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Biomedical subjects

G Lefranc

Publications and source records attributed to G Lefranc.

At least 109 records · Page 6Linked to original sources
PubMed1988

Further contribution of common Gm*-Am* haplotypes and Km* alleles in the characterization of the Tunisian population.

The Gm, Am and Km allotypes have been investigated in 405 sera from unrelated students and blood donors coming from the different areas of Tunisia. Thirty Gm and fourty-seven Gm-A2m common phenotypes have been observed. Eleven Gm* and seventeen Gm*-A2m* common haplotypes have been deduced from these phenotypes. The Tunisian population appears as mainly Caucasoid (combined frequency of Caucasoid Gm*-Am* haplotypes in the order of 0.81-0.82) with a relatively important Black contribution in the gene pool (combined frequency of Negroid Gm*-Am* haplotypes of 0.17-0.18) and a very low Oriental participation (0.01-0.02). Our results are compared to those previously reported for two other samples of the Tunisian population, the first from the regions of Mahdia and Sfax and the second from several villages of Berbers, the first inhabitants of Tunisia. Likewise, other comparisons are made with populations from Africa, Europe and Asia, since Tunisians are a mixture of Berbers, invaders and immigrants from different origins.

Female↗
PubMed1988

Uncommon Gm* haplotypes in the Tunisian population: further contribution to the genetics of the IgG immunoglobulins.

In this work, eight family studies were conducted to establish the suspected unusual Gm* haplotypes in 13 persons (among 418) showing uncommon Gm phenotypes. Usually, the Gm (21 and 28)--or Gm (g1 and g5)--allotypes are both present or absent. Exceptions to this rule were observed: on the one hand, only the Gm (28) allotype was present in 12 persons, and on the other hand, only the Gm (21) allotype was found in 1 person. Such events could be explained, in some cases, by equal crossovers or point mutations, and, more generally and very likely, by gene conversions. Other interesting results are also presented, as, on the one hand, silent genes homozygous at the C gamma 4 locus and, on the other hand, a homozygous multigene deletion encompassing the C alpha 1, psi gamma, C gamma 2 and C gamma 4 loci.

Chromatography, Affinity↗
PubMed1987

Human immunoglobulin heavy-chain multigene deletions in healthy individuals.

Extensive multigene deletions have been described in the human immunoglobulin heavy-chain constant region genes, some of them encompassing perhaps more than 100 kilobases. These deletions have all been observed in healthy individuals although these individuals lacked several immunoglobulin class or subclasses, being either homozygous for one deletion or heterozygous for two different deletions. The high frequency of consanguinity in the Tunisian population accounts for the high frequency of individuals displaying one or the other of these deletions in a homozygous state.

Chromosome Deletion↗
PubMed1987

Subclass restriction pattern of antigen-specific antibodies in donors with defective expression of IgG or IgA subclass heavy chain constant region genes.

We have developed a method for the measurement of the IgG and IgA subclass distribution of antigen-specific human antibodies. The controls for the specificity of the assay include the use of a number of monoclonal human antibodies and sera from individuals with deletions of particular immunoglobulin heavy chain constant region genes. The system was used to determine the shift in immunoglobulin subclass patterns of specific antibodies against a variety of protein and polysaccharide antigens in individuals with a regulatory deficiency of a given IgG or IgA subclass. Normally, the pattern is quite distinct and antibodies against protein antigens are mainly of the IgG1 subclass, whereas antibodies against polysaccharide antigens are mainly of the IgG2 subclass. The results on serum from an IgG1 deficient donor suggested that IgG3 and IgG4 appear to compensate for a lack of IgG1, whereas isolated deficiencies of IgG3, IgG4, or IgA2 do not markedly influence the expected distribution of specific antibodies. In IgG2-deficient individuals a more complex pattern was observed where antibodies against protein antigens were retained, whereas levels of antibodies against polysaccharide antigens could vary markedly between donors, which appeared to be dependent on whether the IgG2 deficiency was an isolated defect or combined with IgG4/IgA deficiency. However, all the IgG2-deficient donors had a skewed pattern of anti-polysaccharide antibodies with a shift to IgG1 to IgG3.

Antibodies↗
PubMed1987

Human immunoglobulin C lambda 6 gene encodes the Kern+Oz-lambda chain and C lambda 4 and C lambda 5 are pseudogenes.

