Lipopolysaccharide-Induced Elaboration of Interleukin 1 by Human Monocytes: Use for Detection of Lipopolysaccharide in Serum and the Influence of Serum-Lipopolysaccharide Interactions

An assay of interleukin 1 (IL-1) production by human monocytes was used to detect minute amounts of bacterial lipopolysaccharide (LPS) in sera or serum components designed for use in experiments or for injection into humans. Elaboration of IL-1 is a more sensitive criterion for the presence of LPS than is the rabbit pyrogenicity assay, and contamination of a given solution with LPS can be semiquantitatively determined by comparison with a standard. Interaction of (exogenously added) LPS with serum interferes with the recognition of LPS by monocytes but in a manner different from that encountered in the limulus test. Recognition of LPS by monocytes was not affected by the presence of naturally occurring antibodies to LPS. With use of IL-1 elaboration as an indicator, the presence of functionally active LPS in the sera of some patients with sepsis could be demonstrated.