Search PubMed⌕ Search

Biomedical subjects

E Depla

Publications and source records attributed to E Depla.

23 records · Page 2Linked to original sources
PubMed1993

Endonexin II, present on human liver plasma membranes, is a specific binding protein of small hepatitis B virus (HBV) envelope protein.

Binding of viral envelope proteins to specific receptors on human hepatocytes is considered to be an important step in HBV infection. In this study, we demonstrate that a 34-kDa human liver plasma membrane protein specifically binds to small HBsAg in a Ca(2+)-dependent manner. By partial amino acid sequence analysis of preparatively isolated 34-kDa protein comigrating with HBsAg-binding protein obtained from binding assay on IEF/SDS-PAGE, we have identified this HBsAg-binding protein as Endonexin II (E-II). Native human liver E-II inhibits binding of HBsAg to intact human hepatocytes and shows specific binding to small HBsAg. This binding can be inhibited by human liver plasma membrane proteins, recombinant E-II, or anti-E-II antibodies. Despite 90% sequence homology, rat liver E-II does not bind to small HBsAg and does not inhibit significantly (less than 20%) binding of HBsAg to intact hepatocytes. Cross-linking of small HBsAg and radiolabeled human liver E-II resulted in a specific additional protein complex on PAGE with an apparent molecular weight of 90 kDa, corresponding to a complex of E-II and small HBsAg with a ratio of 2 to 1 or 1 to 2. These findings indicate that E-II, found in human liver, is a specific HBsAg-binding protein and might play an important role in the initiation of HBV infection.

Amino Acid Sequence↗
PubMed1991

Anti-idiotypic and anti-anti-idiotypic antibodies as highly specific tools in epitope and active site studies on human interferon-gamma.

Immunization of rabbits with F(ab')2 fragments of different monoclonal antibodies directed against human interferon-gamma yielded antisera with anti-idiotypic characteristics. Isolation of the anti-idiotypic fraction, resulting in a highly specific antiserum, allowed us to prove that out of six competing monoclonal antibodies directed against human interferon-gamma, only two really recognize the same epitope. The other monoclonal antibodies compete on the basis of steric hindrance, which is not surprising, because of the large difference in Mr between interferon-gamma and an immunoglobulin. The anti-idiotypes provided us also with a tool to study isolated epitopes on the human interferon-gamma molecule, a task which was previously not practicable. Exploration of the biological properties of these anti-idiotypes allows us to determine whether the investigated epitopes are involved in receptor binding. The production of an anti-anti-idiotypic antiserum not only proved that we generated real internal images, but also that these images conserved all of their properties, although with a decreased affinity in comparison with the original monoclonal antibody. As the former is a polyclonal antiserum, directed against a single epitope of the human interferon-gamma molecule, competition experiments yielded additional information on the relative position of three epitopes recognized by inhibiting monoclonal antibodies. These antisera will possibly open new ways for the affinity purification of interferon-gamma and perhaps for the treatment of autoimmune diseases.

Animals↗
PubMed1991

Expression of interferon-gamma receptor in normal and pathological human liver tissue.

Using in situ immunohistochemistry and a specific monoclonal antibody (mcab R1G10), we analyzed the expression of the human interferon-gamma receptor (HuIFN-gamma R) and its topographical distribution in normal liver biopsies and in biopsies with various inflammatory liver diseases. In normal liver tissue, mcab R1G10 reacted weakly with sinusoidal and vascular endothelial cells, while hepatocytes were distinctly negative. In pathological conditions, mcab R1G10 produced membranous, cytoplasmic and/or perinuclear staining of hepatocytes, in a topographical distribution which varied according to the type of liver disease. In acute hepatitis, R1G10-positive hepatocytes were diffusely distributed throughout the liver parenchyma, and showed strong cytoplasmic, as well as membranous and perinuclear reactivity. In chronic persistent hepatitis, weak membranous staining was found on a number of scattered hepatocytes in acinar zone 1, with more pronounced expression on single hepatocytes in acinar zone 3. In chronic active hepatitis and in active cirrhosis, a diffuse weak membranous reactivity throughout the liver parenchyma was accompanied by enhanced R1G10 expression in areas of inflammation in acinar zone 1. With immunoelectronmicroscopy, R1G10 reactivity was found on the peripheral cell membrane and on the microvillous canalicular cell membrane of hepatocytes in a strikingly discontinuous manner. In the cytoplasm, the reaction product was detected on the cisternae of the rough endoplasmic reticulum and on small vesicles which were especially abundant in the perinuclear area. Our results demonstrate the absence of HuIFN-gamma R on hepatocytes in the normal liver, and its de novo expression during inflammatory liver disease. These findings indicate that hepatocytes, by displaying the HuIFN-gamma R, may act as target cells for the immunoregulatory action of IFN-gamma during liver inflammation.

Biopsy, Needle↗
PubMed1990

Monoclonal antibodies against the human interferon-gamma receptor(s).

Enriched human interferon-gamma (HuIFN-gamma) receptor preparations were obtained by affinity chromatography of non-ionic detergent solubilized COLO 205 cell membranes on immobilized recombinant HuIFN-gamma. The active fractions, identified by a competition ELISA, were used as the immunogen in a BALB/c mouse. Fusion of its splenocytes with myeloma cells yielded several hybrids secreting antibodies that inhibit the antiviral activity of HuIFN-gamma; the two most active ones were selected for further characterization. This blocking activity was restricted to both the human species and the gamma type of IFN. Affinity purification of cell membrane extracts on the immobilized monoclonal antibodies resulted in the visualization of a major protein band with an Mr of 90,000, which is in good agreement with the results obtained by other authors [Aguet M. and Merlin G. (1987) J. exp. Med. 165, 988-999; Novick D., Orchansky P., Revel M. and Rubinstein M. (1987) J. biol. Chem. 262, 8483-8487; Sheehan K. C. F., Calderon J. and Schreiber R. D. (1988) J. Immun. 140, 4231-4237].

Animals↗