Effects of LPS on macrophage fluid phase uptake. Murine clone 4-4 macrophages were stimulated with vehicle or different concentration of LPS for 45 minutes at 37°C and 5% CO₂in the presence of [³H]sucrose. Subsequently, the cells were placed on ice and washed, and accumulated radioactivity was determined by scintillation counting. Using the specific activity of the [³H]sucrose, fluid phase uptake was expressed as femtoliter per cells per minute. The results show the average and standard error of three different experiments, each experiment being the average of three independent determinations. The statistical significance of the difference between the unstimulated and stimulated value is indicated by stars, one star indicating a P value <0.05 and two stars indicating a P value <0.01 (Pvalues were obtained using an unpaired two-tailed heteroscedastic Student’s t-test on the original nine values on which the graph is based.). (A) Effects of different LPS concentrations on macrophage pinocytosis. (B) Effect of different LPS concentrations on TNF (500 U/mL)-stimulated pinocytosis. (C) Effects of LPS in the presence of the CD14-blocking antibody rmC5-3. (D) Effects of LPS in the presence of an irrelevant antibody (SUK5).