Detection of autoantibodies to Sm antigen in systemic lupus erythematosus by immunodiffusion, ELISA and immunoblotting: variability of incidence related to assays and ethnic origin of patients.

Autoantibodies to small nuclear ribonucleoproteins (snRNP) were studied using the techniques of immunodiffusion, ELISA, and immunoblotting in the sera of 150 patients with systemic lupus erythematosus (SLE), and of 29 patients with mixed connective tissue disease; 900 control patients and 100 normal blood donors were examined simultaneously. The incidence of anti-Sm antibodies in French SLE patients was low compared with the occurrence observed in similar studies in USA (even when highly sensitive assays were used) but was of the same magnitude as European results. Frequency of anti-Sm antibodies in SLE patients varied moderately when detected by immunodiffusion (12%), or by immunoblotting (17%), however, it seems that the ethnic and/or genetic background of patients induces more significant differences. SLE patients from the French West Indies had anti-Sm antibodies in 39% of cases when detected by immunodiffusion and in 50% when immunoblotting was used. In these patients the incidence of the antibodies was five times more frequent than that of mainland French patients. Immunization against snRNP does not seem to be a common feature of all SLE patients.

Study on plant RNAases. Isolation and properties of several activities from Vicia faba root cells.

Vicia faba root cells contain several nucleolytic activities: phosphomonoesterase and phosphodiesterase (which however were not studied in details), one nuclease and four ribonucleases. These results were obtained by separating the extracted proteins into anionic and cationic species by chromatography on CM-cellulose at pH 5.5 and analysing each kind of proteins. Anionic species were subjected to chromatography on DEAE-cellulose which lead to isolation of one nuclease (A1) and two RNAases (A2, A3), the properties of which were studied. It was shown that the RNAases pH optima are near 6; A2 is more thermolabile than A3; both are endonucleases unable to attack double-stranded structure; studies with homopolymers, i.e. poly(A), poly(I), poly(C), poly(U), showed that their base specificities were analogous to that of already known plant RNAases. The cationic proteins, analysed with CM-cellulose, contain two RNAases (C1, C2). The pH optima were near 6 and 7, respectively; C1 is much more thermolabile than C2; both were endonucleases inactive on double-stranded structures. C1 and C2 hydrolysed poly(C) and poly(U) but not poly(A) and poly(U).