was performed by next-generation sequencing. Clinical background data were collected from patients' records. Patients were categorized into definite, suspected, or unlikely ALPS groups, and laboratory parameters were compared among these groups. Of 215 patients, 38 met the criteria for definite ALPS and 17 for suspected ALPS. The definite and suspected ALPS patient populations showed higher DNT percentages than unlikely ALPS and had higher rates of lymphoproliferation. Definite ALPS patients had a significantly more abnormal in vitro apoptosis function, with lower annexin, than patients with suspected ALPS (P = .002) and patients not meeting ALPS criteria (P < .001). The combination of elevated DNTs and an abnormal in vitro apoptosis functional test was the most useful in identifying all types of ALPS patients; the combination of an abnormal in vitro apoptosis functional test and elevated sFASLs was a predictive marker for ALPS-FAS group identification. Lymphoproliferation, apoptosis functional test, and DNTs are the most sensitive markers; elevated IL-10 and IL-18 are additional indicators for ALPS. The combination of elevated sFASLs and abnormal apoptosis function was the most valuable prognosticator for patients with FAS mutations.

Autoimmune Lymphoproliferative Syndrome: An Overview.

Autoimmune lymphoproliferative syndrome (ALPS) is an inherited nonmalignant lymphoproliferative disorder characterized by heterozygous mutations within the first apoptosis signal receptor (FAS) signaling pathway. Defects in FAS-mediated apoptosis cause an expansion and accumulation of autoreactive CD4- and CD8- (double-negative) T cells, leading to cytopenias, splenomegaly, lymphadenopathy, autoimmune disorders, and a greatly increased lifetime risk of lymphoma. The differential diagnosis of ALPS includes infection, other inherited immunodeficiency disorders, primary and secondary autoimmune syndromes, and lymphoma. The most consistent pathologic feature is a florid paracortical expansion of double-negative T cells in lymph nodes. A presumptive clinical diagnosis can be made from symptoms and a constellation of laboratory test results. However, a definitive diagnosis requires ancillary testing and enables disease subclassification. Recognition of ALPS is critical, as treatment with immunosuppressive therapies can effectively reduce or ameliorate symptoms for most patients.

18F-FDG PET Imaging Features of Patients With Autoimmune Lymphoproliferative Syndrome.

INTRODUCTION: Autoimmune lymphoproliferative syndrome (ALPS) is a rare immune dysregulatory condition, usually presenting in childhood with massive lymphadenopathy, splenomegaly, and an increased incidence of lymphoma. Methods to differentiate between benign ALPS adenopathy and lymphoma are needed. To this end, we evaluated the usefulness of FDG PET. METHODS: We prospectively evaluated 76 ALPS/ALPS-like patients including FS-7-associated surface antigen (FAS) germline mutation with (n = 4) and without lymphoma (n = 50), FAS-somatic (n = 6), ALPS-unknown (n = 6), and others (n = 10) who underwent FDG PET. Uptakes in 14 nodal sites, liver, and spleen were determined. RESULTS: In 76 ALPS patients, FDG PET showed uptake in multiple nodal sites in all but 1 patient. The highest SUVmax values in FAS mutation without lymphoma, FAS mutation with lymphoma, FAS somatic, ALPS-unknown, and other genetic mutations were a median (range) 9.2 (4.3-25), 16.2 (10.7-37.2), 7.6 (4.6-18.1), 11.5 (4.8-17.2), and 5.5 (0-15.3), respectively. Differences between uptake in the FAS group with and without lymphoma were statistically significant, but overlapped, making discrimination between individuals with/without lymphoma impossible. The spleen:liver uptake ratio was greater than 1 in 82% of patients. CONCLUSIONS: While statistically significant differences were observed in FAS mutation ALPS with and without lymphoma, the significant overlap in FDG uptake and visual appearance in many patients prevents discrimination between patients with and without lymphoma. Similar patterns of FDG biodistribution were noted between the various ALPS subgroups.

The Autoimmune Lymphoproliferative Syndrome with Defective FAS or FAS-Ligand Functions.

The autoimmune lymphoproliferative syndrome (ALPS) is a non-malignant and non-infectious uncontrolled proliferation of lymphocytes accompanied by autoimmune cytopenia. The genetic etiology of the ALPS was described in 1995 by the discovery of the FAS gene mutations. The related apoptosis defect accounts for the accumulation of autoreactive lymphocytes as well as for specific clinical and biological features that distinguish the ALPS-FAS from other monogenic defects of this apoptosis pathway, such as FADD and CASPASE 8 deficiencies. The ALPS-FAS was the first description of a monogenic cause of autoimmunity, but its non-Mendelian expression remained elusive until the description of somatic and germline mutations in ALPS patients. The recognition of these genetic diseases brought new information on the role of this apoptotic pathway in controlling the adaptive immune response in humans.

