Immunogenic potential of carpal implants

This study investigated whether a cellular or a humoral-mediated immunologic response to silicone carpal prostheses could be detected in animals previously sensitized to silicone. Silicone carpal prostheses were emulsified in Freund's complete adjuvant (FCA). This emulsion was injected into guinea pigs weekly for 6 weeks. Controls received only FCA. Four weeks later a carpal prosthesis was implanted. Histology showed the implanted prosthesis encapsulated by fibrous tissue in sensitized animals, with a mononuclear infiltrate within the fibrous periprosthetic capsule consistent with a cellular immune response. Skin testing of the sensitized animals showed a true correlate response to the silicone antigen challenge, whereas no response was observed in the control group. The passive cutaneous anaphylaxis reaction in sensitized animals was positive, emphasizing that the antigen-antibody response was passively transferred. Tissue adjacent to the silicone implant in sensitized animals revealed an IgG deposition around the silicone particles by the fluorescent antibody technique. Control animals showed none of these reactions. These results indicate that microparticulate matter from carpal implants can possibly initiate both a cellular immunologic response and the production of a circulating antibody.