Rap1 activation is not inhibited by PGE₂treatments. Neutrophils of a healthy donor were preincubated for 10 minutes with 100 μmol/L IBMX followed by 30 seconds of incubation with 30 μmol/L PGE₂. Cells were stimulated with 1 μmol/L fMLP, and Rap1 activity was measured after the indicated time points. As a control, untreated neutrophils were stimulated with the same amount of fMLP. Respiratory burst was measured to control for the functionality of the cAMP treatment. Representative examples of at least three independent experiments are shown.