A multiple sample immunoblotting system (MSIS) for the intrinsic detection of antinuclear autoantibodies

Hep-2 cell based indirect immunofluorescence assay for antinuclear antibodies as a potential diagnosis of drug-induced autoimmunity in nonclinical toxicity testing

Antinuclear antibodies (ANAs) are important biomarkers in the diagnosis of autoimmune diseases in humans; however, the diagnostic performance of ANA in nonclinical safety studies are not well understood. Here, we studied the use of ANAs as potential nonclinical biomarkers for drug-induced autoimmunity (DIA) using a Hep-2 based indirect immunofluorescence assay (IFA). Initially, MRL-fas(lpr)/J mice and HgCl₂-treated rats were used as SLE-positive models. Serum samples obtained from 94 normal mice or 204 normal rats aged one to four months served as the negative control. The IFA effectively distinguished ANAs-positive samples in both species with a cut-off titer of 1:100. Brown Norway rats were treated with 450 mg/kg D-penicillamine for 30 consecutive days. ANAs were generated and corresponded with DIA development. Human Hep-2 cells, mice Neuro 2A cells, and Chinese Hamster Lung cells served as antigen from different species, which were found cross-reactive with ANA-positive serum samples from mice, rats, and humans without any differences in diagnosis. This methodology showed no species-specificity for ANA detection. Furthermore, we found approximately 20 percentage of the mice aged seven to eight months demonstrated age-related ANAs, which was consistent with humans. Overall, our findings demonstrated the use of ANA detection using IFA in the nonclinical diagnosis of murine drug-induced autoimmunity, and age-related ANAs should be considered when aged animals are used.

Anti-Sm sera are misdetected by counterimmunoelectrophoresis. A critical analysis of CIE and western blotting on the detection of human antinuclear antibodies

The ability of CIE and Western blotting to detect antibodies against the Sm, RNP and SS/B antigens was tested in 84 sera from SLE patients. CIE and Western blotting gave identical results for anti-RNP and anti-SS/B; positivity was detected in the same sera regardless of the technique used and no new positive sera were found by Western blotting among those classified by CIE as not showing immunological relationship to the anti-RNP and anti-SS/B references. CIE detected only half of the anti-Sm that were positive by Western blotting. The inability of CIE to detect sera positive for anti-Sm could not be ascribed to specific features of the sera, such as low titer or the lack of antibodies to the Sm antigens B/B' and/or D. The identity of a number of these new anti-Sm sera was confirmed by the utilization of an in vitro translation test, where the 'cell-free' translation products were immunoprecipitated with the new positive anti-Sm sera.

SS-B (La) nuclear antigen: fast and non-degradative procedure to prepare SS-B extracts free from other nuclear antigens

A procedure is described allowing the easy and fast obtention of a cellular extract from calf thymus, enriched in the undegraded 52 kDa SS-B protein. As seen by western blot, the extract does not contain Sm and RNP antigens, allowing the use of such fraction for the detection of anti-SS-B antibodies without the interference of the anti-Sm and anti-RNP specificities. The enrichment avoids denaturing agents, making the fraction suitable for use in functional and structural studies.

SS-B (La) nuclear antigen. Organization in structural domains of the protein moiety

Stable degradation products, obtained by digestion with endogenous and V8 proteases of calf thymus SS-B (La) antigenic protein, have been studied. The most characteristic fragments have molecular masses of 47, 30, 23 and 17 kDa. The 47-kDa and 30-kDa fragments are complex and are constituted of a number of species of different isoelectric points, as has been described for the SS-B protein molecule from other sources. Degradation products from the entire SS-B nuclear antigen still contain the 30-kDa SS-B fragment, suggesting that the 30-kDa region of the SS-B protein molecule is firmly attached to the RNA moiety. A model is presented that implies the presence of two hinge regions sensitive to proteases and three structural domains that correspond to segments of 30 kDa, 17 kDa and 5-6 kDa.