Fig. 2.
Direct cell-to-cell contact is a prerequisite for neutrophile-induced A549 proliferation. A549 cells were either directly co-incubated with neutrophils (7.5 × 106/ml) or neutrophils were placed in the upper compartment of 0.4 µM pore transwells and co-cultured with A549 cells grown in the lower compartment of 24-well cell culture plates. All co-cultures were stimulated with 0.1 µg/ml LPS. After 6 h, the neutrophil-containing cell supernatant or the upper compartment were removed, A549 cells were washed three times, and again incubated for 2.5 h with 500 µl fresh medium containing 75 µl MTS solution. Absorbance was read at 490 nm. Values are expressed as percentage of MTS activity of A549 cells in the absence of neutrophils, which was set to 100 %, as indicated by the horizontal dotted line. Horizontal bars indicate averages of six independent experiments, each performed in triplicates