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J Clot

Publications and source records attributed to J Clot.

At least 55 records · Page 3Linked to original sources
PubMed1993

Polymorphism in the regulatory region of HLA-DRB genes correlating with haplotype evolution.

Class II genes of the human major histocompatibility complex (MHC) are polymorphic. Allelic variation of the coding region of these genes is involved in the antigen presentation and is associated with susceptibility to certain autoimmune diseases. The DR region is unique among human class II regions in that multiple DRB genes are expressed. Differential expression of the different DRB loci has been demonstrated, and we sequenced the proximal promoter region of the HLA-DRB genes, known to be involved in the regulation of these genes. We found locus-specific and allele-specific nucleotide variations in their regulatory regions and we determined the relationship between the regulatory regions of HLA-DRB genes. This polymorphism found in the regulatory conserved boxes could be involved in the observed differential expression of DRB loci. In addition, we found a polymorphism between the regulatory regions of DRB1 alleles which might be involved in an allele-specific regulation and therefore could be considered as an additional factor in susceptibility to autoimmune diseases.

Base Sequence↗
PubMed1993

Investigation of the HLA component involved in rheumatoid arthritis (RA) by using the marker association-segregation chi-square (MASC) method: rejection of the unifying-shared-epitope hypothesis.

In order to investigate the HLA component involved in rheumatoid arthritis (RA), we tested genetic models by the marker association-segregation chi 2 (MASC) method, using the HLA genotypic distribution observed in a sample of 97 RA patients. First we tested models assuming the involvement of a susceptibility gene linked to the DR locus. We showed that the present data are compatible with a simple model assuming the effect of a recessive allele of a biallelic locus linked to the DR locus and without any assumption of synergistic effect. Then we considered models assuming the direct involvement of the DR allele products, and we tested the unifying-shared-epitope hypothesis, which has been proposed. Under this hypothesis the DR alleles are assumed to be directly involved in the susceptibility to the disease because of the presence of similar or identical amino acid sequences in position 70-74 of the third hypervariable region of the DRBI molecules, shared by the RA-associated DR alleles DR4Dw4, DR4Dw14, and DR1. This hypothesis was strongly rejected with the present data. In the case of the direct involvement of the DR alleles, hypotheses more complex than the unifying-shared-epitope hypothesis would have to be considered.

Adult↗
PubMed1993

[Isotypic regulation of antibodies and antibiotics].

Several reports have shown that antibiotics can in vitro interfere with many aspects of the immune response such as phagocytic processes, macrophage functions, T and B cell proliferation. Very few data on the effect of antibiotics on the antibody response were available. It is well known that the humoral immune response is sustained by different immunoglobulin isotypes (IgA, IgE, IgG or IgM) according to the antigen, its penetration route, the mucosal-associated lymphoid tissue, the genetic background and the age of the host. Such an isotypic regulation was very recently demonstrated to be closely related to some cytokines like interferon-gamma, interleukins (IL)-2, -4 and -10. We tested the effect of some cephalosporins on in vitro cytokine-dependent immunoglobulin production. Neither cefadroxil nor cefalexine had any modulating effect on pokeweed mitogen-induced IgG and IgM production by normal human B-cells. In contrast, cefadroxil, and not cefalexine, blocked up to 90% of the in vitro IL-4-dependent IgE production by normal B lymphocytes. In the same way, this cephalosporin was able to inhibit the membrane expression of CD23 molecules (low affinity Fc-epsilon-receptors) which is involved in phagocytic processes and in IgE regulation. The first target cell of the effect of cefadroxil was clearly shown to be monocyte-macrophage lineage which were stimulated to produce prostaglandin E2 which down regulated CD23 membrane expression and IgE secretion. Such data showed that antibiotics were able to interfere with cytokine cascade which controlled the immunoglobulin isotype.

B-Lymphocytes↗
PubMed1992

T cell receptor gamma variable gene locus polymorphism in patients with rheumatoid arthritis.

OBJECTIVE: We sought new susceptibility markers for rheumatoid arthritis (RA) among the T cell receptor gamma (TCR gamma) genes. METHODS: We analyzed restriction fragment length polymorphisms (RFLP) of the first variable subgroup of TCR gamma genes in a group of French control subjects and a group of French RA patients. RESULTS: No significant difference in Eco RI RFLP was found between the 2 study populations: Allele frequencies were virtually identical. There was no polymorphism using Hind III. CONCLUSION: These results exclude TCRV gamma I polymorphism as a disease susceptibility marker in RA.

Arthritis, Rheumatoid↗
PubMed1992

Generic HLA-DRB1 gene oligotyping by a nonradioactive reverse dot-blot methodology.

