Private idiotypes on human polyclonal IgG anti-DNA antibodies are not expressed on coexisting IgM anti-DNA antibodies in systemic lupus erythematosus

Shift of private and not of cross-reactive anti-DNA idiotypes in systemic lupus erythematosus

The shift of private idiotype (Id) and cross-reactive Id (CRI) on anti-DNA antibodies in a lupus patient KE was investigated during a 7-year period. Anti-private Id and anti-CRI activities were separated by affinity chromatography from rabbit (R)-anti-Ids raised against KE anti-DNA antibodies during active (1/84) and inactive (4/90) stages of the disease. Anti-CRI isolated from the 84 R-anti-Id appeared to recognize binding site-related Ids that are shared with KE non-anti-DNA antibodies, unrelated lupus patients' sera, and certain normal sera. Id expression on serial serum samples of KE using these fractionated R-anti-Ids as probes showed that the 1/84 private Id expression declined while the 4/90 private Id expression gradually increased. Expression of the CRI showed a relatively stable pattern. These results suggest that anti-DNA populations detected by anti-private Id can shift, while populations expressing CRI may stay stable.

Rabbits produce SLE-like anti-RNA polymerase I and anti-DNA autoantibodies in responses to immunization with either human or murine SLE anti-DNA antibodies

Anti-DNA and anti-DNA polymerase I (RPI) autoantibody responses are symptoms of systemic lupus erythematosus (SLE). To investigate the relationship between these antibodies (Ab), rabbits were immunized with one of the following preparations: human SLE anti-DNA Ab; human SLE anti-DNA IgG; normal human anti-DNA Ab; human Grave's disease anti-DNA Ab; murine SLE anti-DNA Ab or anti-DNA IgG Fab; various normal human, murine, or rabbit IgG preparations; or complete Freund's adjuvant (CFA), alone. All of the animals immunized with anti-DNA Ab (n = 14) generated Ab reactive in radioimmunoassay with: ssDNA, dsDNA, RPI, the soluble fraction of rabbit liver crude nuclear extract, and the immunogen. Induced rabbit anti-DNA Ab in turn induced these responses in a different rabbit: a rabbit immunized with rabbit anti-DNA IgG Ab which had been previously induced by immunization with human anti-DNA Ab, produced Ab reactive with ssDNA, dsDNA, RPI, and the soluble fraction of rabbit liver nuclear extract. Although an individual animal's antisera reacted consistently over the course of immunization with the same individual RPI subunit(s), antisera from different animals reacted with different subunits of the 9-subunit RPI complex in Western blot analyses: 190 kD (n = 6); 120 kD (n = 1); 62 kD (n = 4); 45 kD (n = 2); and, no reactivity (n = 2). In contrast, animals immunized with normal IgG or CFA produced responses only against the immunogen. Together, these data suggest that anti-DNA and anti-RPI responses are connected through an autoimmune network in SLE.

Idiotypic and immunochemical differences of anti-DNA antibodies of a lupus patient during active and inactive disease

IgG anti-DNA antibodies of a lupus patient during active and inactive stages of her disease were studied. There were no significant differences in the amounts, in double-stranded DNA-binding activity, or in complement-fixing ability between purified IgG anti-DNA antibodies of both stages. However, their idiotype (Id) expressions were different as revealed by binding to rabbit anti-Ids raised against each of the anti-DNA antibodies. Moreover, the active stage anti-DNA antibodies had higher activity and less cross-reactivity with polynucleotides. Dominant anti-DNA populations during the active and inactive stages of systemic lupus erythematosus are clonally and qualitatively different.