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immunoglobulin genes. Epidemiological studies have reported a high prevalence of B cell non-Hodgkin lymphoma (NHL) in HCV-positive patients, suggesting a potential association between HCV and Epstein-Barr virus (EBV) in the genesis of B lymphocyte proliferative disorders. In the present study, in order to investigate the association between EBV and HCV in B cells, we created an in vitro EBV-induced B cell transformation model. CD81 was gradually overexpressed during transformation by EBV. B cells isolated from HCV-positive patients grew more rapidly and clumped together earlier than B cells isolated from healthy donors following EBV infection. Pre-stimulation of CD81 expressed by resting B cells with anti-CD81 monoclonal antibody (mAb) or HCV E2 accelerated the generation of lymphoblastoid cell lines (LCLs) by EBV infection. These cells proliferated prominently through the early expression of interleukin-10 and intracellular latent membrane protein (LMP)-l. By contrast, the overexpression of CD81 on EBV-transformed B cells by anti-CD81 mAb or HCV E2 protein induced apoptosis through reactive oxygen species (ROS)-mediated mitochondrial dysfunction. These results suggest that the engagement of CD81 expressed by B cells has differential effects on B cell fate (proliferation or apoptosis) according to EBV infection and the expression level of CD81.

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yle='font-weight:700;'>CD81 in this process is disputed. Here, we generated cell culture infectious strain JFH1 HCV (HCVcc) genomes carrying an alanine substitution of E2 residues W529 or D535 that are critical for binding to CD81 and infectivity. Co-cultivation of these cells with naive cells expressing enhanced green fluorescent protein (EGFP) resulted in a small number of cells co-expressing both EGFP and HCV NS5A, showing that the HCVcc mutants are capable of cell-to-cell spread. In contrast, no cell-to-cell transmission from JFH1(DeltaE1E2)-transfected cells occurred, indicating that the HCV glycoproteins are essential for this process. The frequency of cell-to-cell transmission of JFH1(W529A) was unaffected by the presence of neutralizing antibodies that inhibit E2-CD81 interactions. By using cell lines that expressed little or no CD81 and that were refractive to infection with cell-free virus, we showed that the occurrence of viral cell-to-cell transmission is not influenced by the levels of CD81 on either donor or recipient cells. Thus, our results show that CD81 plays no role in the cell-to-cell spread of HCVcc and that this mode of transmission is shielded from neutralizing antibodies. These data suggest that therapeutic interventions targeting the entry of cell-free HCV may not be sufficient in controlling an ongoing chronic infection, but need to be complemented by additional strategies aimed at disrupting direct cell-to-cell viral transmission.

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ll lines. This molecule was identified, after immunoaffinity purification and mass spectrometry analysis, as the protein encoded by the KIAA1436 gene and the human ortholog of a rat protein known as FPRP. Cross-linking experiments detected a complex of the size of CD9 plus CD9P-1, showing that these glycoproteins directly associate with each other, probably in the absence of any other molecule. The use of chimeric CD9/CD82 molecules revealed the role of the second half of CD9, comprising the large extracellular loop and the fourth transmembrane domain. CD9P-1 was also shown to form separate complexes with CD81 and with an unidentified 175-kDa molecule. It also associated with other tetraspanins under conditions maintaining tetraspanin/tetraspanin interactions. The identification of a protein strongly linked to the tetraspanin web and the production of a specific monoclonal antibody will help to further characterize the role of this "web" under physiological and pathological conditions.

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ed tissues and contributing to inflammation and fibrosis. The aim of this study was to characterize the blood eosinophils in SSc patients. METHOD: Expression levels of surface markers CD11b, CD44, CD48, CD54, CD69, CD81, and HLA-DR on CD16(low)CD9(high)-expressing eosinophils were measured by flow cytometry in whole blood from SSc patients (n = 32) and controls (n = 11). RESULTS: Expression levels of CD54, CD69, and HLA-DR were undetectable in all groups. CD44 and CD11b expression levels were similar between groups. CD81 expression was lower in patients compared to controls independent of disease duration (p = 0.001). CD48 expression was increased in patients with a short disease duration (< 2 years) compared to both controls (p = 0.042) and patients with longer disease duration (>/= 2 years; p = 0.027). In patients with short disease duration, increased CD48 expression was associated with alveolar inflammation as measured by an increased concentration of alveolar nitric oxide (r = 0.76, p = 0.003). CONCLUSIONS: Blood eosinophils change phenotype during disease evolution in SSc, and CD48 expression may be used as a biomarker for pulmonary inflammation.

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ght:700;'>CD81 in the cultures was defined by immunoblot methods, and the distribution of the protein was examined using indirect immunohistochemical methods. In addition, the effects of the antibody binding were tested in culture. RESULTS: CD81 was found in all layers of the normal retina with a distinct absence of labeling in the inner and outer segments of the photoreceptors. Based on the authors' original immunohistochemical analysis, it was difficult to determine whether CD81 was expressed by RPE. By examining cultures of RPE it was demonstrated that CD81 was expressed on the surface of these cells and that it was concentrated at regions of cell-cell contact. Indirect immunohistochemical methods using a peroxidase-labeled secondary antibody in albino mice revealed heavy labeling of the RPE in the intact eye. When the AMP1 antibody (directed against the large extracellular loop of CD81) was added to cultured RPE, the mitotic activity of the cells was depressed. CONCLUSIONS: CD81 was found in the normal rat retina. Previous studies demonstrated that CD81 was expressed in retinal glia, the Muller cells that span the thickness of the retina, and astrocytes found in the ganglion cell layer. The present study demonstrated that CD81 was also expressed by RPE. The dramatic effects of the AMP1 antibody and the location of CD81 at regions of cell-cell contact support the hypothesis that this molecule is part of a molecular switch controlling contact inhibition.

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in a temporal and spatial pattern during development that was consistent with CD9 expression in OPCs just prior to their differentiation into premyelinating oligodendrocytes. NG2-positive cells in mature brains were CD9-negative. CD9 expression during oligodendrocyte development in vitro supported this hypothesis, as all CD9-positive cells became O4-positive when switched to oligodendrocyte differentiating media. CD9 immunoreactivity was enriched in myelinating oligodendrocytes and their processes, and the outer aspects of myelin internodes. Immunoprecipitation of CD9 from postnatal rat cerebrum coprecipitated beta1 integrin, CD81, and Tspan-2, another tetraspanin protein recently identified in oligodendrocytes. Following surface biotinylation of oligodendrocytes in vitro, biotinylated beta1 integrin was identified in a CD9 immunoprecipitate. These data support a molecular link between surface integrins and a CD9, Tspan-2 molecular web during the differentiation of oligodendrocytes. Oligodendrocyte production and myelination appears to be normal in CD9-deficient mice. These data support the hypothesis that CD9 helps form the tetraspanin web beneath the plasma membranes of progenitor cells committed to oligodendrogenesis, but that CD9 is not essential for oligodendrogenesis and myelination.