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Biomedical subjects

B Bellon

Publications and source records attributed to B Bellon.

At least 55 records · Page 3Linked to original sources
PubMed1991

Prevention of experimental autoimmune uveoretinitis and experimental autoimmune pinealitis in (Lewis x Brown-Norway) F1 rats by HgCl2 injections.

Mercuric chloride (HgCl2) induces in Brown-Norway (BN) and (Lewis x Brown-Norway) F1 hybrid rats a transient autoimmune disease characterized by the production of various antibodies to self and non-self antigens and by a dramatic increase of serum IgE. Experimental autoimmune uveoretinitis (EAU) can be induced in Lewis (LEW) and (LEW x BN) F1 hybrid rats by a single immunization with retinal S-antigen (S-Ag). Besides uveoretinitis, animals immunized with S-Ag develop an autoimmune pinealitis (EAP). We demonstrate in this study that (LEW x BN) F1 hybrid rats, injected with HgCl2 7 days before S-Ag immunization, are quite efficiently protected against EAU and EAP. We also show that HgCl2-induced protection is neither due to a cytotoxic effect of HgCl2 nor to CD8+ T-cell dependent mechanisms nor to the HgCl2-induced increase of serum IgE concentration. The role of other hypothetical mechanisms, such as anti-S-Ag anti-idiotypic antibodies and/or HgCl2-induced unbalance between T-helper cell subsets, is discussed.

Animals↗
PubMed1990

Permeability of the normal rat brain, spinal cord and dorsal root ganglia microcirculations to immunoglobulins G.

The distribution of blood-borne immunoglobulins G (IgG) was studied in the cerebral cortex, pineal gland, spinal cord and dorsal root ganglia of normal Lewis rats using the detection of autologous anti-horseradish peroxidase (HRP) antibodies. This detection was performed by means of light and electron microscopy. This study demonstrated that, in the cerebral cortex and the spinal cord microcirculations, endothelial cells are a restrictive barrier against IgG while IgG are able to diffuse into the perivascular parenchyma of the pineal gland and spinal ganglia.

Animals↗
PubMed1990

Inhibition of experimental autoimmune uveoretinitis by mercuric chloride injections in (Lewis x Brown Norway) F1 hybrid rats.

Experimental autoimmune uveoretinitis (EAU), induced in (LEW X BN) F1 rats by immunization with S antigen (S-Ag) is T cell and antibody (ab) mediated and anti-S-Ag IgE ab have been involved in the occurrence of ocular lesions. (LEW X BN) F1 rats repeatedly injected with HgCl2 develop an autoimmune disease characterized by numerous auto-ab and a high increase of serum IgE level. We hypothesize that large amounts of non anti-S-Ag IgE induced by HgCl2 would compete with anti-S-Ag induced by S-Ag immunization so as to prevent EAU to occur. Indeed (LEW X BN) F1 rats immunized with S-Ag 7 days after the first HgCl2 injection are strongly protected against EAU. The putative role of the different mercury-induced autoimmune phenomena in the protection against EAU are discussed.

Animals↗
PubMed1989

Inhibitory properties and antigenic specificity of monoclonal antibodies to pancreatic colipase.

To understand the mechanism by which colipase acts as a protein cofactor for anchoring pancreatic lipase at triacylglycerol/water interface, we have used an immunochemical approach. Ten monoclonal antibodies (Mabs) against porcine pancreatic procolipase were produced. Purified immunoglobulins and Fab fragments were studied for their capacity to inhibit colipase-dependent lipase activity. These studies were carried out by using procolipase, the secretory form of the cofactor, and its trypsin-treated form obtained by removal of the amino terminal pentapeptide by trypsin. Reactivities of Mabs with both forms of the cofactor were also studied by immunoenzymatic methods. Mabs 6.1, 49.20. 75.8, 270.13 and 419.1 were found to inhibit lipolysis by preventing the binding of procolipase or trypsin-treated colipase to the lipid substrate. Mab 72.11 inhibited procolipase binding but had no effect on trypsin-treated colipase. Mab 72.11 reacted with procolipase in ELISA but showed no reactivity with trypsin-treated colipase. Finally, preincubation of Mab 72.11 with porcine procolipase prevented specific cleavage at the Arg5-Gly6 bond by trypsin. It could be concluded, that the five first residues of procolipase are structural elements of the antigenic determinant recognized by Mab 72.11. Results of ELISA additivity tests (cotitrations) further indicated that epitopes for Mabs 6.1, 72.11, 270.13 and 419.1 and for Mabs 49.20 and 75.8 are located in two distinct antigenic regions of the procolipase molecule. It appears then that the lipid binding domain of the pancreatic lipase protein cofactor comprises two regions. The first region corresponds to the amino terminal fragment of the protein. The second region is likely identical with the peptide segment at position 51-59 as previously hypothesized from NMR and spectrophotometric studies. Studies carried out on procolipase chemically modified at tyrosine residues provided evidence that epitopes for Mabs 49.20 and 75.8 are in or close to the region which contains tyrosines at positions 55 and 59, and that the two peptide regions essential for interfacial binding are spatially adjacent in the procolipase and the trypsin-treated form of the cofactor. General conclusions are in accordance with the location of antigenic regions of procolipase determined by predictive methods.

