The adjuvant effect of silicone-gel on antibody formation in rats

The extent of immunological adjuvancy of silicone-gel, from mammary implants, up to now, has not been determined definitively. This study compares the immune potentiation effects of silicone-gel with that of Freund's adjuvant, using bovine serum albumin (BSA) as the test antigen in rats. Sixty, 250 gr., male Sprague Dawley rats were divided into six groups: I- phosphate buffered saline (PBS) only, II- silicone oil (Dow Corning Medical Grade 360 liquid silicone), III- 50% silicone-gel (McGhan Medical Corp.- mammary implant) in silicone oil, IV- complete Freund's adjuvant (CFA), V- incomplete Freund's adjuvant (IFA), and VI- 50% silicone oil in IFA. Each adjuvant was mixed or emulsified with an equal volume of 50 micrograms of BSA in 150 microliters of PBS. Each immunization was given intramuscularly in a single injection. Cardiac puncture test bleeds were taken at 12, 22, 40 and 56 days post immunization and the serum anti-BSA-antibody was measured by ELISA. The results indicate that silicone-gel is a potent immunological adjuvant, compared to both CFA and IFA. Silicone oil alone is not as potent as adjuvant and seems to inhibit the immune response when mixed with IFA. There thus appears to be a distinct possibility that silicone-gel may also be able to mediate an auto-immune reaction.