Autoimmune Lymphoproliferative Syndrome-FAS Patients Have an Abnormal Regulatory T Cell (Treg) Phenotype but Display Normal Natural Treg-Suppressive Function on T Cell Proliferation.

Objective: Autoimmune lymphoproliferative syndrome (ALPS) with FAS mutation (ALPS-FAS) is a nonmalignant, noninfectious, lymphoproliferative disease with autoimmunity. Given the central role of natural regulatory T cells (nTregs) in the control of lymphoproliferation and autoimmunity, we assessed nTreg-suppressive function in 16 patients with ALPS-FAS. Results: The proportion of CD25highCD127low Tregs was lower in ALPS-FAS patients than in healthy controls. This subset was correlated with a reduced CD25 expression in CD3+CD4+ T cells from ALPS patients and thus an abnormally low proportion of CD25highFOXP3+ Helios+ T cells. The ALPS patients also displayed a high proportion of naïve Treg (FOXP3lowCD45RA+) and an unusual subpopulation (CD4+CD127lowCD15s+CD45RA+). Despite this abnormal phenotype, the CD25highCD127low Tregs' suppressive function was unaffected. Furthermore, conventional T cells from FAS-mutated patients showed normal levels of sensitivity to Treg suppression. Conclusion: An abnormal Treg phenotype is observed in circulating lymphocytes of ALPS patients. However, these Tregs displayed a normal suppressive function on T effector proliferation in vitro. This is suggesting that lymphoproliferation observed in ALPS patients does not result from Tregs functional defect or T effector cells insensitivity to Tregs suppression.

eRepo-ORP: Exploring the Opportunity Space to Combat Orphan Diseases with Existing Drugs.

About 7000 rare, or orphan, diseases affect more than 350 million people worldwide. Although these conditions collectively pose significant health care problems, drug companies seldom develop drugs for orphan diseases due to extremely limited individual markets. Consequently, developing new treatments for often life-threatening orphan diseases is primarily contingent on financial incentives from governments, special research grants, and private philanthropy. Computer-aided drug repositioning is a cheaper and faster alternative to traditional drug discovery offering a promising venue for orphan drug research. Here, we present eRepo-ORP, a comprehensive resource constructed by a large-scale repositioning of existing drugs to orphan diseases with a collection of structural bioinformatics tools, including eThread, eFindSite, and eMatchSite. Specifically, a systematic exploration of 320,856 possible links between known drugs in DrugBank and orphan proteins obtained from Orphanet reveals as many as 18,145 candidates for repurposing. In order to illustrate how potential therapeutics for rare diseases can be identified with eRepo-ORP, we discuss the repositioning of a kinase inhibitor for Ras-associated autoimmune leukoproliferative disease. The eRepo-ORP data set is available through the Open Science Framework at https://osf.io/qdjup/.

TCF1 deficiency ameliorates autoimmune lymphoproliferative syndrome (ALPS)-like phenotypes of lpr/lpr mice.

Autoimmune lymphoproliferative syndrome (ALPS) is an incurable disease, which is characterized by non-malignant autoimmune lymphoproliferation. TCF1 is a key effector in the canonical Wnt/ß-catenin pathway, regulating the development, activation and function of T cells. In this study, we aimed to explore the potential role of TCF1 in the development of ALPS-like phenotypes of lpr/lpr mice. We acquired TCF1-/- lpr/lpr double mutant mice by crossing TCF1 deficiency mice with lpr/lpr mice. Splenocyte compositions, serum cytokines levels, antidsDNA antibody production and kidney pathology were examined in the TCF1-/- lpr/lpr mice. With these examinations, we revealed that TCF1 deficiency relieved most manifestations of ALPS-like phenotype, which were caused by Fas mutation in TCF1-/- lpr/lpr mice. Splenocyte total numbers and compositions were downregulated to the similar levels with wildtype mice. TE and TEM cells were decreased in TCF1-/- lpr/lpr compared with lpr/lpr mice. The levels of autoantibodies and proinflammatory factors in serum, and the histopathology changes and the relative mRNA levels of proinflammatory factors in kidney all displayed parallel tendency in TCF1-/- lpr/lpr mice. Our study demonstrated that TCF1 deficiency ameliorated the ALPS-like phenotypes of TCF1-/- lpr/lpr mice, which might indicate a potential therapeutic direction for ALPS.

Bone marrow findings in autoimmune lymphoproliferative syndrome with germline FAS mutation.