Animals↗
PubMed1988

Apple Macintosh programs for nucleic and protein sequence analyses.

This paper describes a package of programs for handling and analyzing nucleic acid and protein sequences using the Apple Macintosh microcomputer. There are three important features of these programs: first, because of the now classical Macintosh interface the programs can be easily used by persons with little or no computer experience. Second, it is possible to save all the data, written in an editable scrolling text window or drawn in a graphic window, as files that can be directly used either as word processing documents or as picture documents. Third, sequences can be easily exchanged with any other computer. The package is composed of thirteen programs, written in Pascal programming language.

Amino Acid Sequence↗
PubMed1988

Construction of restriction maps.

A computer program is described, which constructs maps of restriction endonuclease cleavage sites in linear or circular DNA molecules, given the fragment lengths in single and double digestions with two enzymes. The algorithm is based upon a partition method and a very simple rule to chain fragments. The program is written in Prolog II.

Algorithms↗
PubMed1987

High frequency of autoantibodies bearing cross-reactive idiotopes among hybridomas using VH7183 genes prepared from normal and autoimmune murine strains.

Hybridomas obtained by in vitro stimulation with lipopolysaccharides (LPS) of BALB/c, MRL/lpr, and NZB splenocytes were selected for expression of VH7183 by hybridization using slot blotting. Northern blot analysis showed that the majority of hybrids produce a full length message complementary to the VH7183 probe. The frequency of VH7183 hybridomas was significantly higher in NZB mice as compared with BALB/c mice. Using multiple binding assays, 60% of the total antibodies encoded by VH7183 were specific for self-epitopes. Finally, the vast majority express cross-reactive idiotypes borne by autoantibodies of various specificities.

Animals↗
PubMed1986

Fine specificity, idiotypy, and nature of cloned heavy-chain variable region genes of murine monoclonal rheumatoid factor antibodies.

We investigated the immunochemical and molecular characteristics of murine monoclonal rheumatoid factors. Study of the fine specificity of 20 monoclonal rheumatoid factor antibodies shows a wide degree of heterogeneity. However, many express an interstrain cross-reactive idiotype. We show that our rheumatoid factors utilize a restricted set of the heavy-chain variable region (VH) repertoire representing the more 3' VH families. Preferential expression of 3' VH families is known to occur early in development. We report the nucleotide sequence of two cloned rheumatoid factor VH genes, Y19-10 (VH J558) and 129-48 (VH 7183) in which no major differences are observed between VH genes encoding the heavy chain of autoantibodies and antibodies against foreign antigens.

Animals↗
PubMed1986

Shared idiotypes and restricted immunoglobulin variable region heavy chain genes characterize murine autoantibodies of various specificities.

The study of the Ig variable region heavy chain (VH) genes used to encode antibodies specific for self-epitopes from murine hybridomas showed that three VH families are primarily utilized: VH J558, the largest family, and VH QPC52 and VH 7183, the families most proximal to the Ig joining region heavy chain genes. These monoclonal autoantibodies express cross-reactive idiotopes shared by rheumatoid factors and antibodies specific for Sm. The expression of these idiotypes is independent of major histocompatibility complex and Ig constant region heavy chain haplotypes, self-antigen specificity, and even the VH gene family utilized. Though the experiments described here are limited to murine autoantibodies, similarities exist between murine and human autoimmune diseases. Studies that aim to investigate the relationship between VH gene expression and the presence of cross-reactive idiotypes among human autoantibodies should enable us to better understand the mechanisms of autoimmunity and self-tolerance.

Animals↗
PubMed1986

Protein transfer in hyperoxic induced pleural effusion in the rat.

