MONOMERIC RE LIPOPOLYSACCHARIDE FROM ESCHERICHIA-COLI IS MORE ACTIVE THAN THE AGGREGATED FORM IN THE LIMULUS AMEBOCYTE LYSATE ASSAY AND IN INDUCING EGR-1 MESSENGER-RNA IN MURINE PERITONEAL-MACROPHAGES

Using the equilibrium dialysis apparatus, an aqueous suspension of pre dominantly aggregated Re lipopolysaccharide (ReLPS) from Escherichia c oli D31 m4 (99.9% at 82.5 muM) can be processed to yield a solution of monomeric ReLPS at a saturation concentration of 77 ng/ml (3.4 x 10(- 8) m). We compared the in vitro biological activities of these two phy sically distinct types of ReLPS preparations in two select assays, rea ction in the Limulus amebocyte lysate (LAL) assay and induction of Egr -1 mRNA in macrophages. These assays were chosen for their rapid respo nse times and relatively short incubation periods. The monomeric ReLPS was 179- and 1000-fold more active than the aggregated ReLPS preparat ion in the LAL assay and induction of Egr-1 mRNA by thioglycollate-eli cited murine peritoneal macrophages, respectively. These results clear ly showed that the monomeric ReLPS is the more active form. The lower biological activities of the aggregated ReLPS preparation might be due to the presence of a small amount of monomeric ReLPS (0.01-0.6%) prod uced during its preparation and the incubation periods in the biologic al assays. Thus, aggregated ReLPS may be relatively inactive.