Search PubMed⌕ Search

Biomedical subjects

J P Bouvet

Publications and source records attributed to J P Bouvet.

At least 19 recordsLinked to original sources
PubMed2005

Silent antibodies.

Over the past years, progress has been made in understanding B cells and antibody recognition functions, particularly in the context of autoimmune diseases. In addition to the existence of "natural antibodies", recent studies suggest the existence of immunoglobulins with no apparent specificity that may acquire polyreactivity following a mild denaturation in inflammatory sites. They are called "silent antibodies". Together with related observations on B cell development, selection and signaling, the recent insights are providing clues into our understanding of autoimmunity.

Antibody Specificity↗
PubMed2002

Fibre remote optoelectronic gamma dosimetry based on optically stimulated luminescence of Al2O3:C.

Optically stimulated luminescence dosimetry (OSL-D) used in conjunction with fibre optics enables a remote measurement of dose, for the purpose of radioprotection in the nuclear industry and in medicine (radiology, radiotherapy). Alumina OSL crystals are used because of their low Z, low fading and optical transparency, which improves the sensitivity. An optoelectronic portable dosemeter has been designed and tested that shows a dose detection of 50 microGy with a 20 metre-long fibre. Following irradiation, all trapped electrons are released under light stimulation while the OSL is integrated to provide dose-equivalent measurements. A compensation technique is designed with the help of the MCNP4b code, so that both angular and photon energy characteristics comply with international standards (CEI 61066) for photon dose equivalent Hp(10). Two sensors are described that allow measurements over a wide solid angle (95% of 4piSr), for photon energies ranging from 15 keV to 3 MeV.

Aluminum Oxide↗
PubMed2001

Induction of natural autoantibody activity following treatment of human immunoglobulin with dissociating agents.

Treatment of normal polyclonal human IgG and of F(ab')2 fragments of IgG with 6.0 M urea, 1.3 M sodium thiocyanate or with acidic buffers (pH 2.0), resulted in a dramatic and selective enhancement of the preexisting antibody reactivity with self antigens. Enhanced antibody activity revealed by the dissociating agents was inhibited by the addition of an excess of the relevant soluble antigen. Human monoclonal IgG, including four different IgG1m(1) V(H)3+ and V(K)3+ paraproteins differing only in their CDRs, exhibited different changes in reactivity following urea treatment indicating major involvement of CDR sequences. The calculated dissociation constant of the binding reaction of normal IgG to the self antigen actin was 10(-6) M, whether IgG had been treated or not, indicating that the treatment increased the proportion of available self-reactive molecules instead of increasing the affinity of the preexisting natural autoantibodies. Enhanced autoreactivity was not due to aggregation of Ig, unmasking of the antibody site by removal of low MW antigens, nor to the denaturation of natural Id-anti-Id complexes. Taken together, these results suggest that treatment of Ig with dissociating agent results in the exposure of basic polyreactive antibody structures. The enhancement of reactivity may be of relevance in physiology of mucosal immunity and in therapeutic immunomodulation.

Actins↗
PubMed2001

Different dysregulations of the natural antibody repertoire in treated and untreated HIV-1 patients.

To investigate a possible dysregulation of the autoantibody network in AIDS patients, the relative activity of representative natural antibodies was measured in serum IgG and IgM. These immunoglobulins were purified from two cohorts of 20 HIV-infected patients undergoing, or not, a triple combination therapy. A cohort of 20 normal patients was used as a control. Marked alterations of the natural antibody repertoire were observed, varying according to the isotype and specificity of the antibody studied. For the classical self-protein antigens, human actin and myosin, the changes observed in the untreated cohort were absent in the treated cohort. In contrast, no changes, or even increased changes of the activity of antibodies to special antigens, DNA and TNP, occurred in the treated cohort. The differences were highly significant, indicating that this repertoire is regulated and not randomly modified by the disease. These results suggest the presence of different factors of dysregulation of the B cell repertoire of natural antibodies associated with the disease as well as with the treatment. These major dysregulations may favor the autoimmune phenomena observed during HIV infection.

Actins↗
PubMed2001

Induction in mucosa of IgG and IgA antibodies against parenterally administered soluble immunogens.

The induction of a mucosal immunity provides an additional principle of vaccination by preventing the entry of pathogens in the body. Albeit the fact that intensive research has been conducted on local vaccines, the major mucosal vaccine commercially available for human use remains the oral polio vaccine. We have previously demonstrated that parenteral vaccination in humans with tetanus toxoid (TT) results in a genital immunoglobulin (Ig)G antibody (Ab) response. Here, we show that injections of TT with no adjuvant induces an anti-TT response in the mucosal tissues of normal BALB/c mice. The response is multiregional, involves both IgG and IgA isotypes, and is long-lasting. Similarly, injections of haptens coupled to TT or to other diffusible proteins may induce mucosal Abs. These results led us to immunize normal BALB/c mice with a viral peptide coupled to TT by disulfide bridging. The hapten was a 17 amino acid peptide containing the ELDKWA sequence of human immunodeficiency virus (HIV)-1 gp41. A significant IgG and IgA Ab response to the immunizing peptide was induced in various mucosal tissues despite the presence of a suboptimal Ab response in the spleen. The results indicate that mucosal immunity to peptides that are candidates for human vaccinations may be achieved by parenteral adjuvant-free immunization with peptide coupled to TT.

