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.