Autoimmune lymphoproliferative syndrome is a rare genetic disorder characterized by defective FAS-mediated apoptosis, autoimmune disease, accumulation of mature T-cell receptor alpha/beta positive, CD4 and CD8 double-negative T cells and increased risk of lymphoma. Despite frequent hematologic abnormalities, literature is scarce regarding the bone marrow pathology in autoimmune lymphoproliferative syndrome. We retrospectively reviewed 3l bone marrow biopsies from a cohort of 240 patients with germline FAS mutations. All biopsies were performed for the evaluation of cytopenias or to rule out lymphoma. Clinical information was collected and morphological, immunohistochemical, flow cytometric and molecular studies were performed. Bone marrow lymphocytosis was the predominant feature, present in 74% (23/31) of biopsies. The lymphoid cells showed several different patterns of infiltration, most often forming aggregates comprising T cells in 15 cases, B cells in one and a mixture of T and B cells in the other seven cases. Double-negative T cells were detected by immunohistochemistry in the minority of cases (10/31; 32%); significantly, all but one of these cases had prominent double-negative T-lymphoid aggregates, which in four cases diffusely replaced the marrow space. One case showed features of Rosai-Dorfman disease, containing scattered S-100+ cells with emperipolesis and double-negative T cells. No clonal B or T cells were detected by polymerase chain reaction in any evaluated cases. Classical Hodgkin lymphoma was identified in three cases. Our results demonstrate that infiltrates of T cells, or rarely B cells, can be extensive in patients with autoimmune lymphoproliferative syndrome, mimicking lymphoma. A multi-modality approach, integrating clinical, histological, immunohistochemical as well as other ancillary tests, can help avoid this diagnostic pitfall. This study is registered at Clinicaltrials.gov ID # NCT00001350.

Updated Understanding of Autoimmune Lymphoproliferative Syndrome (ALPS).

Autoimmune lymphoproliferative syndrome (ALPS), a disorder characterized by immune dysregulation due to disrupted lymphocyte homeostasis, is mainly resulted from the mutations in FAS-mediated apoptotic pathway. In addition, other mutations of the genes such as Fas-ligand (FASLG), Caspase 10 (CASP10) and Caspase 8 (CASP8), NRAS and KRAS have also been observed in a small number of patients with ALPS or ALPS-related disorders. However, approximately 20-30% of patients with ALPS have unidentified defect. Its clinical manifestations observed in multiple family members include unexplained lymphadenopathy, hepatosplenomegaly, autoimmune cytopenias such as thrombocytopenia, neutropenia, and anemia due to excessive production of antibodies by lymphocytes, elevated number of double-negative T (DNT) cells, and increased risk of lymphoma. As a very rare disease, ALPS was first characterized in the early 1990s. More than 300 families with hereditary ALPS have been reported till now; nearly 500 patients from these families have been studied and followed worldwide over the last 20 years. ALPS has historically considered as a primary immune defect presenting in early childhood, however, recent studies have shown that it may be more common than previous thought because adult onset presentation is increasingly becoming recognized and more adult ALPS patients are diagnosed. The new genetic and biological insights have improved the understanding of ALPS and a number of targeted therapeutic strategies such as mycophenolate mofetil, sirolimus, and pentostatin have been successfully applied in ALPS patients with promising treatment efficacy. This article comprehensively reviews the clinical and laboratory manifestations, new research advances in the molecular pathogenesis, diagnosis and treatments of this disorder.

A novel homozygous Fas ligand mutation leads to early protein truncation, abrogation of death receptor and reverse signaling and a severe form of the autoimmune lymphoproliferative syndrome.

We report a novel type of mutation in the death ligand FasL that was associated with a severe phenotype of the autoimmune lymphoproliferative syndrome in two patients. A frameshift mutation in the intracellular domain led to complete loss of FasL expression. Cell death signaling via its receptor and reverse signaling via its intracellular domain were completely abrogated. In vitro lymphocyte proliferation induced by weak T cell receptor stimulation could be blocked and cell death was induced by engagement of FasL in T cells derived from healthy individuals and a heterozygous carrier, but not in FasL-deficient patient derived cells. Expression of genes implicated in lymphocyte proliferation and activation (CCND1, NFATc1, NF-κB1) was increased in FasL-deficient T cells and could not be downregulated by FasL engagement as in healthy cells. Our data thus suggest, that deficiency in FasL reverse signaling may contribute to the clinical lymphoproliferative phenotype of ALPS.

Investigation of common variable immunodeficiency patients and healthy individuals using autoimmune lymphoproliferative syndrome biomarkers.

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of dysregulated lymphocyte homeostasis. Biomarkers including elevated CD3+TCRαß+CD4-CD8- double negative T cells (TCRαß+ DNT), IL-10, sCD95L and vitamin B12 can be used to differentiate between ALPS and common variable immunodeficiency (CVID) patients with an overlapping clinical phenotype. We investigated the utility of ALPS biomarkers in 13 CVID patients with lymphoproliferation and/or autoimmune cytopaenia with comparison to 33 healthy controls. Vitamin B12 (P < 0.01) and IL-10 (P < 0.0001), but not sCD95L or TCRαß+ DNT, were increased in CVID compared to controls. The 95th percentile for TCRαß+ DNT in healthy controls was used to define a normal range up to 2.3% of total lymphocytes or 3.4% of T cells. These frequencies lie markedly beyond the cut offs used in current ALPS diagnostic criteria (≥ 1.5% of total lymphocytes or 2.5% of CD3+ lymphocytes), suggesting these limits may have poor specificity for ALPS.

