Analysis of the inflammatory exudate surrounding implanted polymers using flow cytometry

Cellular, responses to silicone and latex were investigated using flow cytometry, to determine the cells involved in the inflammatory responses and to characterize the differences in the response between these materials, if any. A panel of 11 monoclonal antibodies were selected to cover the range of cells that could be involved in the response, each antibody being directly conjugated with fluorescein isothiocyanate (FITC). The materials were implanted subcutaneously into rats in tubular form; the tubes were sealed at one end with Silastic adhesive. Two tubes per animal were implanted, using four animals per time period for 1, 2, 5 and 7 day implantation periods. After these times the animals were sacrificed and the tubes retrieved and then spun to harvest the exudate from the lumen. This exudate was analysed using flow cytometry. Significant and reproducible differences in cell number and antibody positivity were observed between these two materials. Latex had a much larger cellular response and showed significant increases in antibody positivity that involved macrophages or granulocytes of unusual size and granularity. Overlap between antibody positivity made specific characterization difficult and led to many questions about the effect of exposure to a material and its effect on cell morphology and phenotype, particularly in the case of macrophages.