[Quantitative evaluation of serum IgG subclass levels by an immunoenzyme method]. / Estimation quantitative du taux des sous-classes d'IgG sériques par une méthode immunoenzymatique.

We developed a enzyme linked immunosorbent assay (ELISA) for measuring IgG subclasses concentration in serum. For this we used monoclonal antibodies. The specificity of these antibodies was evaluated with a panel of myeloma proteins belonging to the 4 IgG subclasses. The ELISA was sensitive (allowing the detection of subclasses at ng level) and accurate (inter-assay coefficient of variation of 14%). Using the WHO serum 67/97 as reference, we determined the concentration of IgG subclasses in a pool of sera. In addition concentrations were measured in 69 healthy adults to study the distribution of each IgG subclass. A good correlation (r = 0.78) was obtained between the sum of the subclasses measured by ELISA and total IgG measured by immunonephelometry.

Idiotypic specificity of a human monoclonal anti-Rhesus(D) antibody.

A human monoclonal IgG anti-Rhesus(D) (H2D5D2) obtained after transformation of lymphoid cells by Epstein-Barr virus was purified from culture supernatant by affinity chromatography. Rabbits were immunized with the monoclonal anti-D. The rabbit antisera, after appropriate absorption, reacted only against the immunizing monoclonal anti-D. The antiidiotypic antibodies (anti-id ab) were purified and gave a complete inhibition of the monoclonal anti-D, whereas no inhibition was observed with monoclonal or polyclonal IgG or with sera containing high titres of anti-D. Polyclonal anti-D obtained from 118 immunized blood donors were coated on Rh-positive red cells. Agglutination by anti-id ab was observed in 4 cases (3.4%), indicating a cross-reactivity between the monoclonal anti-D and the polyclonal anti-D present in the sera of some immunized donors.

[High molecular-weight polymers in human albumin solutions. Quantitative determination by polyacrylamide gradient electrophoresis]. / Les hauts polymères dans les solutions d'albumine humaine. Leur évaluation quantitative par électrophorèse en gradient de polyacrylamide.

Isolated albumin almost always contains polymerized forms which appear during preparation and storage of the protein. The proportion of polymerized forms reflects the degree of stability of the solution. The quantitative estimation of the polymers is usually performed by gel chromatography. In this work, the high resolution power of polyacrylamide gradient gel electrophoresis (Gradient PAGE) was used to separate the polymers present in the preparations of human serum albumin. The analysis of the different peaks obtained by gel chromatography allows to conclude that peak 1 contains aggregates and high polymers, peak 2 trimer and dimer and peak 3 the monomer of albumin. The aggregates of the peak 1 can be dissociated by SDS and correspond, in gradient PAGE, to the high polymers. By using gradient PAGE in the presence of SDS under the conditions described in this paper, it is possible to estimate the proportion of high polymers and aggregates present in albumin preparations. These results are similar to those obtained by chromatography followed by a protein assay but noticeably inferior to those resulting from measurements performed by absorbance at 280 nm.