In vitro model of tolerization. PMN from healthy donors were first cultured over 24 hours in the presence or absence of increasing amounts of E coli LPS. Supernatants were obtained and fresh medium was added to the cells. PMN were further cultured for an additional 24 hours (24-48 h) in the presence or absence of increasing amounts of E coli. IL-8 was measured in the supernatants. The results are the mean of four different experiments; the mean of SEM was ±30%.