Development and use of a radioimmunoassay for human interleukin-1 beta

Interleukin-1 (IL-1) mediates immunological, physiological, and metabolic changes associated with inflammation and host defense systems. Measurement of IL-1 activity can vary with the bioassay employed and substances have been described in several bioassay systems that either inhibit or mimic IL-1 activity. We now report a sensitive, rapid (24 hour), and specific radioimmunoassay for human IL-1 beta. Using 125I-labeled IL-1 beta and polyclonal rabbit antisera raised against recombinant human IL-1 beta, a competitive inhibition assay is described which detects 250 pg/ml of recombinant human IL-1 beta and 500 pg/ml of pI 7 human monocyte IL-1. The assay does not detect human IL-1 alpha, human interleukin-2, human tumor necrosis factor-alpha or human interferon-gamma. Nearly 100% of IL-1 beta added to human serum or urine can be quantitatively recovered. Substances such as fetal calf serum, phytohemagglutinin, opsonized Staphylococcus albus or E. coli endotoxin do not affect the assay. Using this assay, IL-1 beta was measured in both the intracellular and extracellular compartments of stimulated human blood mononuclear cells. These results were unaffected by the presence of substances that interfere with bioassays for IL-1 such as indomethacin or BW 755C, a lipoxygenase inhibitor. These studies establish the usefulness of quantitating immunoreactive human IL-1 beta produced by human blood cells and that which may be present in human body fluids in the presence of other cytokines.