Tissue expression of TLR5. (a) Constitutive expression of TLR5 mRNA (RT-PCR) in mouse lung, liver, gut and kidney. C-, negative control (no RNA); C+, positive control of the TLR5 primer kit. Sizes of the amplified fragments were 310 base pairs for positive control and 381 base pairs for TLR5. GAPDH, loading control. (b) Quantitative TLR5 mRNA expression in mouse lung, liver, gut and kidney. In each organ, TLR5 mRNA was normalized to the levels of 18 S. The expression of TLR5 is shown relative to the kidney, and is indicated above each column. (c) TLR5 protein expression was determined by immunoblotting with β-actin shown as a loading control. (d) Expression of TLR5 protein (immunoblot) in the lung under baseline conditions (0 h), and one (1 h) and three (3 h) hours after the administration of flagellin (5 μg). There was no evidence of TLR5 induction upon flagellin. Results, shown in duplicates, are representative of at least three independent experiments.