Specificity of natural serum antibodies present in phylogenetically distinct fish species.

B6 mice heterozygous at the lpr locus (B6 +/lpr and B6 lpr/+) were compared with lpr homozygous mice (B6 lpr/lpr) and control mice (B6 +/+) for levels of serum immunoglobulin (Ig), presence of autoantibodies and rate of B-cell membrane immunoglobulin (mIg) capping. The total serum Ig levels in B6 +/lpr and B6 lpr/+ mice remained much below the high titres found in B6 lpr/lpr mice, and were close to the titres found in B6 +/+ mice. However, the presence of anti-single-stranded (ss) DNA antibodies and of anti-nuclear antibodies (ANA) was detected in most B6 +/lpr and B6 lpr/+ mice, although less frequently and in lower titres than in B6 lpr/lpr mice. The rate of mIg capping was higher in B6 +/lpr and B6 lpr/+ mice than in B6 +/+ mice, but the acceleration of the capping process remained inferior to the one found in B6 lpr/lpr mice. Therefore, the lpr locus is not totally recessive: some B-cell hyperactivity is expressed in the heterozygous state. This is in contrast with its lack of expression at the level of lympho-proliferation of the lpr-characteristic T-cell subset: none of the lpr heterozygous B6 mice displayed detectable lymphadenopathy.     

Screening for Predictors of Chronic Ciguatera Poisoning: An Exploratory Analysis among Hospitalized Cases from French Polynesia

Ciguatera poisoning is a globally occurring seafood disease caused by the ingestion of marine products contaminated with dinoflagellate produced neurotoxins. Persistent forms of ciguatera, which prove to be highly debilitating, are poorly studied and represent a significant medical issue. The present study aims to better understand chronic ciguatera manifestations and identify potential predictive factors for their duration. Medical files of 49 patients were analyzed, and the post-hospitalization evolution of the disease assessed through a follow-up questionnaire. A rigorous logistic lasso regression model was applied to select significant predictors from a list of 37 patient characteristics potentially predictive of having chronic symptoms. Missing data were handled by complete case analysis, and a survival analysis was implemented. All models used standardized variables, and multiple comparisons in the survival analyses were handled by Bonferroni correction. Among all studied variables, five significant predictors of having symptoms lasting ≥3 months were identified: age, tobacco consumption, acute bradycardia, laboratory measures of urea, and neutrophils. This exploratory, hypothesis-generating study contributes to the development of ciguatera epidemiology by narrowing the list from 37 possible predictors to a list of five predictors that seem worth further investigation as candidate risk factors in more targeted studies of ciguatera symptom duration.     

Presence of natural autoantibodies in hyperimmunized mice.

Mice were immunized with various antigens in complete Freund's adjuvant following various injection schedules. Hybridomas were produced from the spleens of these immunized mice and examined for production of antibodies directed against the antigen injected and against a panel of self (tubulin, actin, myosin, DNA) and non-self antigens (myoglobin, spectrin, peroxidase, trinitrobenzene). Two to five percent of the hybrids were found to secrete polyspecific antibodies able to react with two or more antigens of the panel. Several of these hybrids were subcloned and expanded into ascites. The monoclonal immunoglobulins they secreted were isolated and shown to be IgM (kappa) and to possess the polyspecific antibody function. Several hybrids were also found to secrete antibodies reacting with the immunizing antigen as well as one or more antigens of the panel. The antibody secreted by one subclone which reacts with both the immunizing antigen, prolactin and one of the panel antigens, TNP, has been isolated using a DNP-immunoadsorbent. The isolated antibody was found to be a monoclonal IgM (kappa) immunoglobulin and to react both with prolactin and TNP. The hypothesis is advanced that cells carrying polyspecific natural antibodies as receptors after a given antigenic stimulation proliferate into cells producing highly specific antibodies for epitopes of that given antigen; the cells with polyspecific receptors will be continuously replaced by new cells probably on bone-marrow origin.     

Expression, immunochemical characterization and localization of the Mycobacterium tuberculosis protein p27

Rv2108 is a gene of the PPE family of Mycobacterium tuberculosis specific for this bacterial complex and that may encode a putative protein p27. This gene was amplified, inserted into bacterial vectors, sequenced, and expressed as a recombinant protein. Specific antibodies to this protein were generated and used for immunochemical characterization and cellular localization. Mass spectrometric analysis of the expressed protein revealed a molecule that corresponded to the p27 putative protein. The expressed protein was immunologically active, and reacted with antibodies from tuberculosis patient sera. Specific immunoblot analysis confirmed the presence of the p27 antigen in Mycobacterium bovis BCG strain and in human clinical isolates of M. tuberculosis, but not in other mycobacteria tested. Western blot and immunoelectron microscopic analysis of BCG strain indicated that the p27 protein is localized in the membrane of the cell. The specific expression of the p27 protein in the M. tuberculosis complex could provide a novel specific complimentary diagnostic test for the presence of and infection with M. tuberculosis.     

