Fig 4. A deficiency of TLR9 is resistant to stress-induced macrophage apoptosis TLR9 knockout mice or wild type BALB/c mice aged 6 to 8 weeks were subjected to a 12 h physical restraint daily.

After 2 d stress, mice were sacrificed by cervical dislocation, and the macrophages were harvested, purified and cultured (5 × 10⁵ cells/well) on culture plates for 24 hours. Apoptotic cells (dark brown color cells) were determined by TUNEL assay. Photographs of representative TUNEL-stained cells are shown at the top. Magnification 200×. The bar graph shows the percentage of apoptotic cells. Means and SEs were calculated from 7 mice per group. ^* p < 0.05, ^** p< 0.01 compared with indicated groups.