FIG. 7.

All precursors of the GPI Pfα activate production of TNF-α. Macrophages were incubated for 24 h with GPI Pfα (α) or with its precursors Pfβ (β), Pfγ (γ), Pfδ (δ), Pfɛ (ɛ), Pfζ (ζ), Pfη (η), and Pfθ (θ). The supernatant obtained after GPI precipitation containing non-GPI species was added to macrophages 30 min before Pfα was added (α+S). The values are means ± standard deviations of triplicate samples in a representative experiment. (B) TLC scans of P. falciparum GPI precursors and of P. falciparum contaminating molecules (supernatant), showing their comigration with Pfγ to Pfθ. (C and D) The contaminant molecules migrating with Pfɛ, Pfζ, Pfη, and Pfθ, but not with Pfγ, inhibited production of TNF-α and IL-12 in macrophages (γS,ɛS, ζS, ηS, and θS were added 30 min before Pfγ, Pfɛ, Pfζ, Pfη, and Pfθ were added). Fraction 3, separated from the supernatant using LC-NH₂ and LC-WCX cartridges, inhibited production of TNF-α and IL-12 in macrophages (S3 was added 30 min before Pfα was added). Medium alone was used as a negative control (lanes M). (E) TLC of S3. Free fatty acids are rose-violet. Myristic acid (My) was used as a positive control.