Tumor necrosis factor. Alpha and beta subtypes appear in circulation during onset of sepsis-induced lung injury

Tumor necrosis factor (TNF) may be involved in the pathogenesis of acute lung injury (ALI) associated with septicemia. Therefore, we measured plasma TNF activity during sepsis and development of lung injury in a porcine model of ALI. Plasma samples were obtained from anesthetized saline-infused control pigs (n = 10) and those infused for 1 h with live Pseudomonas aeruginosa (10(8) organisms/ml, 0.3 ml/20 kg/min) (n = 16). TNF activity was measured in plasma using the L929 fibroblast cytolytic assay. L929 cytotoxicity caused by TNF-alpha or TNF-beta was determined in plasma by measuring the cytotoxicity neutralized by TNF antisera. No significant TNF activity was detected in control pig plasma. In septic pigs, TNF activity appeared in plasma 15 min after onset of septicemia and remained elevated throughout the experiment (6.1 +/- 10.2% to 80.0 +/- 5.0%, 15 and 300 min, respectively). The appearance of pulmonary arterial hypertension, increased lung water, decreased lung compliance, and deteriorating gas exchange was correlated with the rise in plasma TNF activity, which reached a peak at 90 to 120 min in septic pigs. Our results provide evidence that both TNF subtypes are present in plasma during septicemia. Anti-TNF-alpha and anti-TNF-beta neutralized TNF activity in whole septic plasma at 15, 30, and 45 min after onset of septicemia, and the antibodies blocked TNF activity in serially diluted septic plasma at all time points up to 210 min of sepsis. TNF activity in septic plasma at 210 to 300 min was not neutralized entirely by TNF antisera.(ABSTRACT TRUNCATED AT 250 WORDS)