Six nonallelic immunoglobulin lambda constant region genes have been previously characterized on a 40-kilobase stretch of DNA. The nucleotide sequences of the three upstream genes of this cluster (C lambda 1, C lambda 2, C lambda 3) have been determined by other workers and shown to encode, respectively, the isotypic Mcg, Kern-Oz-, and Kern-Oz+ constant region of the lambda chains. In this paper, we report the sequence of the three downstream genes of this cluster and show that two of them (C lambda 4 and C lambda 5) are pseudogenes. However, C lambda 6 encodes a Kern+Oz- chain and corresponds to the fourth isotype described among the lambda proteins sequenced so far. A potentially active J lambda (joining) segment, with the canonical heptamer and nonamer sequences for rearrangement, is located 1.5 kilobases upstream of C lambda 6. The amino acid sequence encoded by the C lambda 6 gene is compared with the constant region sequences of various monoclonal Bence Jones lambda proteins. Allotypic and isotypic differences confirm the polymorphism and complexity of the human C lambda locus.

Amino Acid Sequence↗
PubMed1987

Generation of the antibody repertoire in individuals with multiple immunoglobulin heavy chain constant region gene deletions.

Antibodies against protein antigens are largely restricted to the IgG1 subclass in man, whereas anti-carbohydrate antibodies, at least in adults, are almost exclusively confined to the IgG2 subclass. In IgG2-deficient donors where the C gamma 2 gene is retained in the genome, antibodies against most polysaccharide antigens are absent. We therefore undertook a study of the antibody repertoire in 11 adult donors with immunoglobulin heavy chain constant region gene deletions, homozygous or heterozygous defects, encompassing the C gamma 2 gene. In all cases, antibodies against polysaccharide antigens were present and restricted to the remaining subclasses (IgG1 and/or IgG3). These results suggest an unrestricted use of the available VH gene repertoire in donors lacking the C gamma 2 gene, and imply that the limited antibody repertoire found in IgG2-deficient individuals with a retained C gamma 2 gene may be a consequence of an altered regulatory mechanism or a structural VH gene defect. However, furthermore, the deletion of multiple C gamma heavy chain constant region genes did not appear to decrease the IgG switch probability as such, since total serum levels of IgG appear to be normal.

Antibody Formation↗
PubMed1987

Polymorphism of the complement C3 gene in the Lebanese population.

The C3 protein polymorphism was studied in 300 unrelated Lebanese. The gene frequencies were calculated and compared with other populations. DNA samples digested with various endonucleases were hybridized with a C3 probe, which was found to detect a frequent Sac I restriction fragment length polymorphism (RFLP) and a less frequent Taq I RFLP in the Lebanese population, as well as in the French populations.

Alleles↗
PubMed1986

A gamma 3 hinge region probe: first specific human immunoglobulin subclass probe.

We report the first specific human immunoglobulin subclass probe which was obtained by subcloning the gamma 3 hinge region. This specific gamma 3 probe allowed us to identify with certainty the C gamma 3 gene on Southern genomic blots, to describe the first C gamma 3 restriction fragment length polymorphism (EZZ gamma 3 RF) and to show that an IgG3 selective deficiency, previously described serologically, was not due to a deletion of the C gamma 3 gene. Such a probe should be particularly useful for screening libraries from individuals with IgG3 immunodeficiencies or presenting unusual C gamma 3 genes and, consequently, for studying the C gamma gene evolution.

Amino Acid Sequence↗
PubMed1986

Sequence of a human immunoglobulin gamma 3 heavy chain constant region gene: comparison with the other human C gamma genes.

We report the first and complete nucleotide sequence of a human gamma 3 heavy chain constant region gene (C gamma 3). This gene displays the same organization than the others C gamma genes and exhibits normal RNA splice and polyadenylation sites. A comparison of its primary sequence with those of C gamma 1, C gamma 2 and C gamma 4 genes confirms the high degree of homology (95%) of the human family in both coding and non-coding regions, and the divergence of the hinge region. The C gamma 3 gene we sequenced codes for a Gm(b) gamma 3 chain (EZZ). Comparison with other known protein sequences reveals that only two specific aminoacids are involved in the Gm(b) and Gm(g) allotypes, which suggests an important part of the spatial configuration in the allotypic specificities.

Amino Acid Sequence↗
PubMed1986

Gene conversion in human immunoglobulin gamma locus shown by unusual location of IgG allotypes.

The constant region of the gamma 1, gamma 2 and gamma 3 heavy chains of the human IgG1, IgG2 and IgG3 immunoglobulins carries antigenic determinants or G1m, G2m and G3m allotypes, which are genetic markers of these subclasses. The exceptional presence on gamma 1 and gamma 2 chains of Gm allotypes usually located on the CH3 domain of gamma 3 shows an unexpected clustering of base changes and subsequent identity of short DNA sequences in the CH3 exon of the non-allelic gamma 1, gamma 2 and gamma 3 genes. Such clusters of substitutions are not easily explained on the classical basis of point mutations. A gene conversion, which substituted a segment of the gamma 1 or gamma 2 gene with the homologous region of the non-allelic gamma 3 gene, is more likely. Other examples of possible conversion involving the gamma genes are described. The conservation or the restoration of short sequences produced by the conversion events might be related to the biological properties of the constant region of the heavy chains.

