FIG. 5.

Lipid A mutants of N. meningitidis do not induce TNF-α, IL-12, and IL-6 production by WT and SR-A^−/− Mφ. (a) WT and SR-A^−/− Mφ were incubated with 44/76 or the lipid A mutant (44/76lpxA) in the presence or absence of 2F8 (15 μg/ml). SR-A-mediated ingestion is expressed as a percentage of WT fluorescence. The average fluorescence values for WT and SR-A^−/− Mφ incubated with 44/76, 44/76 plus 2F8, lpxA, and lpxA plus 2F8 were (459, 22); (93, 30); (1,050, 44); and (293, 155), respectively. (b) WT and SR-A^−/− Mφ were incubated with ethanol-fixed 44/76 or 44/76lpxA bacteria at 37°C. After 24 h, the culture supernatant was removed and centrifuged to remove particulate matter before cytokine ELISA. The average concentration of triplicate conditions is plotted; the results are from a single experiment but are representative of at least three similar assays. Note that cells incubated with culture medium containing PBS or culture medium alone did not stimulate the Mφ to secrete cytokines (not shown). The error bars indicate standard deviations.