Human interleukin 1. Purification to homogeneity.

Abstract

Human interleukin 1 (IL-1) was purified to homogeneity by a simplified procedure that results in excellent yields of pure material that retains a high level of biological activity. IL-1, secreted by human peripheral blood macrophages that were stimulated with Staphylococcus aureus, was purified by ion exchange chromatography and affinity chromatography on Procion Red agarose. The pure protein has a specific activity of 3.2 .times. 108 U/mg in the thymocyte mitogenesis assay and is pyrogenic. No MW heterogeneity was observed, in contrast to findings for mouse IL-1 and earlier reports of human IL-1. Purified IL-1, as analyzed by 2-dimensional electrophoresis/electrofocusing gels, exhibited a series of charged species with isoelectric points ranging from 6.0 to 4.9, all with a MW of .apprx. 17,500. Amino acid analysis indicated an abundance of acidic residues, in agreement with the low isoelectric points. There is little or no cysteine in the molecule. No evidence was found for the presence of carbohydrate moieties. The overall yield for this procedure was .apprx. 31% of the activity contained in the initial culture supernatant.