HLA-DRB1 allelic specificities can be determined using SSOs annealing to their complementary PCR-amplified target DNA. To perform HLA-DR oligotyping routinely for donors and recipients of bone marrow transplantation, a "reverse" dot-blot technique has been developed that consists in the hybridization of labeled PCR-amplified target DNA to SSOs that have been first attached to nitrocellulose membranes. The 15 oligonucleotides chosen enabled the following HLA-DRB1 "generic" specificities to be defined: DR1, BON, 2, 3, 4, 11, 11 JVM, 12, 13, 13 HAG, 14, 7, 8, 9, 10. The genomic DNA was amplified by asymetric PCR with incorporation of biotinylated deoxynucleotides predominantly to generate labeled single-stranded DNA. Hybridization between specific immobilized oligoprobes and target DNA was nonradioactively detected by a colorimetric reaction using alkaline phosphatase. The reverse dot-blot methodology was successfully tested, first, for the determination of HLA-DR4 subspecificities, and then the procedure was routinely applied to the generic HLA-DR oligotyping of bone-marrow donors and recipients.

Base Sequence↗
PubMed1991

Description of a polymorphism in the regulatory region of the HLA-DRA gene.

It was previously reported that the cell membrane expression of HLA class II molecules is tissue specific and variable among individuals. This variation could be explained at the level of gene regulation. Due to the fact that a coordinate regulation of the HLA-DR genes seems to exist, we focused on the HLA-DRA monomorphic gene. In order to study the polymorphism of the HLA-DRA gene regulatory region, we used restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified genomic DNA. The DdeI and PvuII digestions of the amplified DNA permitted the definition of the two alleles according to the absence (allele A) or the presence (allele B) of the two polymorphic restriction sites. The presence of these sites was confirmed by direct sequencing after PCR. Using homozygous typing cells, a close relationship between the HLA-DRB coding region and the HLA-DRA regulatory region polymorphisms was shown. Furthermore, a linkage between the HLA-DRA regulatory region and DRB3 gene coding region polymorphisms could be established. These results suggested a structural argument for different levels of HLA class II genes and, consequently, of cell-surface expression of class II antigens according to the allelic specificities of DRA, DRB1, and DRB3.

Alleles↗
PubMed1991

Treatment of infantile spasms with intravenous gamma-globulins.

In a prospective study, 23 children with infantile spasms received intravenous gammaglobulins in high doses. 19 patients present a West syndrome. 4 older patients were included in the study because infantile spasms had preceded their Lennox-Gastaut syndrome. None of the patients had recently undergone corticosteroid therapy. No effect was observed in 15 patients, while transitory clinical and/or electroencephalographic improvement was noted in 3. Complete normalization was obtained in the remaining 5 patients, of whom 4 had severe brain lesions. No correlation existed between the therapeutic results and immunological abnormalities, a deficiency in IgG subclasses in particular. On the whole, the therapeutic results were disappointing. But the existence of some cases in which spectacular electroencephalographic and/or clinical improvement was obtained leads us to suggest that IV gamma-globulins be used as auxiliary treatment in infantile spasms.

Electroencephalography↗
PubMed1990

Effect in vitro of a bacterial extract (OM-89) on interleukin 1 and interleukin 2 production by peripheral blood mononuclear cells from healthy subjects and rheumatoid arthritis patients.

The effect of a lyophilized extract from Escherichia coli strains (OM-89) on interleukin 1 and interleukin 2 production was studied by using peripheral blood mononuclear cells (PBMC) from healthy volunteers and from patients suffering from rheumatoid arthritis (RA) since, in this autoimmune disease, an abnormal cytokine network has been already described. The secretion of interleukin 1 (IL-1) was investigated in supernatants of monocytes purified by adherence, and measured by the C3H/HeJ thymocyte co-mitogenic assay. OM-89 was able to induce the secretion of IL-1 by normal and RA monocytes to about half of the level reached when the same cells were stimulated by lipopolysaccharide. The production of interleukin 2 (IL-2) was investigated in supernatants of PBMC, stimulated or not by phytohaemagglutinin (PHA) and mixed or not with various concentrations of OM-89. The level of IL-2 in supernatants, as measured by the stimulation of the CTLL2 murine cell line, was lower in RA supernatants than in control ones. In the presence of PHA and OM-89, the IL-2 production was enhanced and normalized in supernatants from RA patients. Such data may help to explain the clinical improvement previously reported in RA patients orally treated with OM-89.

Adjuvants, Immunologic↗
PubMed1990

Interleukin-1 release by alveolar macrophages in asthmatic patients and healthy subjects.

A thymocyte proliferative response assay was used to compare spontaneous and lipopolysaccharide (LPS)-induced interleukin-1 (IL-1) release by alveolar macrophage (AM) in asthmatic patients and normal subjects. Twelve asthmatic patients and seven nonsmoking healthy subjects underwent a bronchoalveolar lavage (BAL). All asthmatic patients had a reversible airway obstruction and 7/12 were allergic. BAL AM were separated by adherence on tissue culture plates in medium RPMI-1640 supplemented with antibiotics and fetal calf serum, and were incubated with or without 10 micrograms/ml LPS for 20 h. Free-cell supernatants were tested by C3H/HeJ mice thymocyte proliferative assay. Unstimulated AM supernatant IL-1 activity was significantly higher in asthmatic patients (mean +/- SEM: 47.8 +/- 11.9 units/10(6) AM) in comparison with healthy subjects (4.8 +/- 2.3 units/10(6) AM; p less than 0.05, Mann-Whitney U test) but did not significantly differ between allergic (42.2 +/- 15.5 units/10(6) AM) and intrinsic asthmatic patients (55.8 +/- 20.7 units/10(6) AM). For healthy subjects, IL-1 activity was significantly higher in LPS-stimulated AM supernatants (85 +/- 20 units/10(6) AM, p less than 0.05; Mann-Whitney U test) in comparison with unstimulated ones; for asthmatic patients, unstimulated and LPS-stimulated AM supernatant IL-1 activity did not significantly differ. This finding is in accordance with previous work suggesting that AM from asthmatic patients have a weak suppressive activity upon lymphocyte proliferation and emphasize the enhanced AM releasability in asthma.

