Partial characterisation of the high and low molecular weight forms of P388D1-derived interleukin 1

The murine macrophage-derived cell line P388D1 secretes the lymphokine interleukin 1 (IL-1) when stimulated by a variety of agents. When stimulated by bacterial lipopolysaccharide (LPS) the cells release IL-1 in both high and low molecular weight (m.w.) forms. The proportion of high m.w. IL-1 is reduced when IL-1-containing supernatants are concentrated by ammonium sulfate precipitation subsequent to hollow-fiber filtration. The high m.w. form can be converted to the low m.w. form by proteolysis, reduction and alkylation, or chromatography in a dissociating solvent. The low m.w. form remains as such, even when reconcentrated in fetal calf serum-containing medium. The high m.w. form thus likely consists of a complex between low m.w. IL-1 and another protein secreted by the P388D1 cell line.