Serum neopterin levels following intravenous endotoxin administration to normal humans.

Endotoxin was administered intravenously to five normal subjects. Measurement of serum neopterin levels demonstrated no significant change from baseline during the first 6 h after endotoxin administration, but were elevated two to four-fold at 24 h. In the three subjects in whom it was measured, a two-fold rise of the mean serum neopterin levels persisted at 48 h. The acute inflammatory events initiated by endotoxin administration to normal humans result in a delayed, but sustained, rise in serum neopterin levels which persists well after the acute phase response has subsided.