Adolescent↗
PubMed1990

Anti-F(ab')2 antibody response to the injection of anticlass II HLA alloantibodies in patients with rheumatoid arthritis.

Placenta eluted gamma globulins (PEGG) contain antibodies against class II HLA antigens and have been used for treating patients with rheumatoid arthritis (RA). In view of the potential use of antibodies to class II HLA for treating autoimmune diseases we looked for the immunobiological effects of PEGG injections in patients. No modulation of class II HLA was seen at the surface of circulating mononuclear cells after one week of daily PEGG injections. In some patients, antibodies to F(ab')2 fragments of PEGG-IgG were produced. These antibodies reacted against F(ab')2 of any IgG as well and did not prevent anticlass II HLA antibodies from binding to class II HLA, thus showing no characteristics of classical antiidiotypic antibodies. The appearance of anti-F(ab')2 antibodies was not correlated with the clinical course of the disease. Their significance is discussed.

Animals↗
PubMed1990

[Alteration of IgE production by cefadroxil].

The effect of two cephalosporins, cefadroxil and cefalexine, was in vitro studied by using two models of regulation of the IgE production in healthy humans, e.g. the induction of CD23-antigens on B-cells and the IgE synthesis in cell culture supernatants after stimulation by recombinant interleukin-4. Cefadroxil clearly inhibited CD23 membrane expression on normal human B-lymphocytes. In the same way, this cephalosporin blocked up to 90% of the in vitro interleukin-4-dependent IgE production by normal peripheral blood mononuclear cells. Cefalexine was unable to do the same. There results suggest that cefadroxil interplays with the regulation processes of the IgE production in humans.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

A method of HLA class II typing using nonradioactive labelled oligonucleotides.

The typing of HLA class II genes using molecular biology techniques has brought undoubtedly new insights in the analysis of their polymorphism. Particularly interesting is the dot-blot analysis of enzymatically-amplified genomic DNA hybridized with sequence-specific oligonucleotides. In order to use this technique of typing on a routine basis, we established a non-radioactive detection method of enzymatically-amplified genomic DNA dot-blots. We could clearly demonstrate that, using biotin-labelled specific oligonucleotides, it was possible to specifically discriminate between DQB1 first domain DNA sequences displaying three, two or even only one base-pair difference at a given codon position. The very satisfactory sensitivity level reached by this non-radioactive detection method could safely allow its use for clinical applications of HLA typing at the DNA level.

DNA↗
PubMed1988

Increase of class II HLA molecules on the membrane of B lymphocytes from patients with rheumatoid arthritis.

Using a novel cytofluorometric method of cellular antigen quantification, we examined peripheral blood mononuclear cells (PBMC) from patients suffering from rheumatoid arthritis (RA) for quantitative modification of class II human leucocyte antigen (HLA) molecules expressed on the surface. Class II HLA molecules were detected by indirect immunofluorescence with a monomorphic monoclonal antibody. No change was observed in the density of class II HLA molecules at the surface of monocytes of RA patients as compared to that of paired healthy subjects. We confirmed that the percentage of class II HLA-bearing T cells was slightly increased in RA patients versus controls, but the density of class II antigens per cell could not be determined accurately. An increase in the density of class II HLA molecules on RA B cells was shown, suggesting that a chronic activation stage of this population contributes to the disease.

Antigens, Surface↗
PubMed1987

[Treatment of rheumatoid arthritis. Comparative study of the effect of immunoglobulins G eluted from the placenta and of venoglobulins].

A double-blind multicenter study comparing the effect of placenta eluted IgG and venoglobulins in the treatment of rheumatoid arthritis was conducted in 113 hospitalized patients. Rheumatoid arthritis was severe, classical (92 cases) or definite (21 cases), seropositive in 87 cases, with nodules in 32 cases; the mean duration of the disease was 10 years. The majority of patients had previously received numerous slow-acting drugs without result or with side-effects. A statistically significant decrease of all the quantitative indices but one (grip strength) was obtained with both products on the 8th day of treatment; the effect of placenta eluted IgG was statistically superior for the number of swollen joints (P less than 0.025), Ritchie's index (P less than 0.0005) and some extra-articular manifestations. There was no significant decrease in associated treatments and biological parameters (erythrocyte sedimentation rate, rheumatoid factor). Tolerance was excellent; some cases of benign venulitis were observed; treatment was never discontinued on account of side-effects. Further placebo-controlled of each of these immunoglobulins of placental origin are needed for firm conclusions to be drawn.

Arthritis, Rheumatoid↗