In vitro inhibition of the classical and alternate pathways of activation of human complement by N acetyl aspartyl glutamic acid (NAAGA).

A synthetic dipeptide, magnesium salt of N-acetyl-L-aspartyl-glutamic acid (NAAGA) identical to a natural dipeptide found as traces in cerebral tissues of mammalian brains, was shown to inhibit, in vitro, the hemolytic activity of both classical and alternate pathways complement; the required concentration of NAAGA was 2 to 10 mM. Cross immuno electrophoretic analysis demonstrated an inhibition of C3 cleavage by both classical and alternate pathway C3 convertases with 24 mM NAAGA. As expected, if C3 convertases were really the target of inhibition, the release of highly inflammatory C3a, C5a fragments scored by R.I.A. was impaired when complement was incubated with activators of classical and alternate pathways. Such a low molecular weight dipeptide, quite atoxic and inhibiting the complement dependent cytotoxicity and release of phlogistic by-products could be interesting for pharmacological manipulation of complement activation in inflammatory processes.

Immuno-enzymatic study of IgG subclasses specific for allergen in house dust immediate hypersensitivity.

Investigation of the serum-specific IgE by the RAST technique and of the four specific subclasses of IgG in house dust allergy by an immuno-enzymatic assay was made among healthy control subjects, non-treated atopic patients and hyposensitized patients. There was evidence that the titer of specific IgE remains high in the treated patients regardless of their improvement or non-improvement clinically. A good prognostic significance, however, correlates with a low specific IgG4 titer in the serum, but the pathogenic significance of IgG4 cannot be determined until these immunoglobulins can be studied on the membrances of circulating basophils of hyposensitized patients.

[Study of X antigen of Salmonella typhi responsible for the production of protective antibody towards chick embryo]. / Recherche sur l'antigène X responsable de la production des anticorps anti-Salmonella typhi, protecteurs pour l'embryon de poulet

Laboratory animals are not sensitive to human S. typhi strain (O+ Vi+). But the chick embryo is very susceptible to infection by this strain. This property can be used to test protective activity of immuno sera. Several antigenic fractions have been prepared from Ty6S strain (0- Vi+) by washing methods. The " outer layer " of the bacteria is easily removed by NaCl 0,5 M. Injected in rabbits this preparation produces the synthesis of protective antibodies. The active antigen X is spun down with the Vi antigen. The relation of X antigen to Vi antigen is being studied.

[Do immunization of rabbits by N-acetylgalactosamine and a disaccharide linked to a protein produce anti-microbial antibodies (author's transl)]. / Essai de production chez le lapin d'anticorps antimicrobiens par immunisation avec la N-acétylgalactosamine et un dioside liés a une protéine

Rabbits were immunized with N-acetylgalactosamine linked to bovalbumine. They produced antibodies which precipitated this same sugar linked to human gamma-globulins but did not agglutinate Salmonella johannesburg which carry a side chain of N-acetylgalactosamine. The same immunization enhanced the titre of "natural" antibodies agglutinating human A red cells (which carry a terminal N-acetylgalactosamine) but they did not evoke such antibodies in rabbits with no "natural" hemagglutinins. These negative results, when compared to the positive one obtained with 0-acetyl-3,6-dideoxygalactose suggest that rabbit antibody-sites limited to one sugar may exist but that they can be detected only under certain conditions. Another group of 8 rabbits was immunized with a disaccharide alpha-Glc-(1 leads to 6)-GalNAc linked to a protein. All produced antibodies agglutinating S. johannesburg (1,40) which carry this disaccharide and S. senftenberg which carry the disaccharide alpha-Glc-(1 leads to 6)-Gal. The titres of these antibodies decreased after a second course of immunization.