Biomedical subjects
Publications and source records attributed to C Rivat.
Genetic polymorphism of the third component of human complement (C3) has been considered as a powerful marker for population genetics. Some studies on the distribution of gene frequencies have been performed among numerous populations all over the world. This review takes stock of population genetic studies reported up to now and points out some remarks on the distribution of the observed allelic frequencies.
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IgA1 populations were reduced over a range of dithiothreitol concentrations and the products were examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and peptide mapping. The study showed that IgA was more resistant to reduction than other immunoglobulin classes (IgG, IgM). SDS-polyacrylamide gel electrophoresis showed that intersubunit bond and H-L bond were the most labile disulfide in polymeric and monomeric IgA, respectively. Peptide mapping revealed that the itrachain disulfide of the C alpha 2 domain was more or equally sensitive to the reduction than H-L and intersubunit bonds. Electrochemical experiments demonstrated that this bond had redox properties and the possibility involving disulfide exchange is discussed.
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Human Properdin factor B and C3 polymorphisms are of a real usefulness as genetic markers for population studies. In addition, they are more and more used for the determination of paternity cases. The present communication will be about Bf and C3 allele frequencies in two locally populations of France, Normandy and Western Pyrenees (Basques), The corresponding allele frequencies are as follows, for Normans : Bf(S) = 0.7422, Bf(F) = 0.2285, Bf(F1) = 0.0205, Bf(SO.7) = 0.0088; CsS = 0.788, C3F = 0.204, C3Srare = 0.004, C3Frare =0.004; and for Basques : BfS = 0.5625, BfF = 0.305, BfF1 = 0.1235, BfSO.7 = 0.0075; C3S = 0.7075 and C3F - 0.2925. French Basques are characterized by unusual allele frequencies in European Caucasoid populations for Bf as for C3 genes. A very high incidence of BfF1 allele is reported (BfF1 = 0.125), as previously observed [7, 17].
Several biological effector functions mediated by sites on the Fc region of human IgG1 have been studied in two variant IgG1 kappa monoclonal proteins (Dob and Lec) which contain deletions corresponding to the entire hinge region of the heavy chains. Neither Dob nor Lec protein in aggregated form was able to activate the classical complement pathway, and this was shown to be due to an inability to bind the first component of complement (C1). By rosette inhibition assays, Dob and Lec proteins were shown to have no measurable affinity for Fc receptors on human B cells or neutrophils. Dob and Lec proteins had a much reduced affinity for Fc receptors on the murine macrophage-like cell line P388D1 when compared to normal human IgG1. Furthermore, the hinge-deleted proteins were able to compete with murine IgG2b for P388D1 receptors but not with murine IgG2a. In contrast, the binding of Dob and Lec proteins to protein A from Staphylococcus aureus was entirely normal. The functional consequences of the hinge deletion were parallel to those seen when normal IgG1 was reduced and alkylated. It was concluded that the functional impotency of Dob and Lec proteins was related to the close association between the Fab and Fc regions in these molecules and the limited degree of segmental flexibility permitted in the absence of the hinge region. The data also suggest a major role for the C gamma 2 domain (C is the constant region) in mediating effector functions in normal IgG1.
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This paper describes a three-step purification method for the third component of human complement (C3) from plasma. The method consists of PEG precipitation, DEAE-cellulose chromatography and preparative isofocusing in a granulated dextran gel, with pH range 5--8. From this last step, a highly purified form of native C3 was obtained as indicated by immunoelectrophoresis and polyacrylamide gel electrophoresis analysis. The average final recovery was 20%.
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Sixty-eight human lambda-chain sources including representatives of the five different subgroups were studied for the distribution of the serologic markers ST, 111, and VOR The variable region character of these antigenic determinants has been demonstrated for those proteins whose primary structures had been partially or completely determined previously. The lambda-chain sub-groups I and IV are readily distinguished antigenically but the specificity designated VOR is shared between them and is absent in the II, III, and V subtypes. The results of these studies are discussed with respect to the possible relationships of the structural genes controlling the synthesis of the lambda-chain subgroups, and some potential phylogenetic and functional meaning of the heterogeneities is revealed.
The cysteinyl peptides of monomeric and polymeric IgA were studied by comparative autoradiography. Autoradiographies of polymeric IgA (containing or lacking J chain) showed an extra cysteinyl peptide which was never found in the monomeric forms. A similar peptide was obtained when reduced IgA was cleaved by BrCN. The possible identity of this fragment is discussed.
27 patients with SSM or NM level IV and V have been submitted to a monthly evaluation of their level of 5-S-cysteinyldopa in the urine and IgG4 subclass in their sera. For 5 patients who entered the stage II of their disease during the follow-up, 3 had elevation of the 5S and 5 had large variations of IgG4. On 21 patients in clinical remission, 10 had conjunctly an increase of 5S and variations of IgG4. The predictional value of these tests is discussed.
A new allotype in the Gm system (Gm(28)) was described and studied. Among Caucasoids and Mongoloids, it was found with rare exceptions, in samples containing Gm(21), segregating with Gm1,17,21 and Gm1,2,17,21 haplotypes. This new antigenic determinant was found to be of particular interest among Negroid populations in which its frequency is variable. It can be detected with all--common or uncommon--haplotypes. The degree to which it is associated with some haplotypes in different populations may prove useful in the characterization of Negroid populations. This new allotypic determinant is located on the CH3 homology region of IgG3 subclass.
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