ASSESSMENT OF THE LYMPHOCYTE-RESPONSE TO SILICONE

The biocompatibility of silicone is once again the focus of increased interest. Long considered inert, silicone has now been reported to be responsible for macrophage inhibition in rats and to possibly cause adjuvant disease in humans, and the related compound silica has elicited an antibody response in mice. The present study evaluates lymphocytic response to silicone as expressed by the demonstration of immunologie memory, or changes in specific lymphocyte subpopulations. Thirty-six female Lewis rats (250 gm body weight) were used as test animals. Group 1 (n = 12) was injected subcutaneously with 2.5 ml Freund’s Complete Adjuvant (FCA) alone. Group 2 (n = 12) was injected with 2.5 ml FCA sonicated with silicone gel. Group 3 (n = 6) was injected with 2.5 ml FCA, and at 4 weeks, gel-filled silicone implants were placed subcutaneously. Group 4 (n = 6) was injected with 2.5 ml FCA sonicated with silicone gel, and gel-filled silicone implants were placed at 4 weeks. An additional group of six rats (group 5) served as control for the experimental animals, and a group of four rats (group 6) served as naive control. Groups 1 and 2 were sacrificed at 4 weeks, and splenic lymphocytes were obtained for lymphocyte transformation assays performed against silicone. Assays also were run with the addition of the known mitogene Con A, PHA, LPS, and pokeweed. Cytofluorographic analysis of pan-T, T-helper, T-sup-pressor, and B-cell populations was performed. Groups 3, 4, 5, and 6 were harvested at 8 months, and splenic lymphocytes were subjected to lymphocyte transformation assay. No evidence of host sensitization to silicone either by the lymphocyte transformation assay or by changes in lymphocyte subpopulations was demonstrated. In this model, there is evidently no measurable systemic lymphocytic recognition or memory expressed with respect to silicone. © 1990 American Society of Plastic Surgeons.