Forced miR-146a expression causes autoimmune lymphoproliferative syndrome in mice via downregulation of Fas in germinal center B cells.

By inhibiting target gene expression, microRNAs (miRNAs) play major roles in various physiological and pathological processes. miR-146a, a miRNA induced upon lipopolysaccharide (LPS) stimulation and virus infection, is also highly expressed in patients with immune disorders such as rheumatoid arthritis, Sjögren's syndrome, and psoriasis. Whether the high level of miR-146a contributes to any of these pathogenesis-related processes remains unknown. To elucidate the function of miR-146a in vivo, we generated a transgenic (TG) mouse line overexpressing miR-146a. Starting at an early age, these TG mice developed spontaneous immune disorders that mimicked human autoimmune lymphoproliferative syndrome (ALPS) with distinct manifestations, including enlarged spleens and lymph nodes, inflammatory infiltration in the livers and lungs, increased levels of double-negative T cells in peripheral blood, and increased serum immunoglobulin G levels. Moreover, with the adoptive transfer approach, we found that the B-cell population was the major etiological factor and that the expression of Fas, a direct target of miR-146a, was significantly dampened in TG germinal center B cells. These results indicate that miR-146a may be involved in the pathogenesis of ALPS by targeting Fas and may therefore serve as a novel therapeutic target.

Disease causing mutations in the TNF and TNFR superfamilies: Focus on molecular mechanisms driving disease.

The tumor necrosis factor (TNF) and TNF receptor (TNFR) superfamilies comprise multidomain proteins with diverse roles in cell activation, proliferation and cell death. These proteins play pivotal roles in the initiation, maintenance and termination of immune responses and have vital roles outside the immune system. The discovery and analysis of diseases associated with mutations in these families has revealed crucial mechanistic details of their normal functions. This review focuses on mutations causing four different diseases, which represent distinct pathological mechanisms that can exist within these superfamilies: autoimmune lymphoproliferative syndrome (ALPS; FAS mutations), common variable immunodeficiency (CVID; TACI mutations), tumor necrosis factor receptor associated periodic syndrome (TRAPS; TNFR1 mutations) and hypohidrotic ectodermal dysplasia (HED; EDA1/EDAR mutations). In particular, we highlight how mutations have revealed information about normal receptor-ligand function and how such studies might direct new therapeutic approaches.

Autoimmune lymphoproliferative syndrome mimicking chronic active Epstein-Barr virus infection.

Chronic active Epstein-Barr virus infection (CAEBV) is defined as a systemic EBV-associated lymphoproliferative disease characterized by fever, lymphadenopathy, and splenomegaly in apparently immunocompetent persons. Recent studies have revealed that EBV infects T or natural killer cells in most patients with CAEBV; the etiology of CAEBV, however, remains unknown. Autoimmune lymphoproliferative disorder (ALPS) is an inherited disorder associated with defects in apoptosis, and clinically characterized by lymphadenopathy, splenomegaly, hypergammaglobulinemia, and autoimmune disease. ALPS is most often associated with mutations in the FAS gene, which is an apoptosis-signaling receptor important for homeostasis of the immune system. Based on the clinical similarity between ALPS and CAEBV with respect to lymphoproliferation, we have examined the possibility of the co-occurrence of ALPS in patients with a diagnosis of CAEBV. In this study, we have identified FAS gene mutations in three Japanese patients with lymphadenopathy, hepatosplenomegaly, and unusual EBV infection, who were diagnosed with CAEBV. These observations, which indicate that the clinical development of ALPS may be associated with EBV infection, alert us to a potential diagnostic pitfall of CAEBV.

The importance of LAT in the activation, homeostasis, and regulatory function of T cells.

LAT (linker for activation of T cells) is a transmembrane adaptor protein that plays an essential role in TCR-mediated signaling and thymocyte development. Because LAT-deficient mice have an early block in thymocyte development, we utilized an inducible system to delete LAT in primary T cells to study LAT function in T cell activation, homeostasis, and survival. Deletion of LAT caused primary T cells to become unresponsive to stimulation from the TCR and impaired T cell homeostatic proliferation and long term survival. Furthermore, deletion of LAT led to reduced expression of Foxp3, CTLA-4, and CD25 in T(reg) cells and impaired their function. Consequently, mice with LAT deleted developed a lymphoproliferative syndrome similar to that in LATY136F mice, although less severe. Our data implicate that LAT has positive and negative roles in the regulation of mature T cells.