Anti-idiotypic antiserum to monoclonal anti-Sm inhibits the autoantigen-induced proliferative response.

Anti-idiotypic sera were produced in BALB/c mice against three established monoclonal anti-Sm antibodies. Inhibition assays showed that the anti-idiotypic antibodies recognized determinants that were present on all three monoclonal antibodies but not on normal mouse IgG from unimmunized BALB/c mice or myeloma proteins. Normal (+/+) and autoimmune (lpr/lpr) MRL/MpJ or C3H/HeJ mice were immunized with Sm in complete Freund's adjuvant. Immune T cells from the draining lymph nodes proliferated in response to the addition of Sm in vitro. Anti-idiotypic serum added to these cultures inhibited the proliferative response by 50 to 70%, whereas normal BALB/c serum had no effect. This inhibition of proliferation was antigen specific, because the anti-idiotypic serum did not inhibit the T cell proliferative response to an irrelevant antigen, TNP-KLH, or ovalbumin. Kinetic studies showed that the anti-idiotypic serum inhibited an early event in antigen-induced proliferative response, because the addition of serum late in culture did not cause any significant reduction in proliferation. The reduced proliferative response was due to direct action of the anti-idiotypic serum on the Lyt-1+, 2- T cell population.