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Biomedical subjects

I Dorval

Publications and source records attributed to I Dorval.

At least 19 recordsLinked to original sources
PubMed1995

Contribution of p56lck to the upregulation of cytokine production and T cell proliferation by IL-2 in human CD3-stimulated T cell clones.

Interaction of the interleukin 2 receptor (IL-2R) beta chain with the lymphocyte-specific protein tyrosine kinase (PTK), p56lck, has led to the speculation that p56lck participates in growth signal transduction. Although activation of T cells with interleukin 2 (IL-2) results in the activation of p56lck, accumulating data support the notion that Lck does not play an essential role in mitogenic signal delivery from the IL-2R. Since this src-related PTK has been shown to enhance TCR/CD3-mediated T cell responsiveness, here we investigated whether activation of Lck by IL-2 could contribute to enhance TCR/CD3-mediated T cell functions. This was achieved by using human CD4(+)-cloned T cells and comparing the effects of IL-2 on p56lck kinase activation and cytokine production. Results show that p56lck kinase activity increased as early as 1 min, reached a maximum within 5 min and decreased within 60 min after IL-2 stimulation. Such treatment with IL-2 also resulted in enhancing T cell responsiveness to CD3+PMA stimulation, as assessed by IL-2 and IFN-gamma secretion and by T cell proliferation. This increase of T cell functions was correlated with IL-2-induced p56lck activation in both dose-response and time-course experiments. Taken together these results strongly suggest that activation of Lck by IL-2 may play a role in regulating CD3-mediated T cell functions.

CD3 Complex↗
PubMed1995

Obstructive azoospermia with agenesis of vas deferens or with bronchiectasia (Young's syndrome): a genetic approach.

Two groups of infertile men with obstructive azoospermia were screened for cystic fibrosis (CF) gene mutations (delta F508, exons 3, 4, 7, 10, 11, 14a, 17b, 19, 20, 21). The first group was composed of 26 patients with congenital agenesis of vas deferens (CAVD). The second group was composed of 12 patients with obstructive azoospermia associated with chronic suppurating respiratory disease (Young's syndrome). Of the group with CAVD, 77% of patients showed at least one mutation in the CF transmembrane conductance regulator (CFTR) gene. The delta F508 mutation occurred most frequently (54%), and the second most frequent mutation to occur was R117H (27%). Six patients were double heterozygotes. In Young's syndrome, no CF mutations were detected. CAVD can be considered as an incomplete clinical form of CF. However, the differences observed in CF mutations between CF and CAVD suggest that they are different disorders resulting from mutations in the same gene. Young's syndrome is a very different clinical entity.

Adult↗
PubMed1995

Preferential usage of the T-cell receptor by influenza virus hemagglutinin-specific human CD4+ T lymphocytes: in vitro life span of clonotypic T cells.

Human helper T-cell (Th) responses to influenza A virus were studied by analyzing T-cell receptor V beta gene diversity in hemagglutinin-specific Th lymphocytes. The T-lymphocyte population from peripheral blood became quickly oligoclonal when stimulated in vitro with the HA306-329 peptide, and T-cell receptor V beta 3 genes were mainly expanded. Moreover, specific junctional region oligonucleotide probes corresponding to hemagglutinin-specific clones were used to estimate temporal diversity during antigenic stimulations.

Amino Acid Sequence↗
PubMed1995

Structural analysis of CFTR gene in congenital bilateral absence of vas deferens.

Congenital bilateral absence of the vas deferens (CBAVD) is found in most males with cystic fibrosis (CF), but this malformation can be observed without any pulmonary or digestive features. We have analyzed 13 exons of the CF gene in a cohort of 25 CBAVD patients. Among the 50 chromosomes studied, 24 mutations were identified: delta F508 (14 cases), R117H (7 cases), R1070W (2 cases), 621 + 1 G --> T (1 case), and A1067V (1 case). Except for delta F508, the most frequent mutations (R117H, R1070W) were not observed in the CF group (109 patients) studied in our laboratory. We discuss the significance of these results.

Adult↗
PubMed1995

Proteases.

