Lymphocytic vasculitis in X-linked lymphoproliferative disease

Systemic vasculitis is an uncommon manifestation of X-linkedlymphoproliferative disease (XLP), a disorder in which there is aselective immune deficiency to Epstein-Barr virus (EBV). The molecularbasis for XLP has recently been ascribed to mutations withinSLAM-associated protein (SAP), an SH2 domain-containing proteinexpressed primarily in T cells. The authors describe a patient who diedas a result of chronic systemic vasculitis and fulfilled clinicalcriteria for the diagnosis of XLP. Sequencing of this patient'sSAP gene uncovered a novel point mutation affecting the SH2domain. The patient presented with virus-associated hemophagocytic syndrome (VAHS) and later had chorioretinitis, bronchiectasis, andhypogammaglobulinemia develop. He further developed mononeuritis andfatal respiratory failure. Evidence of widespread small and mediumvessel vasculitis was noted at autopsy with involvement of retinal,cerebral, and coronary arteries as well as the segmental vessels of thekidneys, testes, and pancreas. Immunohistochemical analysis usingantibodies to CD20, CD45RO, and CD8 revealed that the vessel wallinfiltrates consisted primarily of CD8⁺ T cells,implying a cytotoxic T-lymphocyte response to antigen. EBV DNA wasdetected by polymerase chain reaction (PCR) in arterial wall tissuemicrodissected from infiltrated vessels further suggesting that theCD8⁺ T cells were targeting EBV antigens within theendothelium. The authors propose that functional inactivation of theSAP protein can impair the immunologic response to EBV, resulting insystemic vasculitis.     

Detection of X-linked lymphoproliferative disease using molecular and immunovirologic markers

PURPOSE, PATIENTS, AND METHODS: Detection of males affected with the X-linked lymphoproliferative disease (XLP) was sought using immunovirologic and molecular genetic linkage techniques. The study population consisted of 20 males in six families with XLP. RESULTS: Concordance for detection of affected males was 100% when linkage analysis using DXS42 and DXS37 DNA probes and antibody responses to challenge with bacteriophage phi X174 were both determined. Most affected males showing IgG subclass immune deficiency could not produce antibodies to Epstein-Barr virus nuclear antigen and had deficient responses to challenge with bacteriophage phi X174. CONCLUSION: Use of only one of the techniques described can fail to lead to the diagnosis of XLP, because problems can prevail with each individual determination.     

SAP mediates specific cytotoxic T-cell functions in X-linked lymphoproliferative disease

Cytotoxic T cells (CTLs) and natural killer cells play a major role in the immune response to Epstein-Barr virus (EBV) infection. In X-linked lymphoproliferative (XLP) disease, a severe immunodeficiency, immunodysregulatory phenomena are observed following EBV infection, suggesting that defects exist in these effector populations. The gene defective in XLP is SAP (signaling lymphocytic activation molecule [SLAM]-associated protein), an adaptor protein that mediates signals through SLAM and other immunoglobulin superfamily receptors including 2B4. We generated EBV-specific T-cell lines from controls and XLP patients and examined CTL function in response to different stimuli. We show that XLP patients can generate EBV-T-cell lines that are phenotypically similar to those from controls. XLP patient EBV-T-cell lines showed a significant decrease in interferon-gamma (IFN-gamma) production in response to 2B4 and autologous EBV-transformed lymphoblastoid cell line (LCL) stimulation but not in response to SLAM. Furthermore, XLP EBV-T-cell lines demonstrated markedly decreased cytotoxic activity against autologous LCLs. By retroviral gene transfer of the SAP gene into XLP EBV-T-cell lines, we show reconstitution of IFN-gamma production and of cytotoxic activity confirming SAP-dependent defects. These studies demonstrate that in XLP the lack of SAP affects specific signaling pathways resulting in severe disruption of CTL function.     

