摘要Objective: Being considered as a bridge between the innate immunity and acquired immunity, Toll-like receptors (TRLs) are very important innate immunity moleculars. Recent researchs on the innate immunity have focused on the relation- ship between TLRs and human tumor. This paper investgated the expression and significance of TLR9 in human pulmonary adenocarcinoma cell (A549 cell) and human bronchial epithelial cell (HBE cell). Methods: After culturing A549 cell and HBE cell in vitro, the expression of TLR9 mRNA and protein in both cells were detected by immunocytochemistry, Real-time Quantitative Reverse Transcriptase-Polymerase Chain Reaction (Real-time Quantitative PCR) and Western blot, respectively. Results: By immunocytochemistry staining, TLR9 was mainly expressed in both cells' cell membrane and endochylema as brown-yellow material. It showed that the expressions of TLR9 mRNA and protein in A549 cell were stronger than those in HBE cell (P < 0.01). Conclusion: The results suggest TLR9 might cause the progression of human pulmonary adenocaroinoma, and the mechanism needs to be further investgatied.