Proteases are enzymes which are widely distributed in cells and play a key role in protein metabolism. The aim of this paper is to review the classification and nomenclature of proteases, their catalytic mechanisms, the regulation of proteolytic activity and finally the major biological functions of proteases.

Animals↗
PubMed1994

Contribution of tyrosine kinases to the selective orientation of human CD4+ bifunctional cloned T cells toward proliferation or cytolytic function.

We show that T cell activation of human CD4+ cloned T cells through the CD2 molecule can induce either autocrine proliferation or cytolysis, depending on the pair of anti-CD2 mAbs used for stimulation, that is, D66/T11(1) or GT2/T11(1), respectively. As the earliest biochemical event after CD2 stimulation is likely the induction of tyrosine phosphorylation of various proteins, we investigated whether differential activation of protein tyrosine kinases (PTKs) could contribute to the selective induction of each function. Results show that herbimycin A, a potent PTK inhibitor, markedly decreased the induction of both proliferation and cytolysis. This implies a regulatory role for tyrosine phosphorylation in the induction of each function by CD2. However, that PTKs are differentially activated upon induction of proliferation by D66/T11(1) or cytotoxic function by GT2/T11(1) emanated from two different approaches. First, immunoblotting total cellular extracts with an anti-phosphotyrosine mAb showed different patterns of tyrosine phosphorylation depending on the pair of CD2 mAbs used for stimulation. Second, a differential activation of p56lck, a src-related PTK, was observed after stimulation with D66/T11, and GT2/T11(1). Although induction of proliferation by D66/T11(1) was correlated with increased Lck activity, this was not observed when cells were triggered to lyse by GT2/T11(1). Thus, by providing striking correlative evidences linking differences in PTK activation with induction of different functions in bifunctional cloned T cells, our results strongly suggest that PTKs may contribute to the selective orientation of T cell functions at a single-cell level.

Antibodies, Monoclonal↗
PubMed1994

Molecular basis for degenerate T-cell recognition of one peptide in the context of several DR molecules.

We report the study of one CD4+ T-cell clone that recognizes peptide HA306-320 in the context of autologous DR1101 molecules as well as of allogeneic DR1301, DR0402, DR1501, and DR1601 molecules. This degenerate T-cell recognition is mediated by a single T-cell receptor (TCR) as judged by both TCR-V beta sequencing and cold-target competition assays. Restriction analysis shows that substitutions of DR residues within the third hypervariable region result in a loss of T-cell reactivity, which is restored by additional substitutions in the first and/or second hypervariable regions. Thus, there is no correlation between antigen presentation abilities of the different allelic DR products and the degree of sequence homology between these products. DR residues whose substitution is compatible with T-cell recognition potentially interact with peptides rather than with TCRs by virtue of their location in the floor of the groove or as previously documented for residues of the alpha-helix. Furthermore, antigen presentation by allogeneic DR molecules occurs independently of their affinity for the peptide, as determined in cell surface-binding assays using biotinylated HA306-320. Altogether these data suggest that degenerate T-cell recognition mainly depends on an influence of polymorphic DR residues on the configuration adopted by the peptide in the DR groove so that the epitope is left intact.

Amino Acid Sequence↗
PubMed1993

Implication of HLA-DR residues at positions 67, 71, and 86 in interaction between HLA-DR11 and peptide HA306-320.