Amino Acid Sequence↗
PubMed2001

[Properties of mucosal antibodies].

Mucosal antibodies consist of a variety of molecules, including secretory IgA and local IgG, involved in the first immune barrier of defence against pathogens. They account for the majority of daily synthesized immunoglobulins in the body and mostly depend on the secretory immune system which is independent from its systemic counterpart. Acting by immune exclusion and immune elimination, these immunoglobulins correspond to preimmune poly-reactive natural antibodies and to antigen-induced antibodies. Recent progress in this field have suggested new approaches of mucosal vaccines preventing the entry of pathogens in the body.

Animals↗
PubMed2000

An ELISA method to measure total and specific human secretory IgA subclasses based on selective degradation by IgA1-protease.

We have taken advantage of the property of IgA1-proteases to selectively cleave the human IgA1 subclass into Fabalpha and Fcalpha-J chain-secretory component (Fcalpha-J-SC) fragments in order to design a novel ELISA method for measuring the two secretory IgA (S-IgA) subclasses in secretions. The assay is based on the loss of detection of S-IgA1 by a combination of peroxidase-labelled antibodies to secretory component and Fab following IgA1-protease treatment. The specificity is that of the protease and the sensitivity of the detection is 5 ng/ml. Moreover, the use of purified S-IgA1 and S-IgA2 controls is not necessary. The assay has been successfully applied to the analysis of colostral S-IgA antibodies (Abs) to HIV-1-gp160 from HIV-1 positive women. The major subclass of colostral S-IgA antibodies to gp160 was found to be of the alpha1 isotype but the specific activity of anti-HIV-gp160 S-IgA2 was, however, higher than that of S-IgA1.

Adult↗
PubMed2000

Can isotype switch modulate antigen-binding affinity and influence clonal selection?

Four different monoclonal Ig (MIg) (IgA1kappa, IgG1kappa, IgG2kappa and IgG4kappa) displaying anti-tubulin activity were detected in the serum from a lymphoma patient. The complete sequence of three of these MIg showed identical V(H) and V(L) domains and the presence of mutations compatible with an antigen-driven process. Surprisingly, despite complete homology in their variable domains, IgA1kappa, IgG1kappa, or their Fab fragments bound to a common motif recognized in beta tubulin, with significant differences in affinity (IgA1kappa 1.52x10(-8) M, and IgG1kappa 2.09x10(-7) M). To substantiate these results, the V(H) and V(L) domains from IgA1kappa were cloned and introduced into expression vectors containing the constant kappa exon and either the mu or the gamma1 constant exon, and complete recombinant IgMkappa and IgG1kappa were obtained. Like the IgA1kappa, the IgMkappa construction bound to the tubulin epitope with consistent affinity (7.7x10(-9) M), whereas the IgG1kappa construction displayed a significantly lower affinity (3.28x10(-7) M). These results provide definitive evidence that isotype can influence binding affinity to antigen and suggest that malignant transformation occurred at the germinal center once the mutational process was achieved and the switch process was still active.

Amino Acid Sequence↗
PubMed2000

Bacterial immunoglobulin superantigen proteins A and L activate human heart mast cells by interacting with immunoglobulin E.

Human heart mast cells (HHMC) have been identified in heart tissue, perivascularly, and in the intima of coronary arteries. In vitro activation of isolated HHMC induces the release of vasoactive and proinflammatory mediators (histamine, tryptase, and cysteinyl leukotriene C(4) [LTC(4)]). We investigated the effects of several bacterial proteins on HHMC activation in vitro. HHMC released histamine, tryptase, and LTC(4) in response to Staphylococcus aureus Cowan 1 and the immunoglobulin (Ig)-binding protein A, but not to S. aureus Wood 46, which does not synthesize protein A. The effect of protein A was inhibited by preincubation with monoclonal IgM V(H)3(+). Some strains of Peptostreptococcus magnus express an Ig light chain-binding surface protein called protein L. Such bacteria and soluble protein L stimulated the release of preformed and newly synthesized mediators from HHMC. Preincubation of HHMC with either protein A or protein L resulted in complete cross-desensitization to a subsequent challenge with the heterologous stimulus or anti-IgE. Monoclonal IgE (kappa chains) blocked protein L-induced release, whereas IgE (lambda chains) had no effect. Streptococcal protein G, formyl-containing tripeptide, and pepstatin A did not activate HHMC. Bacterial products protein A and protein L and intact bacteria (S. aureus and P. magnus) activate HHMC by acting as Ig superantigens.

