Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0021345 (infectious mononucleosis)
3,358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

X-linked lymphoproliferative syndrome (XLP) is an immunodeficiency characterized by life-threatening infectious mononucleosis and EBV-induced B cell lymphoma. The gene mutated in XLP encodes SLAM (signaling lymphocytic activation molecule-associated protein)-associated protein (SAP), a small SH2 domain-containing protein. SAP associates with 2B4 and SLAM, activating receptors expressed by NK and T cells, and prevents recruitment of SH2 domain-containing protein tyrosine phosphatase-2 SHP-2) to the cytoplasmic domains of these receptors. The phenotype of XLP may therefore result from perturbed signaling through SAP-associating receptors. We have addressed the functional consequence of SAP deficiency on 2B4-mediated NK cell activation. Ligating 2B4 on normal human NK cells with anti-2B4 mAb or interaction with transfectants bearing the 2B4 ligand CD48 induced NK cell cytotoxicity. In contrast, ligation of 2B4 on NK cells from a SAP-deficient XLP patient failed to initiate cytotoxicity. Despite this, CD2 or CD16-induced cytotoxicity of SAP-deficient NK cells was similar to that of normal NK cells. Thus, selective impairment of 2B4-mediated NK cell activation may contribute to the immunopathology of XLP.
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PMID:Functional requirement for SAP in 2B4-mediated activation of human natural killer cells as revealed by the X-linked lymphoproliferative syndrome. 1097 98

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)
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PMID:Cell surface receptors Ly-9 and CD84 recruit the X-linked lymphoproliferative disease gene product SAP. 1138 28

The unique manifestation of the inherited immunodeficiency, X-linked lymphoproliferative disease (XLP), is the impaired control of EBV infection. The gene, which carries mutations or is deleted in the patients, has been identified (Xq25). The encoded protein (SAP, 128 aa) contains a single SH2 domain and binds to signaling lymphocytic activation molecule (SLAM) and to other related surface molecules that are expressed on activated T, B and NK cells. SAP modifies signal transduction through its association with these molecules. Initially it was assumed that SAP acts passively by interfering and blocking active interactions involving other SH2 carrying molecules. We demonstrated that SAP protein is expressed in activated T and NK, but not in activated B cells. This finding is in line with the fact that in vitro performance of effector cells derived from XLP patients is impaired. However, it is still not known why the severe symptoms (fatal mononucleosis or malignant lymphoproliferation in the survivors of the primary infection) are elicited by EBV. We studied SAP expression in several Burkitt lymphoma (BL) derived lines. In contrast to normal B cells, certain lines expressed SAP. These were all type I cells in the Burkitt line nomenclature: they expressed only one of the EBV encoded proteins (EBNA-1) and their phenotype corresponded to resting B cells. Lymphoblastoid cell lines and type III BLs, whose phenotype resembled activated B cells and expressed all nine EBV encoded proteins, were devoid of SAP. The relationship between cell activation and SAP expression is reciprocal in T and B cells i.e. BL lines, activated T and NK cells express SAP, while BL blasts do not express SAP. This opposite relationship may be exploited for studies about the function of SAP.
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PMID:The X-linked lymphoproliferative disease gene product SAP is expressed in activated T and NK cells. 1200 45

X-linked lymphoproliferative disorder (XLP) was first described almost 30 years ago; remarkably, the three major manifestations of XLP, fulminant infectious mononucleosis (FIM), lymphoma, and dysgammaglobulinemia, are all described in the report of the initial kindred. Subsequent establishment of an XLP registry has led to recognition of more unusual phenotypes in affected males; concurrently, much progress has been made in caring for boys with XLP, including treatment for the three major phenotypes, and curative bone marrow transplantation (BMT). The immunologic and genetic mechanisms resulting in XLP have also been intensively studied. Several years ago, the gene defective in XLP was identified as SAP (SLAM-associated protein), and recent data suggest that SAP plays a broad role in immune signaling. Here, we review the clinical manifestations and therapy of XLP, and briefly summarize recent research into the structure and function of SAP.
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PMID:X-linked lymphoproliferative disease: genetic lesions and clinical consequences. 1216 1

Mutations in SH2D1A, a gene that codifies for the regulatory protein SAP, result in uncontrolled activation of the SLAM (signaling lymphocyte-activation molecule) pathway. This X-linked immunodeficiency becomes evident when the patients are infected with Epstein Barr virus (EBV) and develop a fulminant form of infectious mononucleosis leading to a lymphoproliferative syndrome that is often fatal (X-linked lymphoproliferative syndrome, XLP). In those who survive, hypogammaglobulinemia and oncohematologic diseases are frequently observed. In this revision, the immuno-regulatory mechanisms involved in XLP immunopathology and the role of different effector cells (CD8 T lymphocytes, NK cells) are discussed.
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PMID:[X-linked lymphoproliferative syndrome, EBV virus infection and defects in cytotoxicity lymphocyte regulation]. 1267 66

Most Epstein-Barr virus (EBV) infections in infants and children are asymptomatic, while infection of adolescents or adults often results in infectious mononucleosis. The symptoms of infectious mononucleosis are primarily due to the T-cell proliferative response to EBV-infected B cells; thus, antiviral therapy does not affect the clinical course of disease. Failure of the cellular immune response to control EBV-induced B-cell proliferation can result in severe disease. Patients with the X-linked lymphoproliferative disease (XLPD) have a mutation in the SAP gene and EBV infection often leads to fatal infectious mononucleosis. Transplant recipients may develop lymphoproliferative disease, which often responds to treatment that enhances the immune response against EBV-infected B cells. About 50% of Hodgkin's and 20% of Burkitt's lymphomas in the United States contain EBV DNA. While chemotherapy and/or radiation therapy are mainstays of treatment, clinical trials are being developed using cytotoxic T cells directed against EBV proteins in these tumors.
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PMID:Benign and malignant Epstein-Barr virus-associated B-cell lymphoproliferative diseases. 1270 88