To get further insight into the role of three polymorphic DR residues located in one alpha-helix of the HLA-DR binding groove, we studied how natural substitutions at positions 67, 71, and 86 on DR11 molecules influence MHC binding and/or T cell recognition of peptide HA306-320 and of monosubstituted peptide analogues. Our results show that: 1) Reactivities of all HA306-320-specific T cell clones tested are decreased by DR substitution at position 86 and can even be lowered by additional substitutions at position 71, and at positions 71 plus 67, indicating that these three residues are functionally important. 2) The functional effects of substitutions at positions 67, 71, and/or 86 cannot be explained by a decreased affinity of HA306-320 for the substituted DR11 molecules, as determined in binding assays. 3) More likely, they are explained by modifications of the conformation, orientation, or location of the peptide once bound in the HLA groove, because each individual DR substitution at positions 86, 71, and 67 differentially affects the binding ability of the same panel of 50 monosubstituted analogues. 4) This interpretation is reinforced by the identification of a small set of monosubstituted analogues that can compensate the functional effects of DR substitutions at positions 86, 86 plus 71, or 86 plus 71 plus 67, and thus restore T cell reactivities. All together these results strongly suggest that residues 67, 71, and 86 play a key role in interactions with HA306-320, probably by modifying the way the peptide is bound within the binding groove of HLA-DR11. Using the same DR11.1-restricted clones, we identified putative T cell and DR contact residues of HA306-320 by comparing DR binding and T cell-activating capacity of the peptide analogues. This analysis suggests that: 1) Residues 310, 311, 312, 313, and 316 are putative TCR contacts. 2) Peptide HA306-320 anchors to DR11.1 molecules mainly via residue Y-309, possibly at the vicinity of DR residue 86, whereas peptide residues 315 and 317 constitute minor aggregotopes that would be at the vicinity of DR residues 71 and/or 67. 3) Finally, residues 308, 310, and 314 might also be on the MHC side of the DR-peptide-TCR complex.

Amino Acid Sequence↗
PubMed1993

Analysis of 160 CF chromosomes: detection of a novel mutation in exon 20.

The cystic fibrosis (CF) gene has been cloned and a major mutation identified (delta F508). This 3-bp deletion has been found in approximately 70% of CF chromosomes. We have used the strategy of denaturing gradient gel electrophoresis followed by direct sequencing of the polymerase chain reaction products, in order to detect other mutations in exons 10, 11 and 20 of the CF transmembrane conductance regulator gene. A new mutation, F1286-S, was found in exon 20. It involves a nucleotide change of T-->C at nucleotide 3989 and changes a phenylalanine into serine at position 1286 of the protein.

Adolescent↗
PubMed1993

Localization of seven new genes around the HLA-A locus.

A yeast artificial chromosome (YAC B30) with a 320 kb insert of genomic DNA which includes the HLA-A gene was used to screen a cDNA library of human duodenal mucosa. Seven cDNA clones were isolated which correspond to seven new non-HLA class I structural genes. These new genes are located within a region that may well contain the gene responsible for hemochromatosis and have therefore been named HCG I-VII (Hemochromatosis Candidate Gene). HCG I, III, V and VI are probably single copy genes, situated at 180, 155, 140 and 230 kb centromeric to HLA-A, respectively. HCG II, IV and VII present several copies: one copy of HCG II, one of HCG IV and one of HCG VII are centromeric to HLA-A (at 30, 70 and 100 kb respectively). Another copy of HCG IV is 20 kb telomeric to HLA-A. Each of the genes localized on the YAC B30 is associated with an CpG/HTF island.

Blotting, Southern↗
PubMed1993

[Molecular genetics of hemochromatosis].

Haemochromatosis is an inherited disorder of iron metabolism characterized by a general iron over loading. Without diagnosis and early treatment, it is a serious and potentially fatal disease by cardiac failure or hepatocellular carcinoma in particular. Gene prevalence was estimated at 0.06 in Brittany, so that haemochromatosis may be the most common genetic disease in this area. The biochemical defect of the disease is unknown; only one fact is well established: the iron absorption through duodenal mucosa is excessive. However we don't know if it is a primary event. The gene is also unknown but in 1975 it was located on the short arm of chromosome 6, closely linked to the HLA class I region, less than 1 cM from HLA-A. None of the genes coding for the known iron proteins could be the haemochromatosis gene because of their chromosomal localization. In order to locate this gene with precision, we have used a reverse genetic approach now called positional cloning. Characterization of new polymorphic markers and linkage disequilibrium analysis, have led us to locate the gene within a 350 kb region around HLA-A. We have then searched for all the structural genes in this region. Seven new genes have been so identified and located with precision. A structural analysis of these genes was undertaken to find an eventual abnormality in patients.

Hemochromatosis↗