FIG. 1.

The effect of meningococcal LOS structure on TNF-α release by human macrophages. Purified meningococcal LOS containing lipid A at a concentration of 0.56 pmol/ml (1 ng/ml) was used to stimulate 10⁶ differentiated U937 macrophages/ml overnight and assayed for TNF-α release. LOS from parent strain NMB and synA, lst, pgm, rfaK, gmhX, and kdtA mutants were used (Table 1). LPS from E. coli 0111:B4 was used as a control. As a control for cellular components retained by the purification procedure used to obtain LOS, a preparation from the LOS-deficient meningococcal mutant (lpxA) (Table 1) was used at 100 ng/ml (dry weight). Unstimulated macrophages incubated simultaneously were also used as control. Error bars represent SD from the mean, and the data are from eight independent determinations.