Toll‑like receptor 2 promotes bacterial clearance during the initial stage of pulmonary infection with Acinetobacter baumannii.

Toll-like receptor 2 (TLR2) has been identified as a sensor for bacterial lipoprotein. To determine the role of TLR2 in host defense against Acinetobacter baumannii infection, wild-type (WT) and TLR2-deficient mice were infected intranasally with A. baumannii. Body weight, cytokine and chemokine levels in bronchoalveolar (BAL) fluid and lung histopathology were examined. Body weight changes in TLR2-deficient mice were comparable to those of WT mice throughout the experimental period. However, TLR2-deficient mice exhibited an increased bacterial load in the lungs and increased levels of interleukin-6 and chemokine (C-X-C motif) ligand 2 in BAL fluids compared with WT mice 1 day after infection. Histopathological features of lung tissue in WT and TLR2-deficient mice were comparable between WT and TLR2-deficient mice. Results of the present study demonstrate that TLR2 may have a minimal role in the host defense against A. baumannii at the early stages of infection.