The proapoptotic function of SAP provides a clue to the clinical picture of X-linked lymphoproliferative disease

Deletion or mutation of the SAP gene is associated with the X-linked lymphoproliferative disease (XLP) that is characterized by extreme sensitivity to Epstein-Barr virus (EBV). Primary infection of the affected individuals leads to serious, sometimes fatal infectious mononucleosis (IM) and proneness to lymphoma. Our present results revealed a proapoptotic function of SAP by which it contributes to the maintenance of T-cell homeostasis and to the elimination of potentially dangerous DNA-damaged cells. Therefore, the loss of this function could be responsible for the uncontrolled T-cell proliferation in fatal IM and for the generation of lymphomas. We show now the role of SAP in apoptosis in T and B lymphocyte-derived lines. Among the clones of T-ALL line, the ones with higher SAP levels succumbed more promptly to activation induced cell death (AICD). Importantly, introduction of SAP expression into lymphoblastoid cell lines (LCL) established from XLP patients led to elevated apoptotic response to DNA damage. Similar results were obtained in the osteosarcoma line, Saos-2. We have shown that the anti-apoptotic protein VCP (valosin-containing protein) binds to SAP, suggesting that it could be instrumental in the enhanced apoptotic response modulated by SAP.     

Lentiviral-vector-mediated gene therapy for X-linked lymphoproliferative disease restores humoral and cellular functions

BackgroundX-linked lymphoproliferative disease (XLP) arises from mutations in the gene encoding SAP, an intracellular adaptor protein expressed in T cells, natural killer (NK) cells, and natural killer T (NKT) cells. SAP deficiency causes abnormalities of NK cell cytotoxicity, NKT cell development, and T-cell-dependent humoral function. Clinical manifestations are characterised by haemophagocytic lymphohistiocytosis (HLH), lymphoma, and dysgammaglobulinaemia. Curative treatment is limited to allogeneic haemopoietic stem-cell transplantion (HSCT). Somatic gene therapy offers a potential cure in XLP. We have developed a lentiviral mediated gene therapy strategy to correct immune defects in XLP.MethodsWe designed a lentiviral vector incorporating codon-optimised human SAP cDNA and green fluorescent protein (GFP) driven by the elongation factor-1 short (EFS) promoter. Haemopoietic stem-cell progenitors from SAP-deficient mice were transduced with SAP-GFP (n=10) or GFP only (n=9) vectors before transplantation into irradiated SAP-deficient recipients. Animals were sacrificed 3 months later, 10 days post vaccination with NP-CGG to assess functional humoral reconstitution.FindingsBoth SAP and GFP expression was evident in bone marrow, thymus, spleen, and peripheral blood cells. NK cell cytotoxicity was restored to wild type levels in mice receiving the SAP-GFP vector, and NKT cell development was seen in SAP-GFP transduced mice at levels significantly higher than those seen in SAP-deficient or control mice. Baseline IgG, IgM, IgG1, and IgG3 levels were significantly increased and T-cell-dependent humoral responses were also restored, with SAP-GFP transduced mice having levels of NP-specific immunoglobulin that were significantly higher than SAP-deficient mice or controls.InterpretationWe demonstrate correction of cellular and humoral defects in SAP-deficient mice through lentiviral-vector-mediated gene transfer into haemopoietic progenitor cells, providing proof of concept for gene therapy in XLP.FundingWellcome Trust and Leukaemia Lymphoma Research.     

X-linked lymphoproliferative syndrome: a genetic condition typified by the triad of infection, immunodeficiency and lymphoma

X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by the clinical triad of increased susceptibility to primary Epstein-Barr virus (EBV) infection, dysgammaglobulinaemia and lymphoma. Most cases are caused by germline mutations in the SH2D1A gene, which encodes the adaptor molecule Signalling Lymphocytic Activation Molecule (SLAM)-associated protein (SAP). Recently, a subset of patients with an XLP-like phenotype was found to carry mutations in XIAP, the gene encoding the X-linked inhibitor of apoptosis protein (XIAP). Studies of XLP patients and Sap-/- mice reveal that loss of SAP expression impairs immune cell activities, such as natural killer and CD8+ T cell cytotoxicity, T cell cytokine production, activation-induced cell death, germinal centre formation and natural killer T cell development. Efforts to dissect the diverse roles of SAP and XIAP are enhancing our understanding of immune cell biology and defining how genetic defects in these molecules predispose to EBV-specific as well as more general cellular and humoral immune dysfunction. These studies are also highlighting critical signalling pathways that might be amenable to pharmacological targeting to improve the treatment of XLP and other disorders associated with impaired antiviral and antitumour immunity.     

