Short-term macrophage interleukin-1 response to injected silicone in a rat model

The short-term effects of silicone particles on the ability of splenic and peritoneal macrophages to produce Interleukin-1 (IL-1) were assessed. Lewis rats were divided into three groups. Group 1 animals (n=12) were injected subcutaneously with 2.5 ml of sterile saline; Group 2 animals (n=12) received 2.5 ml of Freund's Complete Adjuvant (FCA); Group 3 animals (n=12) received subcutaneous injections (2.5 ml) of a sonicated slurry comprised of equal parts of FCA and silicone. At days 1, 4, and 7 single-cell suspensions of splenic (10(8) cells/ml) and peritoneal (10(6) cells/ml) macrophages of four animals from each group were prepared. The supernatants from macrophages cultured in the presence or absence of lipopolysaccharide (LPS) were added to IL-1 dependent mouse thymocytes for 72 hrs, and subsequently pulsed with 3H-thymidine. Radioactivity incorporation was determined after 18 hrs. Peritoneal macrophage culture supernatants had significantly higher activity than splenic macrophages and all macrophages stimulated with LPS had significantly higher activity. At days 1 and 7, there were no significant differences in 3H-thymidine uptake. At day 4 there was an elevation of 3H-thymidine uptake from supernatant of peritoneal macrophages treated with FCA/silicone suggesting subcutaneous silicone injection has short-term effects.