Detection of an Inhibitor of Interleuken 1 Activity in Febrile Mouse Serum
McWatters, Ellen R.
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The Hypersensitivity Disease Research unit of the Upjohn Company is currently interested in developing a drug that would lessen or alleviate chronic arthritic pain. Several reports have indicated that Interleukin 1 (IL 1) may aid in, or cause the inflammation and tissue damage associated with chronic arthritis. Interleukin I is a polypeptide secreted by activated macrophages as well as other types of cells. Prolonged production of IL I may ultimately lead to increased tissue damage and inflammation associated with arthritis. Several reports indicate that the human body may produce a natural inhibitor of IL 1 while in the febrile state. It is known that injection of endotoxin lipopolysaccharide (LPS) into mice previously sensitized to Mvcobacterium bovis, strain BCG, will rapidly induce a febrile response which is probably mediated by IL 1. It seemed possible that a natural feedback inhibitor of IL 1 might be produced near the peak of the febrile response. CBA and C3H/HeJ strain mice were injected intraperitoneally (i.p.) with 10 live BCG organisms, followed three weeks later by an i.p. injection of 50 ug LPS. Serum was prepared from blood taken from these mice at various times after LPS injection. Normal serum was prepared from uninjected CBA and C3H/HeJ mice. Both sera were tested for IL 1 inhibitory activity by a modification of the IL 1 assay described by Gillis and Mizel (1981). The febrile serum inhibited IL 1 activity more than normal mouse serum. Both sera were fractionated by gel filtration on a column of 5ephacryl S-200 equilibrated in phosphate buffered saline. Each fraction was assayed for IL 1 inhibitory activity as indicated above. The inhibitory fractions from the febrile serum eluted near the void-volume corresponding to molecules greater than 150,000 daltons in molecular weight. The corresponding fractions from normal mouse serum were also inhibitory, but far less so than the febrile serum fractions. Further characterization of the inhibitor was made by fractionation of pooled inhibitory fractions from the Sephacryl S-200 gel on a DEAE-Sephacel ion exchange column and Protein A Sepharose gel. The search for an inhibitor of IL 1 proved to be successful. However, many possibilities as to the identity of the inhibitor(s) remain open, since a variety of conclusions could be drawn from the results.