In order to study the kinetics and pathways of protein transfer in pleural effusion, rats with pleurisy associated with hyperoxic pulmonary edema were injected either intrapleurally or intravenously with tracers. 125I-Albumin was used to obtain quantitative data. Anti horseradish peroxidase used as a morphological tracer, allowed a precise localization of the pathways used for the transfer. It has been possible to demonstrate that, in this model, the pleural effusion is produced by a plasma exudation accumulated in the lung interstitium, transferred through the visceral pleura and resorbed by the lymphatics of the parietal costal and diaphragmatic pleurae.

Albumins↗
PubMed1985

Immunochemical and molecular characterization of regulatory idiotopes expressed by monoclonal antibodies exhibiting or lacking beta 2-6 fructosan binding activity.

Hybridomas secreting antibodies bearing the ABPC48 (A48) regulatory idiotype (Id) were generated from BALB/c mice treated at birth or as adults with minute amounts of anti-A48-Id antibodies. The majority of these antibodies were recognized by the syngeneic monoclonal anti-A48-Id and anti-UPC-10-Id antibodies, IDA10 and 10-1, respectively. In Northern blotting experiments, most of these hybridomas were shown to use VH (heavy chain variable region) genes related to the 441-4 germline VH gene that encodes the A48 VH region. Hybridization was detected between polyadenylated H chain mRNA, isolated from the majority of the hybridomas, and the VH probe. Southern blots confirmed these results by showing a rearrangement of VH-related sequences to the JH (H chain joining segment) clusters on these same hybridomas. The antibodies from all of the hybridomas that derived from neonatal mice and half of those derived from adult mice showed specificity for fructosan determinants that, in most cases, was different from the beta 2-6 fructosan linkage specificity of A48. Surprisingly, several of the non-fructosan-binding hybridomas generated from the adult mice and the MOPC-173 myeloma demonstrated a clear specificity for the beta 1-6-D-galactan determinant. Of four galactan-binding myeloma proteins studied. XRPC 44 alone shared idiotypy with the UPC-10 myeloma. These findings suggest a possible clonal crossreactive regulation mediated by regulatory idiotopes. The crossreactive regulation concept is discussed.

Animals↗
PubMed1984

Apple II PASCAL programs for molecular biologists.

A collection of PASCAL programs designed for the Apple II microcomputer is presented. These DNA sequence handling and analysis programs are interactive and may be used even by people with no computer experience. The package allows the user to enter a sequence from the keyboard, to modify it, to generate the reverse complement, to create new sequences from parts of other ones, to display or print sequences in various formats. Some analysis tasks are also performed: Translation, searches for restriction sites, for homology with subsequences, either perfect or with an adjustable match percentage. In addition, two programs are also included: The first one allows DNA data sequences generated with a BASIC program under the CP/M operating system to be used with these PASCAL programs. The second one is designed for the automatic assembly of DNA fragments sequences, obtained with the GILBERT-MAXAM or M13 techniques, into a complete sequence.

Amino Acid Sequence↗
PubMed1984

Electron-microscopic immunohistochemical study of the localization of immunoglobulin G in the choroid plexus of the rat.

The localization of autologous antiperoxidase immunoglobulin G (IgG) was studied in the choroid plexus of Lewis rats immunized against horseradish peroxidase (HRP). This experiment was performed to study the permeability of the choroid plexus to intravascular IgG. It was shown that autologous IgG was present in the extravascular spaces. The transendothelial transfer appeared to occur mainly via the fenestrations and some interendothelial junctions. No transfer of IgG at the level of epithelial cells toward the cerebrospinal fluid was demonstrated. Interstitial spaces in contact with the connective-tissue cells of the choroid stroma were strongly labeled. The significance of these spaces remains hypothetical and raises the question of the fate of IgG from the interstitial space.

Animals↗
PubMed1984

IgG Fc membrane receptor on normal human glomerular visceral epithelial cells.

This study demonstrates that human glomerular epithelial cells are able to bind heat aggregated immunoglobulins and antigen-antibody complexes. This has been observed on kidney cryostat sections, on whole glomeruli and on cultured visceral epithelial cells. Binding depends on the presence of the Fc portion of IgG and occurs in the absence of complement, showing that the IgG Fc receptor is different from the C3b receptor. The use of heat aggregated anti-peroxidase IgG and of peroxidase anti-peroxidase complexes allowed us to demonstrate, at the ultrastructural level, that the binding of the reagents at the plasma membrane was followed by their internalization within coated pits of vesicles. These observations strongly suggest that glomerular visceral epithelial cells are capable of receptor mediated endocytosis. The role of this process in glomerular diseases remains to be established.

Antigen-Antibody Complex↗