Effects of E coli and adenosine on IL-10 and IL-6 production by TLR4 WT and KO macrophages. (A) Adenosine synergizes with heat-killed E coli to up-regulate IL-10 production in both TLR4 WT and KO macrophages. Peritoneal macrophages were obtained from TLR4 KO and WT mice and were treated with heat-killed E coli (at a macrophage:bacterium ratio of 1:15) or E coli plus 100 μM adenosine for 5 hours, after which procedure IL-10 production was determined from the supernatant. ***P < .001 vs. corresponding E coli-treated group. ^###P < .001 vs. corresponding E coli-treated groups. ^##P < .01 vs. TLR4 WT group. (B) Effect of adenosine and E coli on IL-6 production. IL-6 levels were determined from the same supernatant that was used for measuring IL-10 production. ^###P < .001 vs. corresponding TLR4 WT groups, **P < .01 vs. E coli-stimulated group. (C) S aureus (at a macrophage:bacterium ratio of 1:15) stimulates IL-10 levels, which is enhanced by adenosine. The enhancing effect of adenosine on S aureus–stimulated IL-10 production is reversed by the A_2A receptor antagonist ZM241385. Peritoneal macrophages were obtained from CD-1 mice. IL-10 production was measured after 5 hours of stimulation with S aureus and/or 100 μM adenosine. ***P < .001 vs. S aureus alone. ^###P < .001 vs. 100 μM adenosine. (D) Lipoteichoic acid prepared from S aureus stimulates IL-10 release by CD-1 mouse peritoneal macrophages, which is enhanced by adenosine. Peritoneal macrophages were obtained from CD-1 mice and treated with 1 μg/mL lipoteichoic acid prepared from S aureus or lipoteichoic acid prepared from S aureus plus 100 μM adenosine for 5 hours, after which IL-10 release was determined from the supernatant. *P < .05 vs. control and ***P < .001 vs. control. Results (mean ± SEM) shown are representative of at least 3 experiments with n = 6 in each experiment.