Figure 3. LTB₄ is required for MyD88 expression in phagocytes.

(A) MyD88, TIRAP, TRIF, and TIRP protein expression in WT macrophages and in 5-LO^–/– and BLT1^–/– macrophages treated for 24 hours with or without LTB₄. (B) Densitometry of MyD88 protein in 5-LO^–/– and BLT1^–/– macrophages. (C) Myd88 mRNA expression in 5-LO^–/– and BLT1^–/– macrophages treated as in A. (B and C) Data are representative of 3 experiments, performed in triplicate; values are relative to control WT macrophages (dashed line). *P < 0.05 versus WT; ^#P < 0.001 versus untreated 5-LO^–/–. (D) MyD88 protein expression in resident peritoneal (PM), alveolar (AM), and splenic (SM) macrophages as well as splenic DCs, T and B lymphocytes, and lung fibroblasts from WT and 5-LO^–/– mice. Data are representative of 3 experiments. (E) Myd88 mRNA decay in WT and 5-LO^–/– macrophages harvested after treatment with actinomycin D (2.5 mg/ml). Data are from 3 experiments in triplicate; values are relative to untreated macrophages from both genotypes. (F) MyD88 protein in WT and 5-LO^–/– macrophages incubated for 24 hours as indicated. Immunoblot results are from 2–3 independent experiments (relative MyD88 density shown by numbers beneath). Lanes were run on the same gel but were noncontiguous (white line). (G) Nitrite production in WT and 5-LO^–/– macrophages pretreated for 24 hours with or without LTB₄, followed by LPS for another 24 hours. Data are representative of 3 experiments. *P < 0.05 versus control; ^#P < 0.05 versus non–LTB₄-treated stimulated WT; ^&P < 0.01 versus LPS or IL-1β alone.