Infection of human thymocytes by Epstein-Barr virus.

The Epstein-Barr Virus (EBV) causes infectious mononucleosis, and has been strongly associated with certain human cancers. The virus is thought to exclusively bind to B lymphocytes and epithelial cells via receptors (CR2/CD21) that also interact with fragments of the third component of complement (C3). Recent evidence, however, has challenged this belief. We have used two-color immunofluorescence analysis using biotin-conjugated EBV and streptavidin-phycoerythrin along with fluorescein-conjugated anti-T cell antibodies and demonstrated that CD1-positive, CD3-dull (immature) human thymocytes express functional EBV receptors. In four replicate experiments, the binding of EBV to thymocytes ranged between 8 and 18%. This interaction is specific as evidenced by inhibition with nonconjugated virus, anti-CR2 antibodies, aggregated C3, and an antibody to the gp350 viral glycoprotein that the virus uses to bind to CR2. EBV can infect the thymocytes as evaluated by the presence of episomal EBV-DNA in thymocytes that had been incubated with the virus as short as 12 days or as long as 6 weeks. Episomal DNA analysis was performed by Southern blotting with a EBV-DNA probe that hybridizes to the first internal reiteration of the viral DNA. The presence of the EBV genome is also supported by the detection of EBV nuclear antigen 1 in infected thymocytes, assessed by Western blotting with EBV-immune sera. The EBV infection is specific as determined by blocking experiments using anti-CR2 and anti-gp350 antibodies. Finally, virus infection of thymocytes can act synergistically along with interleukin 2 and induce a lymphokine-dependent cellular proliferation. In view of previously reported cases of EBV-positive human T cell lymphomas, the possibility is raised that EBV may be involved in cancers of T lymphocytes that have not been previously appreciated.

A new surgical and technical approach in zygomatic implantology.

PURPOSE: Different surgical approaches for zygomatic implantology using new designed implants are reported. MATERIAL AND METHODS: The surgical technique is described and two cases reported. The zygomatic fixture has a complete extrasinus path in order to preserve the sinus membrane and to avoid any post-surgical sinus sequelae. RESULTS: The surgical procedure allows an optimal position of the implant and consequently an ideal emergence of the fixture on the alveolar crest. CONCLUSION: The surgical procedures and the zygomatic implant design reduce remarkably the serious post-operative sequelae due to the intrasinus path of the zygomatic fixtures.

Application of the MAILA technique to the study of human anti-HLA monoclonal antibody specificity.

The monoclonal antibody-specific immobilization of lymphocyte antigens (MAILA) assay was developed to detect antibodies present in human alloantisera against antigens of different major histocompatibility complex loci, particularly of class II specificity. The MAILA assay has been used in our laboratory to the determination of the type of HLA molecule recognized by human monoclonal antibodies 91C2 (anti-A2 + 28), 34F11 (anti-DQ1), and 2A2 (anti-DQ1 + 4 + short DQ7), using well characterized monomorphic as well as polymorphic murine monoclonals for the specific immobilization of HLA molecules. Results obtained show that the MAILA assay is also a valuable tool for the determination of specific human MHC locus products recognized by human monoclonal antibodies.

A human monoclonal antibody reacting against HLA-DQ1-, DQ4-, and a subset of DQ7-bearing cells.

Human mAb 2A2 recognizes an epitope present in the HLA-DQ1 + 4 specifications and also on several DQ7-positive cells. We have investigated the extra reactions of this monoclonal reagent on a wider panel of DQ1-, DQ4-negative/DQ7-positive B-cell lines. The results obtained support the existence of two subtypes of the HLA-DQ7 specificity on the basis of their reactivity with human mAb 2A2; the DQ7/2A2-positive variant has been found in 12 of 29 BCLs positive for the DR11 antigen, and in four of eight BCLs bearing DR4-DQ7 haplotypes. It has also been detected in the DR12-positive cells assayed and in several unusual DR/DQ7 combinations not commonly found in Caucasoid populations, including the DR13-DwHAG and DR14-Dw16 haplotypes. Results from competition binding assays between 2A2 and well-characterized murine anti-DQ polymorphic mAbs suggest that the epitope recognized by human mAb 2A2 on DQ1- or DQ4-bearing haplotypes is located on the DQ beta chains of such specificities, being amino acid residues 54-55, the potential binding site of antibody 2A2, whereas the binding site on DQ7 antigens cannot be explained on the basis of known amino acid sequences.