Mapping the X-linked lymphoproliferative syndrome.

The X-linked lymphoproliferative syndrome is triggered by Epstein-Barr virus infection and results in fatal mononucleosis, immunodeficiency, and lymphoproliferative disorders. This study shows that the mutation responsible for X-linked lymphoproliferative syndrome is genetically linked to a restriction fragment length polymorphism detected with the DXS42 probe (from Xq24-q27). The most likely recombination frequency between the loci is 4%, and the associated logarithm of the odds is 5.26. Haplotype analysis using flanking restriction fragment length polymorphism markers indicates that the locus for X-linked lymphoproliferative syndrome is distal to probe DXS42 but proximal to probe DXS99 (from Xq26-q27). It is now possible to predict which members of a family with X-linked lymphoproliferative syndrome are carrier females and to diagnose the syndrome prenatally.     

The biochemical and clinical consequences of 2'-deoxycoformycin in refractory lymphoproliferative malignancy

A deficiency of adenosine deaminase, an enzyme important in purine nucleoside catabolism, is associated with a severe combined immunodeficiency disease in children. Inhibition of this enzyme in vitro and in vivo results in an impairment in lymphoblast proliferation. We have investigated the pharmacologic inhibition of this enzyme by 2'-deoxycoformycin in 15 patients with hematologic malignancies. Biochemical consequences of the administration of this agent were closely monitored in erythrocytes, nucleated peripheral blood and bone marrow cells, serum, and urine. A marked rise in erythrocyte dATP was accompanied by a depletion of ATP in those patients exhibiting toxicity. Most patients excreted large amounts of deoxyadenosine but not adenosine in the urine. Serum deoxyadenosine rose in patients demonstrating a marked decrease in cell mass. The biochemical disturbances and clinical toxicity, including hepatic, renal, and conjunctival abnormalities, were usually reversible. Central nervous system toxicity, which potentially was the most serious consequence, was associated with high erythrocyte dATP/ATP ratios and high levels of cerebrospinal fluid deoxyadenosine. In patients with lymphoma and leukemia, objective responses were observed but were short- lived. Patients with chronic lymphocytic leukemia receiving weekly low doses of the drug demonstrated minimal toxicity and some efficacy. The chemotherapeutic potential o 2'-deoxycoformycin, as either a single agent or in combination with Ara-A, merits further exploration.     

Autoimmune lymphoproliferative syndrome: molecular basis of disease and clinical phenotype

Autoimmune lymphoproliferative syndrome (ALPS) is a variable clinical condition manifest by lymphoproliferative disease, autoimmune cytopenias and susceptibility to malignancy. Central to the cellular pathogenesis is defective FAS-induced apoptosis, which in turn leads to dysregulation of lymphocyte homeostasis. The majority of patients have heterozygous mutations in the FAS ( TNFRSF6 ) gene, but the condition is genetically heterogeneous and mutations in FAS ligand and caspase-8 and caspase-10, all of which are involved in Fas mediated signalling, have also been identified. This review provides a detailed insight into the pathophysiology of lymphocyte apoptosis and how this relates to the variable and complex clinical manifestations of ALPS.     