Les torsions sur testicules cryptorchides

Purpose:

Cryptorchidism is a rather frequent pathology in urology. It is associated with a high risk of infertility and degeneration. It also seems to be associated with a high risk of torsion. This entity is poorly studied in the literature. We studied the cases of torsion on cryptorchid testicles hospitalized at our service, to better characterize this pathology and reduce the rate of orchidectomy.

Methods:

We underwent a retrospective study of all the cases of torsion on a cryptorchid testicle hospitalized in our service of urology between 1999 and 2007.

Results:

The age of patients was between 7 months and 39 years. Torsion touched the right testicle in 53% of the cases. Patients experienced a brutal pain of the inguinal area with an under cutaneous mass inflammatory and a painful and empty homolateral scrotum. In 60% of the cases, the diagnosis was late and an orchidectomy was carried out. In the other cases, a lowering of the testicle was done with the controlateral orchidopexy.

Conclusion:

Even though torsions on a cryptorchid testicle are rare, we should not ignore them. The early diagnosis will make it possible to save and lower the testicle, and track a possible degeneration.     

Cellular distribution of a mixed MHC class II heterodimer between DRalpha and a chimeric DObeta chain

Human MHC class II antigens include HLA-DR, -DQ, and -DP molecules that present antigens to CD4+ T cells, as well as the non-classical molecules HLA-DM and -DO. HLA-DM promotes peptide binding to class II molecules in endocytic compartments and HLA-DO, which is physically associated with HLA-DM in B lymphocytes, regulates HLA-DM function. Antibodies specific for the DObeta chain were obtained by immunization of mice with a heterodimer consisting of a chimeric DObeta chain (DR/DObeta), containing 18 N-terminal residues of DRbeta, paired with the DRalpha chain and isolated from transfected murine fibroblasts. The specificity of this serum for the DObeta chain and the lysosomal expression of the HLA-DO protein was confirmed using mutant human B cell lines lacking DR or DO molecules. The lysosomal localization of HLA-DO in human B cells contrasts with the cell surface expression of the mixed pair in transfected murine fibroblasts and raises questions concerning the role of the putative targeting motifs in HLA-DO. Transfection of the chimeric DR/DObeta chain along with DRalpha into human epithelial HeLa cells resulted in high levels of expression of the mixed isotypic pair at the surface of transfectants as well as in lysosomes. The same pattern was observed in HeLa cells transfected with the DObeta chimera and a DRa chain lacking the cytoplasmic tail. Taken together, these results suggest that functional sorting motifs exist in the DObeta chain but that the tight compartmentalization of HLA-DO observed inside B lymphocytes is controlled by the HLA-DOalpha chain and HLA-DM.     

Specific and natural antibody production during Salmonella typhimurium infection in genetically susceptible and resistant mice.

Genetically susceptible (C57BL/6) and resistant (CBA) mice were infected with an avirulent strain of Salmonella typhimurium and studied over a 35-day period for the production of antibodies directed against bacterial antigens including lipopolysaccharide (LPS) (specific antibodies) and antibodies directed against self antigens [natural antibodies (NAb)]. Antibodies directed against LPS and self antigens were detected by enzyme immunoassay (EIA) and those directed against other bacterial antigens by immunoblotting. We found that serum natural antibody titres in C57BL/6 and CBA mice were similar and correlated with the bacterial load in the spleen and liver. In C57BL/6 mice, anti-LPS antibodies remained polyreactive and of the IgM isotype. In contrast, CBA mice, after an early increase in polyreactive IgM anti-LPS antibodies, mounted a specific anti-LPS IgG antibody response. The immunoblotting results demonstrated that the IgM polyreactive antibodies in the resistant and susceptible mice recognized bacterial antigens of different molecular weights and that CBA, but not C57BL/6 mice, were able to produce IgG antibodies recognizing bacterial components. Our results suggest that the synthesis of antibodies directed against bacterial antigens and natural antibodies follow, at least partially, distinct pathways, but they do not allow us to determine whether these two antibody populations are produced by the same or distinct B-cell subpopulations.