Porcelain CAD-CAM veneers. Some new uses explored.

With a new CAD-CAM technique, we restored and provided esthetic treatment for both natural teeth and fixed prostheses with worn or broken surfaces.

Where is the gap? Machinable ceramic systems and conventional laboratory restorations at a glance.

Scanning electron microscopy was used to compare the marginal gaps of restorations milled by machinable ceramic systems to the marginal gaps of conventional laboratory-sintered ceramic restorations. For occlusal surfaces, the average marginal gap was 80 microns for both laboratory- and Celay-produced inlays. The mean gap was 200 microns and 170 microns, respectively, for Cerec T (turbine motor) and Cerec EM (electric motor) inlays. For approximal boxes, the average marginal gap was 100 microns for inlays produced with conventional laboratory-sintering techniques, 80 microns for Celay restorations, and 280 microns for the Cerec T restorations, and 260 microns for Cerec EM-machined inlays. The ceramics used, as well as the different systems themselves, can influence the results and the clinical outcome of the restorations.

Rescue of a "hopeless" second premolar.

We present a case of a young male who was referred to our clinic because of a deep caries on the first lower left molar. The patient refused conservative treatment, and the caries progressed. After 2 years the first lower left molar had to be extracted. During standard x-ray procedures, a deeply impacted second lower left premolar was diagnosed. The boy was followed by our staff, and surgery was performed at proper time to enable eruption of the second lower left premolar. Orthodontic treatment allowed us to bring the element in a suitable position to place a provisional Maryland bridge. At a later stage the missing element (first lower left molar) will be replaced by an osteointegrated implant.

The CELAY system: a comparison of the fit of direct and indirect fabrication techniques.

CELAY is a machinable ceramic system that is capable of milling inlays, onlays, and veneers from prefabricated industrial ceramic blocks. Direct intraoral or indirect patterns may be used to make ceramic restorations. Scanning electron microscopy was used to analyze the marginal gap of restorations obtained with both methods. The direct fabrication technique yielded significantly better marginal gap sizes (P < .01) for the interproximal areas, while with the indirect (P < .01) fabrication technique the restorations showed significantly smaller marginal gaps at the occlusal borders. The clinical relevance of these findings and their possible applications for the development of a new impression material are discussed.

HIV-1-specific B cell activation. A major constituent of spontaneous B cell activation during HIV-1 infection.

B cell activation is a well known consequence of HIV-1 infection, and seropositive subjects show high numbers of spontaneously activated Ig-secreting cells in circulation. To better define the importance of the HIV-1-specific response in this phenomenon, we first studied whether in vitro spontaneous anti-HIV-1 antibody production was accompanied by reactivation of memory B lymphocytes. Unstimulated PBL from HIV-1-infected individuals with prior history of hepatitis B and/or EBV infection did not consistently show spontaneous in vitro synthesis of anti-hepatitis B core Ag or anti-EBV antibodies; in addition, PWM-induced synthesis of anti-hepatitis B virus and anti-EBV antibodies was decreased compared to HIV-1-seronegative subjects. Moreover, in comparing the frequencies of activated HIV-1-specific B cell precursors and activated Ig-secreting precursors in limiting dilution experiments, a sizable fraction (20 to 40%) of circulating cells spontaneously secreting Ig produced antibody against HIV-1 determinants. The ratio between the two frequencies fitted in very well with the amount of Ig removed from unstimulated culture supernatants after HIV-1-specific antibody absorption with solid-phase HIV-1. These findings indicate that B cell activation during HIV-1 infection is mainly oriented toward a specific response to HIV-1 determinants; the possible relevance of this phenomenon to lymphomagenesis in AIDS patients is discussed.