Figure 1.
TNF pretreatment suppresses induction of pro-inflammatory cytokines on secondary challenge by LPS. (a) Experimental design. (b) Human primary macrophages were stimulated with LPS (10 ng/ml) or TNF (10 ng/ml) for the indicated times and challenged with 10 ng/ml LPS for 24 hr. IL-6 in culture supernatants was measured by ELISA. (c) Percent tolerization of IL-6 was calculated by dividing IL-6 production of tolerized (LPS- or TNF-pretreated) cells by that of non-tolerized cells. Data are a summary of 27 independent donors. P values were calculated by paired Student’s t-test. ***, P < 0.0001 (d) Human primary macrophages were stimulated with LPS (10 ng/ml) or TNF (10 ng/ml) for 24 hr and challenged with 10 ng/ml LPS for 1 hr (TNF, IL-1β, iNOS and RANTES) or 3 hr (IL-6 and FPR1). Real-time PCR was used to measure mRNA levels. Data are representative of four independent donors (mean ± s.d. of triplicate determinations).