Chronic B-cell lymphoproliferative disease: relationship between immunophenotype and clinical stage

We analyzed the immunophenotype in 34 cases of B-CLD referred to our observation over a 13-month period. In 25 patients the classical phenotypic pattern of B-CLL was observed; in 9 cases clinical, morphocytochemical, and histologic findings were consistent with CLL but differed in phenotype. The results indicate that four immunophenotypic subgroups related to CD5 and FMC7 expression may be identified within B-CLL. Clinical correlations in these cases suggest that B-CLL with anomalous phenotypes are more frequently diagnosed at a later stage than classical B-CLL. Furthermore, while the percentage of CD3+ cells did not vary among the subgroups, a comparison of the CD4/CD8 ratio disclosed marked differences.     

Hematopathology and pathogenesis of the X-linked recessive lymphoproliferative syndrome

Subtle immunodeficiency to infectious agents including measles virus and the Epstein-Barr virus (EBV) has been described in the X-linked recessive lymphoproliferative syndrome. This syndrome has affected six male cousins and possibly another boy. Three brothers died of an infectious mononucleosis syndrome, in a maternal cousin agammaglobulinemia developed three years after infectious mononucleosis, and two half-brothers of the Duncan kindred died of lymphoma of the brain and intestinal tract, respectively. In three of the boys, unusual measles viral infections had developed. Paramyxovirus-like particles suggestive of measles virus were seen at necropsy in the atrophic lymphoid tissue of two boys. Also, numerous plasma cells were seen in the brains, visceral organs and the thymus glands, and thymic-dependent lymphocytes were sparse in lymph nodes and spleen. The abnormal lymphopoiesis in the syndrome probably results from a subtle immunodeficiency, and concurrent measles and EB virus infections.     

Large deletion of the X-linked lymphoproliferative disease gene detected by fluorescence in situ hybridization

The X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by an abnormal responses to infection with Epstein-Barr virus (EBV), resulting in fatal infectious mononucleosis, hypogammaglobulinemia, virus-associated hemophagocytic syndrome, and malignant lymphoma. Mutations in the gene coding for a T cell-specific SLAM-associated protein (SAP) have been recently identified in XLP patients. We report on a 1-year-old boy representing fulminant hemophagocytic syndrome. He developed high fever, lymphadenopathy, hepatosplenomegaly with liver dysfunction, and pancytopenia with marrow hemophagocytosis. EBV DNA was abnormally increased in the blood. Polymerase chain reaction failed to amplify SAP mRNA and genomic DNA products from the patient' As peripheral blood. A large deletion of the SAP gene was confirmed by fluorescence in situ hybridization (FISH). FISH analysis also disclosed that the patient's mother was a carrier. We conclude that FISH can be useful in the diagnosis of XLP with large deletions of the SAP gene and its carrier state.     

X-linked lymphoproliferative syndrome presenting with systemic lymphocytic vasculitis

X-linked lymphoproliferative syndrome (XLP) is a rare, often fatal, primary immunodeficiency disease characterized by an abnormal response to Epstein-Barr virus (EBV) infection. The gene responsible for XLP has been identified as SH2D1A/DSHP/SLAM-associated protein (SAP). The major clinical manifestations include fulminant infectious mononucleosis, lymphoproliferative disorder, and dysgammaglobulinemia. Affected males uncommonly present with lymphocytic vasculitis in addition to aplastic anemia. In this study, we describe a Japanese XLP patient who presented with hypogammaglobulinemia following acute EBV-induced infectious mononucleosis in the infancy and later had systemic lymphocytic vasculitis and hemophagocytic lymphohistiocytosis in the adulthood, which resolved by steroid pulse therapy. The patient's SAP gene was found to harbor a missense mutation (His8Asp), presumably resulting in defective expression of SAP in T cells. Biopsy specimens of lung and skin disclosed that CD8+ T cells predominantly infiltrated vascular vessels. However, immunohistochemical examination showed that EBV-infected cells were not identifiable in the vessels. We propose that T-cell-mediated immune dysregulation in XLP can cause vasculitis by EBV infection-unrelated mechanism.     