Alleles↗
PubMed1984

Inulin-induced activation of factor B in whole serum: description of structural modifications in the Ba fragment.

The investigation of inulin-induced conversion of human factor B in serum by isoelectrofocusing revealed physiological modifications in the primary structure of the Ba fragment. Evidence has been obtained that a nascent Ba, generated by the hydrolytic action of the D component on B in serum, was a short-lived product and that a fast release of carboxy-terminal arginine and lysine residues occurred involving a serum carboxypeptidase B enzyme.

3-Mercaptopropionic Acid↗
PubMed1984

Genetic study of Tunisian Berbers. I. Gm, Am and Km immunoglobulin allotypes and ABO blood groups.

The Gm, Am and Km immunoglobulin allotypes and ABO blood groups were studied in three groups of Tunisian Berbers . The results showed that the actual Berbers of Tunisia present certain heterogeneity and their ancestors were probably the first inhabitants of North Africa. Indeed, although their Gm-Am haplotypes are mainly Caucasoid, some of them are typically African. The group of Kesra village, the most Caucasoid, shows frequencies of Gm-Am haplotypes very close to those of South European populations, particularly the Spanish, who are probably of the same origin. The gene frequencies of the ABO groups in the three Berber groups were similar to those recorded in European populations with a relatively high frequency of the O genes typical of the Berbers .

ABO Blood-Group System↗
PubMed1984

Quantitative assessment of the glandular activity of endocrine cells of gastrointestinal mucosae by computer-assisted analysis of ultrastructural images: methodology.

A method is described for studying the morphological features of endocrine cells of gastrointestinal mucosae in man and some animal species by semi-automatic analysis of ultrastructural images. The method enables possible ultrastructural variations in gastrointestinal endocrine glandular cells of different types to be determined with an acceptable margin of error. Various causes of error are investigated. It is found that the main cause is the choice of microscope magnification, despite the corrections made. The factor of inconsistency in the reproducibility of measurements performed by several operators is also calculated.

Animals↗
PubMed1984

Genetic study of Tunisian Berbers. II. Alpha 1-antitrypsin (Pi) polymorphism: report of a new allele (Pi S Berber).

The alpha 1-antitrypsin (alpha 1-AT) (Pi) polymorphism has been studied in three Berber groups of Tunisia by high-resolution isoelectric focusing. The results showed that actual Tunisian Berbers are mainly Caucasoid. A new variant of alpha 1-AT, tentatively called Pi S Berber, was found in the three Berber groups. On isoelectric focusing this variant was slightly more cathodal than the product of the usual Pi S allele. Family studies showed that the Gm-Pi linkage is probably close when the Pi locus supports the Pi P allele which is responsible for moderate (30%) serum alpha 1-AT deficiency.

Alleles↗
PubMed1983

Simultaneous absence of the human IgG1, IgG2, IgG4 and IgA1 subclasses: immunological and immunogenetical considerations.

Simultaneous absence of the IgG1, IgG2, IgG4 and IgA1 immunoglobulins has been unambiguously demonstrated in a healthy 75-year-old woman by testing for allotypes, isoallotypes and for isotypes of these four subclasses. Only IgM, IgD, IgG3, IgA2 and IgE were present. The IgG3 levels were significantly increased. Family investigation showed inheritance of a haplotype Gm-;-;b A2m2. This person is homozygous for an extensive DNA deletion including the C gamma 1, C gamma 2, C gamma 4 and C alpha 1 genes.

Aged↗
PubMed1983

HLA A*, B*-BF* and C4 A*, B* allele associations, with special reference to BF*S07, in the Tunisian population.

The HLA A*2, Bw*50-BF*S07-C4 A*2, B*1 linkage group was transmitted unambiguously in four unrelated Tunisian families. In one of these, another allele association, also carrying BF*S07, HLA A*9, Bw*50-BF*S07-C4 A*1, B*1, was encountered. The previously reported linkage disequilibrium between BF*S07 and HLA Bw*50, a subtypic specificity of HLA Bw*21, is confirmed in our study. The C4 A*2, B*1 haplotype, rare in the other populations until now studied, seems more frequent in Tunisia since it has been also found linked to HLA A*11, B*27 and BF*S in one of these families. Other allele associations were unambiguously demonstrated with predominantly the C4 A*3, B*1 haplotype, particularly a rare HLA A*3, B*18-BF*F1-C4 A*3, B*1 linkage group. A silent gene at the C4 A locus was found linked to HLA B*8.

Alleles↗