Presence of auto-anti-idiotypic antibody during the normal human immune response to tetanus toxoid antigen.

Auto-anti-idiotypic antibodies were searched for in the serum of two individuals who received booster immunization with tetanus toxoid (TT) antigen. IgG from serial bleeds obtained for 4 mo after immunization was studied a) for its capacity to specifically bind 125I IgG F(ab')2 anti-TT prepared from serum obtained 7 and 10 days post-booster immunization, and b) for its capacity (after its absorption with TT) to specifically inhibit the binding of 125I-radiolabeled TT to IgG obtained 7 and 10 days post-immunization and designated "peak IgG." In both individuals studied, auto-anti-Id IgG were detected in both assays as early as 2 wk post-booster immunization and remained detectable throughout the study period. Evidence for modulation of idiotypic expression on IgG F(ab')2 anti-TT after booster immunization with TT was obtained by studying a) the capacity of serial IgG samples to inhibit the binding of 125I-IgG F(ab')2 anti-TT to rabbit anti-Id antibody raised against the IgG F(ab')2 anti-TT, and b) the capacity of the rabbit anti-Id to specifically inhibit the binding of 125I-TT to serial samples of serum IgG. Both assays indicated that some idiotypic determinants present on anti-TT obtained before and shortly after booster immunization were expressed to a much lesser extent 2 wk and beyond after immunization. The decrease in the expression of these determinants coincided with the appearance of auto-anti-Id antibody and remained evident throughout the 4-mo study period. The results obtained indicate that auto-anti-Id antibodies arise in normal human subjects after a secondary challenge with antigen and suggest that these antibodies may play a role in the modulation of idiotypic expression that is observed after booster immunization with antigen.