Allogeneic stem cell transplantation in X-linked lymphoproliferative disease: two cases in one family and review of the literature

X-linked lymphoproliferative disease (XLP) is a rare immunodeficiency caused by mutations in the signaling lymphocyte activating molecule-associated protein/SH2D1A gene and characterized by a dysregulated immune response to Epstein-Barr virus and other pathogens. The clinical presentation is heterogeneous and includes fulminant infectious mononucleosis, lymphoma, hypogammaglobulinemia and aplastic anemia. XLP is associated with a high morbidity and overall outcome is poor. At present, allogeneic stem cell transplantation (alloSCT) is the only curative treatment. XLP patients may be recognized in various stages of disease and even when symptoms are not yet evident. We here present two related XLP patients in different stages of disease that were both treated successfully with alloSCT using a matched unrelated donor. In addition, we have reviewed all reported cases of alloSCTs in XLP patients. Based on these results and in order to improve the final outcome, we conclude that alloSCT should be recommended in both symptomatic and asymptomatic XLP patients.     

Cell surface receptors Ly-9 and CD84 recruit the X-linked lymphoproliferative disease gene product SAP

X-linked lymphoproliferative disease (XLP) is a rare immune disorder commonly triggered by infection with Epstein-Barr virus. Major disease manifestations include fatal acute infectious mononucleosis, B-cell lymphoma, and progressive dys-gammaglobulinemia. SAP/SH2D1A, the product of the gene mutated in XLP, is a small protein that comprises a single SH2 domain and a short tail of 26 amino acids. SAP binds to a specific motif in the cytoplasmic tails of the cell surface receptors SLAM and 2B4, where it blocks recruitment of the phosphatase SHP-2. Here it is reported that Ly-9 and CD84, 2 related glycoproteins differentially expressed on hematopoietic cells, also recruit SAP. Interactions between SAP and Ly-9 or CD84 were analyzed using a novel yeast 2-hybrid system, by COS cell transfections and in lymphoid cells. Recruitment of SAP is most efficient when the specific tyrosine residues in the cytoplasmic tails of Ly-9 or CD84 are phosphorylated. It is concluded that in activated T cells, the SAP protein binds to and regulates signal transduction events initiated through the engagement of SLAM, 2B4, CD84, and Ly-9. This suggests that combinations of dysfunctional signaling pathways initiated by these 4 cell surface receptors may cause the complex phenotypes of XLP. (Blood. 2001;97:3867-3874)     

Correlation of mutations of the SH2D1A gene and epstein-barr virus infection with clinical phenotype and outcome in X-linked lymphoproliferative disease

The purposes of this study were to determine the frequency of mutations in SH2D1A in X-linked lymphoproliferative disease (XLP) and the role of SH2D1A mutations and Epstein-Barr virus (EBV) infection in determining the phenotype and outcome of patients with XLP. Analysis of 35 families from the XLP Registry revealed 28 different mutations in 34 families-large genomic deletions (n = 3), small intragenic deletions (n = 10), splice-site (n = 3), nonsense (n = 3), and missense (n = 9) mutations. No mutations were found in 25 males, so-called sporadic XLP (males with an XLP phenotype after EBV infection but no family history of XLP) or in 9 patients with chronic active EBV syndrome. Of 304 symptomatic males in the XLP Registry, 38 had no evidence of EBV infection at first clinical manifestation. When fulminant infectious mononucleosis (FIM) was excluded, there was no statistical difference in the frequency of EBV infectivity in the other XLP phenotypes. Furthermore, there was no difference at age of first clinical manifestation between EBV(+) and EBV(-) males or in survival when patients with FIM were excluded. In conclusion, it was found that mutations in the SH2D1A gene are responsible for XLP but that there is no correlation between genotype and phenotype or outcome. It was also found that though EBV infection often results in FIM, it is unnecessary for the expression of other manifestations of XLP, and it correlates poorly with outcome. These results suggest that unidentified factors, either environmental or genetic (eg, modifier genes), contribute to the pathogenesis of XLP.