Activation of macrophages by silicones: phenotype and production of oxidant metabolites

BACKGROUND: The effect of silicones on the immune function is not fully characterized. In clinical and experimental studies, immune alterations associated with silicone gel seem to be related to macrophage activation. In this work we examined in vivo, phenotypic and functional changes on peritoneal macrophages early (24 h or 48 h) and late (45 days) after the intraperitoneal (i.p.) injection of dimethylpolysiloxane (DMPS) (silicone). We studied the expression of adhesion and co-stimulatory molecules and both the spontaneous and the stimulated production of reactive oxygen intermediates and nitric oxide (NO). RESULTS: The results presented here demonstrate that the fluid compound DMPS induced a persistent cell recruitment at the site of the injection. Besides, cell activation was still evident 45 days after the silicone injection: activated macrophages exhibited an increased expression of adhesion (CD54 and CD44) and co-stimulatory molecules (CD86) and an enhanced production of oxidant metabolites and NO. CONCLUSIONS: Silicones induced a persistent recruitment of leukocytes at the site of the injection and macrophage activation was still evident 45 days after the injection.