The symptoms of infectious mononucleosis (IM) are thought to be caused by T cell activation and cytokine production. Surface lymphocyte activation marker (SLAM)-associated protein (SAP) regulates lymphocyte activation via signals from cell-surface CD244 (2B4) and SLAM (CD150). We followed T cell activation via this SAP/SLAM/CD244 pathway in IM and analyzed whether the results were associated with clinical severity. At diagnosis, SAP, SLAM, and CD244 were significantly up-regulated on CD4 and CD8 T cells; expression decreased during IM, but CD244 and SLAM levels remained higher on CD8 cells 40 days later. There were significantly more lymphocytes expressing CD8 and CD244/CD8 in patients with severe sore throat. The expression of CD8 alone and CD244 on CD8 cells correlated with increased virus load. We suggest that T cells expressing CD244 and SLAM are responsible for the clinical features of IM but that the control of activation is maintained by parallel increased expression of SAP.
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PMID:Analysis of immune activation and clinical events in acute infectious mononucleosis. 1519 44

X-linked lymphoproliferative disease (XLP) is an inherited immune defect caused by mutations in the Src homology 2 domain-containing gene 1A, which encodes the adapter protein, signaling lymphocytic activation molecule (SLAM)-associated protein (SAP). SAP is expressed in T cells, natural killer (NK) cells, and NKT cells, where it binds to the cytoplasmic domain of the surface receptor SLAM (CD150) and the related receptors, 2B4 (CD244), CD84, Ly9 (CD229), NK-T-B-antigen, and CD2-like receptor-activating cytotoxic T cells. SAP also binds to the Src family tyrosine kinase Fyn and recruits it to SLAM, which leads to the generation of downstream phosphotyrosine signals. While the roles of the SLAM family receptors are only beginning to be understood, experiments suggest that these molecules regulate important aspects of lymphocyte function, such as proliferation, cytokine secretion, cytotoxicity, and antibody production. Thus, in XLP patients who lack functional SAP, the SLAM family receptors may not signal properly. This property likely contributes to the phenotypes of XLP, including fulminant infectious mononucleosis, lymphoma, and hypogammaglobulinemia. Further studies of SAP and the SLAM family receptors will provide insights into XLP and elucidate the signaling events regulating lymphocyte ontogeny and function.
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PMID:Molecular and cellular pathogenesis of X-linked lymphoproliferative disease. 1566 Oct 30

X-linked lymphoproliferative disease (XLP) is an often-fatal immunodeficiency characterized by hypogammaglobulinemia, fulminant infectious mononucleosis, and/or lymphoma. The genetic lesion in XLP, SH2D1A, encodes the adaptor protein SAP (signaling lymphocytic activation molecule-associated [SLAM-associated] protein); however, the mechanism(s) by which mutations in SH2D1A causes hypogammaglobulinemia is unknown. Our analysis of 14 XLP patients revealed normal B cell development but a marked reduction in the number of memory B cells. The few memory cells detected were IgM(+), revealing deficient isotype switching in vivo. However, XLP B cells underwent proliferation and differentiation in vitro as efficiently as control B cells, which indicates that the block in differentiation in vivo is B cell extrinsic. This possibility is supported by the finding that XLP CD4(+) T cells did not efficiently differentiate into IL-10(+) effector cells or provide optimal B cell help in vitro. Importantly, the B cell help provided by SAP-deficient CD4(+) T cells was improved by provision of exogenous IL-10 or ectopic expression of SAP, which resulted in increased IL-10 production by T cells. XLP CD4(+) T cells also failed to efficiently upregulate expression of inducible costimulator (ICOS), a potent inducer of IL-10 production by CD4(+) T cells. Thus, insufficient IL-10 production may contribute to hypogammaglobulinemia in XLP. This finding suggests new strategies for treating this immunodeficiency.
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PMID:Impaired humoral immunity in X-linked lymphoproliferative disease is associated with defective IL-10 production by CD4+ T cells. 1576 93

Males with an expressed mutation in the SH2D1A gene that encodes an SH2 domain protein named SH2D1A or SAP (NP_002342; signaling lymphocyte activating molecule [SLAM]-associated protein), have an X-linked syndrome characterized by an increased vulnerability to infection with Epstein-Barr virus (EBV). We evaluated two related male patients with fatal infectious mononucleosis (FIM) and mutation in the SH2D1A gene. Sequence analysis revealed a hemizygous c.47G>A mutation in one of the patients, and heterozygosity for this mutation in the genomic DNA from his mother and maternal grandmother. This mutation resulted in p.G16D amino acid change in the sequence of the SAP protein. To analyze the effect of this missense mutation on protein function cDNA was generated by site-directed mutagenesis and expressed in COS cells. We found that half-life of the p.G16D protein was comparable to that of wild type SAP. However, the mutant protein was defective in binding to its physiological ligands SLAM and 2B4. These results suggest that a defect in ligand binding contributes to the loss of function of the SAP protein in patients carrying p.G16D mutation.
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PMID:Characterization of a new disease-causing mutation of SH2D1A in a family with X-linked lymphoproliferative disease. 1584 90


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