Binding of IgG to detergent-extractable constituent(s) of silicone elastomer

The potential for specific interactions between the human immune system and silicones remains highly controversial. We have previously reported enhanced binding to silicone elastomer of IgG from the sera of the rare children who develop local reaction to their silicone shunts. Progress in understanding the basis for this increased binding has been impeded by the imprecision in the binding assays. We recently found that the major moieties of the silicone elastomers, to which IgG binds could be extracted in non-ionic detergent and used to sensitize polystyrene plates for IgG binding assays. The serum IgG binding to silicone extract-coated plates and silicone elastomer fragments were highly correlated. The extract-treated plate assay was used to reexamine the basis for enhanced IgG binding from the sera of three shunt patients, when compared to three control sera. We confirmed that the binding to silicone of purified IgG from each of the sera was greater than the IgG binding from an equivalent amount of whole serum. However, this difference was much less pronounced for the patients' samples. Mixing experiment indicated that the enhanced IgG binding from whole patient serum (compared to normal sera) was a property of their IgG, rather than a difference in capacity of the sera to modulate IgG binding. Sequential incubation of silicone-treated wells with serum depleted of IgG, followed by purified IgG suggested that the effect of serum on IgG binding was due to competition for silicone binding sites. Thus, the IgG from patients' sera seem to compete more effectively with other serum factors for binding to the extractable component of silicone elastomers. The affinity and specificity of the IgG which binds to silicones may best be tested on pure constituents of the extractable fraction of silicone elastomer.