Rap1 activation in resting and primed neutrophils. Rap1 activity is measured in primed and resting neutrophils. Neutrophils were primed by 20 minutes of 0.1 nmol/L GM-CSF stimulation. Subsequently, resting and primed neutrophils were stimulated with 1 μmol/L fMLP for the indicated time points. (A) Oxygen consumption was measured with a Clark oxygen electrode. (B) Rap1 activation was measured in neutrophils from the same donor as (A). Representative examples of at least three independent experiments are shown.