Endogenous mediators of the acute-phase reaction. I. Rabbit granulocytic pyrogen and its chromatographic subfractions

LP, a saline extract of exudate-derived rabbit granulocytes, shown to be free of endotoxin contamination by sensitive LAL assay, can elicit brisk acute-phase responses in the rabbit. Following a single large intravenous dose of LP (875 mce) there is a brisk fall in serum iron at 8 hr and marked elevations in concentrations of CxRP, haptoglobin, fibrinogen, and ceruloplasmin and a lesser rise in sialic acid in the blood at 24 hr, which return toward baseline to varying degrees by 48 hr. When the crude LP solution is fractionated by column chromatography on Sephadex G75, all detectable acute-phase mediating activity elutes in a fraction (pool C) which contains all the pyrogenic activity and about 15% of the total eluted protein. Within the limitations of the methods employed, the acute phase stimulating activity and the pyrogenic activity of LP preparations appear to be closely linked.