Figure 2.

Injection frequency-dependence of orientational changes for neutrophils exposed to temporally decreasing FMLP concentrations. The time between sequential injections of FMLP is shown at the abscissa whereas the number of cells is given at the ordinate. The angles of cell reversals are shown for 0 ± 15° (no change or reversal in polarization direction) (striped bars), 45 ± 15° (solid bars), 90 ± 15° (open bars), and 180 ± 15° (dotted bars). A total of 50 cells was measured for each time point. Data for the 0 time interval are for chemokinesis at 10⁻⁸ M FMLP. Experiments were performed on 3–19 separate days. Significant differences were found among these populations (see text). These results show that the 10-s injection period was effective in reversing cell orientation by 180°.