Shifts of anti-Sm-specific antibodies in patients with systemic lupus erythematosus: analysis by counter-immunoelectrophoresis, immunoblotting and RNA-immunoprecipitation.

We investigated serial changes in anti-Sm-specific antibodies by counter-immunoelectrophoresis (CIE), immunoblotting (IB) and RNA-immunoprecipitation (RNA-IP) in three patients with SLE. To assess the immuno-regulatory processes underlying anti-Sm antibody production, we compared changes in anti-Sm-specific antibodies with changes in titres of antinuclear and anti-ds DNA antibodies. IB and RNA-IP detected anti-Sm antibodies earlier than did CIE. The induction of the immune responses against the Sm-specific BB' and D polypeptides occurred separately in two of the three patients. Anti-Sm developed in all three cases after a flare-up of disease, whereas anti-ds DNA antibody levels fluctuated in parallel with disease activity. Thus, anti-Sm and anti-ds DNA antibody production seems to be independently regulated.