IL-6 levels in supernatants of stimulated H-CL (P5) fibroblast cultures. E. coli LPS (1 μg/ml), P. gingivalis LPS (1 μg/ml), rhIL-6 (5 ng/ml), rhTNF-α (5 ng/ml), rhIL-1α (100 pg/ml), rhIL-1β (5 ng/ml), or IL-1α (100 pg/ml) plus TNF-α (5 ng/ml) was added to confluent HGF H-CL cultures and incubated for 24 h, and supernatants were assayed for IL-6 levels by ELISA. Bars indicate SDs.