Adult↗
PubMed1999

Immunoglobulins of the human amniotic fluid.

PROBLEM: Except for the description of a secretory immunoglobulin (S-Ig) of a low size, no recent study has investigated the molecular status of antibodies in the human amniotic fluid. METHOD: After separation with a high performance chromatography, we analyzed the different isotypes of amniotic Igs by immunoblotting and ELISA. RESULTS: IgG is found to be the major isotype and to contain mother-derived tetanus antitoxins. IgA is much less abundant, whereas no IgM can be detected. IgA is monomeric, with a low level of secretory IgA and with various amounts of free secretory component (SC). The presence of a low level of SC-containing immunoglobulin of a low size is confirmed during the last trimester of pregnancy. This molecule contains no alpha chain but includes a Fabgamma fragment noncovalently associated with SC. IgG, IgA, and SC are detected in the fetal urine and, therefore, can reach the amniotic fluid by this route. CONCLUSION: In addition to the predominant maternal IgG, the amniotic fluid contains different molecular forms of fetal immunoglobulins. Their function as an immune barrier against infection and against mother-derived autoantibodies is discussed.

Amniotic Fluid↗
PubMed1998

Endogenous superallergen protein Fv induces IL-4 secretion from human Fc epsilon RI+ cells through interaction with the VH3 region of IgE.

We investigated the mechanism whereby protein Fv (pFv), a human sialoprotein found in normal liver and largely released in the intestinal tract in patients with viral hepatitis, induces mediator release from basophils and mast cells and evaluated whether it also induces IL-4 synthesis and secretion in basophils. pFv is a potent stimulus for histamine and IL-4 release from purified basophils. Histamine and IL-4 secretion from basophils activated by pFv was significantly correlated (rs = 0.70; p < 0.001). There was also a correlation (rs = 0.58; p < 0.01) between the maximum pFv- and anti-IgE-induced IL-4 release from basophils. The average t1/2 for pFv-induced histamine release was lower (3.5+/-1.5 min) than for IL-4 release (79.5+/-8.5 min; p < 0.01). IL-4 mRNA, constitutively present in basophils, was increased after stimulation by pFv and was inhibited by cyclosporin A and tacrolimus. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released IL-4 in response to pFv and anti-IgE. The response to an mAb cross-linking the alpha-chain of Fc epsilon RI was unaffected by this treatment. Three human VH3+ monoclonal IgM concentration-dependently inhibited pFv-induced secretion of IL-4 and histamine from basophils and of histamine from human lung mast cells. In contrast, VH6+ monoclonal IgM did not inhibit the release of IL-4 and histamine induced by pFv. These results indicate that pFv, which acts as an endogenous superallergen, interacts with the VH3 domain of IgE to induce the synthesis and release of IL-4 from human Fc epsilon RI+ cells.

Adult↗
PubMed1998

Human amniotic IgA inhibits natural IgG autoantibodies of maternal or unrelated origin.

We show that the natural autoantibody activity of amniotic IgG dramatically increases after purification, and that the IgG-depleted fraction can suppress the activity of IgG natural antibodies from amniotic fluid or from the maternal serum. This suppression is also observed towards serum IgG from unrelated adults but does not impair the tetanus antitoxin activity of serum-derived IgG. Absorption experiments and immunoglobulin separation by gel permeation demonstrate that this suppression is due to monomeric immunoglobulins of the IgA isotype. The inhibition is associated with an anti-F(ab')2 activity of the amniotic IgA, involving hypervariable regions of the IgG as demonstrated by different reactivities towards monoclonal IgG sharing the same family of VH and Vkappa domains. These results indicate that the inhibition of natural autoantibodies not only occurs with fetal and adult serum IgM, as reported by other groups, but also with amniotic IgA, suggesting a general and important phenomenon. In the case of the amniotic fluid, IgA could protect the fetus against maternal IgG autoantibodies without interfering with simultaneously translocated antigen-induced IgG antibodies to pathogens.

Adult↗
PubMed1998

Release of the soluble co-receptor (protein Fv) of secretory immunoglobulins after colonization of axenic rats by the human gut microflora.

The presence of protein Fv (pFv), a soluble co-receptor of human gut antibodies, was investigated in heteroxenic rats as a function of the presence of the human digestive microflora. This endogenous molecule was not detected in the stools of axenic rats but was found in those of heteroxenic animals. The release was delayed for 1 week after colonization and found to be independent from the kinetics of bacteria-induced short-chain fatty acids issued from the catabolism of carbohydrates and of proteins. The similar bacterial composition of pFv-positive and of pFv-negative stools, and the lack of induction by different dominant bacterial genera, suggest that non-dominant species must be involved. These results indicate that human colonic flora is a major inducer of pFv and thus participates in increasing the efficiency of the intestinal immunity by this additional mechanism known to maintain and augment the polymeric status of secretory immunoglobulin (Ig)A.

Animals↗