| Popis: |
Response of vertebrates to bacterial lipopolysaccharide (LPS) may be regulated, in part, by serum factors that influence the bioavailability and cellular binding affinity of LPS. Using 3H- or 14C-labeled LPS, or a novel fluorescence-based assay for detection in CsCl isopycnic density gradients, our studies indicate the existence of factors in adult and fetal bovine serum that bind LPS. Within serum-containing gradients, labeled LPS appeared in two peaks: least-dense fractions (or = 1.30 g/cm3) and at 1.35 g/cm3. This profile was different from that of gradients without serum, where LPS appeared at 1.38 g/cm3. Binding of LPS to serum component(s) at 1.35 g/cm3 was rapid (1 min), saturable and specific. A partial shift (50%) of LPS from a density of 1.35 g/cm3 to other serum components ator = 1.30 g/cm3 occurred over 1 h. Flow cytometric analysis indicated that bovine serum factors influence the binding of LPS to blood monocytes, because monocyte-FITC-LPS association increased in the presence of bovine serum. |
