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L Lebrun

Publications and source records attributed to L Lebrun.

49 records · Page 3Linked to original sources
PubMed1982

A critical study of the use of staphylococci containing protein A for separation of IgG and IgM antibodies.

This study was to determine the best conditions for using staphylococci bearing protein A to separate IgG from IgM. The validity of the technique was evaluated for detection of IgM with antimicrobial activity and for typing monoclonal IgM. The results indicate that separation of IgG and IgM is not entirely satisfactory in normal sera and worse in hyperglobulinemic sera. The detection and titration of IgM antimicrobial antibodies (rubella and hepatitis B core (HBc) specific IgM) was unreliable because IgG was only partially absorbed by staphylococcal cells, while a significant portion of IgM was bound. The use of higher concentrations of staphylococci did not improve the results because the more IgG was absorbed, the more IgM was also bound. It is shown that with anti-HBc specific IgM the risk of misinterpretation is very high with a sensitive radioimmunoassay technique allowing detection of trace amounts of nonabsorbed IgG. In contrast staphylococcal protein A proved useful in typing monoclonal IgM.

Animals↗
PubMed1982

An indirect immunofluorescence staining procedure for detection of human Fc gamma receptors on streptococci.

Fc gamma receptors on streptococci are usually revealed by hemagglutinating techniques (IgG coated red blood cells) or uptake of radiolabeled IgG. The results obtained with these methods are not always satisfactory. For this reason, we developed a technique involving indirect immunofluorescence staining. Bacterial smears were treated with human Fc gamma fragment and their binding to streptococcal Fc gamma receptors was revealed by a fluorescent F(ab')2 fragment of anti-human Fc gamma sheep antibodies purified on an IgG immunosorbent. These purified sheep F(ab')2 fragments did not contain any IgG nor Fc gamma as shown by SDS polyacrylamide gel electrophoresis. Under these conditions indirect immunofluorescence staining was a highly specific and sensitive method of detecting Fc gamma receptors on streptococci. Distribution of Fc gamma receptors was studied in 237 streptococcal strains of human origin belonging to groups A, B, C, D and G; these receptors were also looked for in 21 strains of alpha-hemolytic streptococci which did not possess the group carbohydrate and 12 strains of pneumococci. Fc gamma receptors were found only in group A, C and G streptococci, but all strains of these groups did not possess Fc gamma receptors.

Animals↗
PubMedDate not supplied

Significance of anti-IgG antibodies obtained by immunization of rabbits with some streptococcal strains.

Anti-human IgG antibodies have been found in a number of rabbit sera immunized with freshly isolated streptococci. The significance of these anti-IgG antibodies was investigated. An IgM rheumatoid factor was excluded because the antibodies to human IgG present in rabbit sera belonged to the IgG class and reacted with the different isotypes of the human 7 S IgG. No cross-reaction between streptococci and human IgG was found. The anti-IgG production could be attributed to the in vivo non-immunological binding of host IgG to the infecting streptococci, via their Fc(gamma) receptors. A strong adjuvant effect of streptococci for IgG was found, and it explained the noticeable induction of anti-IgG antibodies by trace amounts of immunogen bound to streptococci. The possible induction of anti-human IgG antibodies by streptococcal cells could be an alternative explanation of the numerous cross-reactions described between streptococci and different human tissues.

Animals↗
PubMedDate not supplied

[Presence of antibodies in human colostral secretory IgA against enteric commensal bacteria: biological implications (author's transl)].

Antisecretory component, anti-alpha, anti-mu and anti-Fc (gamma) fluorescent antibodies were used to detect the presence of immunoglobulins with antibody activity against enteric commensal bacteria in human colostrum and serum. Forty nine colostrum samples were studied; all of them displayed secretory IgA (sIgA) antibodies reacting with Bacteroides thetaiotaomicron, Clostridium perfringens and Escherichia coli serotype O141:H32 without any K antigen. The amount of sIgA antibodies was always related to the sIgA colostral concentration varying greatly from one patient to another. For the 3 lactating women studied, the colostrum sIgA antibodies were largely predominant as compared to the antibodies of other classes; in their sera, no antibody having the same anticommensal specificity was detected in the IgA fraction while these antibodies were found in IgM and IgG. Our results are incompatible with the existence of local antigenic stimulation, and the IgA transfer from serum into mammary secretion appears unlikely, but these results are perfectly compatible with the antigenic stimulation of gut associated lymphoid tissue and subsequent migration in mammary tissue.

Antibodies, Bacterial↗
PubMedDate not supplied

[Characterization of the antigen in circulating immune complexes and application to the detection of streptococcal antigens in human infectious endocarditis].

Immune complexes from patients with subacute endocarditis were used to develop a methodology for characterization of the antigen involved in human circulating immune complexes. This model was chosen because it permits isolation of the causative agent of the streptococcal infection thought to contain the antigen present in the immune complex. A comparison was made between two methods for characterization of bacterial antigen bound to antibody. In the first, animals were immunized with purified immune complexes and the production of antistreptococcal antibodies was investigated. In the second method, a sandwich ELISA was developed, implying the double specificity of the immune complex (human immunoglobulin and streptococcal antigen). The latter method gave the best results, detecting antigen in the immune complexes of 8 out of 10 patients' sera. The application of this method to other immunopathological situations is discussed.

Animals↗
PubMedDate not supplied

Detection of Legionella pneumophila antigen by ELISA in urine or experimentally infected guinea-pigs.

Guinea-pigs were experimentally infected with Legionella pneumophila. L. pneumophila antigen was detected in urine samples by a double antibody sandwich ELISA. Urinary antigen was present from the beginning of the acute phase of the disease. In two out of five cases, this antigen was found with no antibody detectable in sera by indirect immunofluorescence staining.

Animals↗