implant in the body. At the end of the experiment, the rats were sacrificed, their serum tested for antibody to BSA, and the injection sites examined histologically for evidence of inflammation.

A third experiment was performed to determine if the antigen (BSA) must be carefully and extensively homogenized with the gel/oil combination before injection or whether the two ingredients could simply be mixed as would occur in the body.

Findings

The gel/oil combination was compared with Freund's adjuvant in its ability to potentiate the response to a foreign substance (BSA); the two adjuvants proved to be equivalent. These results confirmed the findings of the Rochester group and extended them to another species, the mouse. In contrast to the results of the first experiment, neither the large nor the small particles of the silicone elastomer had any adjuvant effect when mixed with BSA. The elastomer particles did produce a marked local inflammatory response consisting mostly of macrophages and lymphocytes. Thus, the presence of an inflammatory response does not entail adjuvant activity. Both the gel/oil and elastomer particles produced an inflammatory effect, but only the gel/oil had any adjuvant effect. Furthermore, the only way of showing the adjuvant effect of the gel/oil is to homogenize it outside the body with a foreign material, BSA. Simply mixing antigen with gel/oil does not produce an adjuvant effect. Neither the large nor the small particles of the silicone elastomer potentiated antibody response in the rat model. Thus, any silicone elastomer particulates that might come off the Norplant implant would, similarly, have no adjuvant effect even though both large and small particles can incite a respectable inflammatory response.

Conclusions

These experiments indicate that there is no risk of developing autoimmune disease associated with implants of silicone elastomer.

Presentation 4 BIOCOMPATIBILITY AND MEDICAL APPLICATIONS OF SILICONE-BASED MATERIALS: REVIEW OF PERTINENT FINDINGS

James M. Anderson, M.D., Ph.D.

Case Western Reserve University

Background

This presentation summarizes what is known about those aspects of the silicone-based materials used in contraceptive implants that would permit



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