Compartmentalization of the acute cytokine response in humans after intravenous endotoxin administration.

Lung cytokine production was examined after the intravenous administration of endotoxin to 23 normal human subjects. Bronchoalveolar lavage (BAL) was performed 7 days before and 1.5 or 5 h after endotoxin (4 ng/kg). Cytokine mRNA was evaluated in cell pellets (> 98% macrophages) by use of reverse transcription and the polymerase chain reaction. Immunoreactivity was measured by enzyme-linked immunosorbent assay of 20- to 40-fold concentrated BAL. Interleukin- (IL) 8 was detected in BAL (4-130 pg/ml) but not in the serum at baseline. Few neutrophils were found in BAL (< 1%) despite this IL-8 gradient. Peak serum IL-8 levels occurred 2 h after endotoxin (3,930 +/- 241 pg/ml), but BAL neutrophils and IL-8 did not increase. Peak serum tumor necrosis factor (TNF) levels occurred 1.5 h after endotoxin (1,844 +/- 210 pg/ml), but TNF was detected in only 1 of 20 BAL samples. TNF and IL-8 mRNA were detected by polymerase chain reaction in > 70% of the BAL samples before endotoxin, whereas IL-1 alpha, IL-1 beta, and IL-6 were detected in < 25% of the BAL samples. After endotoxin, no change was detected in cytokine mRNA expression. Actinomycin D treatment of the BAL did not alter the pattern of cytokine mRNA expression. These data suggest that mechanisms exist to insulate the alveolar space from the stimulatory effects of endotoxin and high circulating levels of cytokines. Additional factors appear to control the chemotactic effects of IL-8 on neutrophils in the air spaces during acute systemic inflammation.