[Sensitized immunofixation: a new technique for analyzing the oligoclonal pattern of CSF immunoglobulins]. / L'immunofixation sensibilisée: nouvelle technique d'analyse du profil oligoclonal des immunoglobulines du LCR.

Intrathecal immunoglobulin synthesis is observed in more than 90% of all cases of multiple sclerosis, producing a specific CSF IgG oligoclonal electrophoretic pattern. The consensual method used as reference is isoelectric focusing (IEF). We developed a new CSF Ig analysis method by immunofixation (IF). The method includes an immunoenzymatic detection step performed directly on the gel allowing the use of unconcentrated CSF and avoiding the blotting step. The reliability of this method was established by the analysis of 210 CSF/serum pairs including defined, probable and possible MS, other inflammatory CNS diseases and controls (noninflammatory CNS diseases and peripheral nervous system diseases). Intrathecal IgG synthesis was detected in 95.5% of defined MS cases. The specificity for CNS inflammatory diseases including MS diagnosis, evaluated by comparison with controls, was 98.8%. This new method is quicker and visual interpretation is easier than with IEF. It is a semi-automated method that should be considered for standardization of CSF IgG analysis.

[Antigenic structure of a fragment of human serum albumin]. / Etude de la structure antigénique d'un fragment de sérum albumine humaine

The antigenic structure of a fragment (F1) of human serum albumin (HSA), carrying one of the antigenic sites of the whole molecule, has been studied. Previous studies have shown that this fragment is made of two peptide chains linked by a disulfide bond. One of these chains named alpha has 28 residues and one intrachain disulfide bond giving rise to a loop of 9 or 10 residues. The chain occurs under two forms: the beta chain made of 25 residues and the gamma chain which differs from the beta chain by the absence of the two last C-terminal residues (F. Bellon and C. Lapresle, Biochem. J., 1975, 147, 585-592). The alpha and beta chains both inhibit independantly at 100% the agglutination by an anti-albumin serum of red cells sensitized with F1. Chains alpha, beta and gamma displace anti-HSA antibodies fixed upon an immunoadsorbent prepared with F1. Chain alpha is more active than chain beta which in turn is more active than chain gamma. Reduction and alkylation of alpha and beta chains abolish almost completely their immunological activity. Immunoadsorbents prepared with alpha or beta chains adsorb all of the anti-F1 antibodies from an anti-HSA serum. Antibodies isolated from each chain are inhibited by both chains. Chains alpha and beta induce in rabbits the formation of antibodies reacting with F1 and HSA, alpha chain being a better immunogen than beta chain.

Chemical structure of two fragments of human serum albumin and their location in the albumin molecule.

1. 'Inhibitor fragment' isolated from human serum albumin degraded by rabbit cathepsin D is composed of one peptide chain with two intrachain disulphide bonds. There are two kinds of inhibitor molecules having different N-terminal amino acids: one is threonine and the other glutamine. 2. Fragment F1, isolated from inhibitor degraded by trypsin, is composed of two chains linked by a disulphide bond. There are three kinds of fragment F1. All have one alpha chain in common, which has an intrachain disulphide bond. They differ by the nature of the chain, which is linked to the alpha chain by a disulphide bond. The epsilon chain is present in trace amounts. The two other chains, beta and gamma, differ by their C-terminal amino acid, which is respectively arginine and lysine. 3. Inhibitor is composed of the last 92 or 89 residues of the human albumin molecule and fragment F1 is composed of two parts of this C-terminal portion of the albumin molecule.