FIGURE 6.

Inhibition of phagosomal acidification but not oxidative burst enables macrophages to produce inflammatory cytokines in response to malaria parasites. BMDMs were incubated with P. falciparum IRBCs in the presence of theophylline (A), bafilomycin A₁ (B), or mixture of 5 nm of bafilomycin and 10 or 100 μm theophylline (C). Th, theophylline; BA1, bafilomycin A₁. TNF-α released into culture medium was analyzed by ELISA. Values for treatment with theophylline and/or bafilomycin A₁ in medium (control), all values in A, and some values in B and C are below the detection limit. D, BMDMs in 24-well plates were incubated with IRBCs in the absence and presence of bafilomycin A₁ (5 nm), theophylline (100 μm), and a mixture of bafilomycin A₁ (5 nm) and theophylline (100 μm). The cells were stained with anti-mouse CD11b followed by intracellular staining with anti-mouse IL-12 antibodies and analyzed by flow cytometry. The results of a representative of three independent experiments each performed in triplicate are shown. E, plots of mean values ± S.D. of the experiment shown in D. *, p < 0.05; **, p < 0.01; ***, p < 0.001.