Fig. 1.

Peritoneal macrophages were pretreated with anti-tumour necrosis factor (TNF)-α, soluble TNF receptor or saline for 15 min and incubated with lipopolysaccharide (LPS) 20 ηg/ml for 20 h. Then, cells were washed and restimulated with LPS 100 ηg/ml for 6 h. Supernatants were collected and the biological activity of TNF-α was determined by L-929 assay. Results are expressed as the mean ± standard error of the mean (% control) of six independent experiments. *P < 0·05, significantly different from control. The control cells were treated only with LPS 100 ng/ml for 6 h and their TNF-α activity was considered as the 100% and is represented by a dashed line.