Absence of primary granule release in chemoattractant-stimulated Rac2^-/- neutrophils. Freshly prepared BMNs from WT and rac2^-/- neutrophils were examined for their ability to release the primary granule marker MPO in response to increasing doses of fMLP (A) for 15 minutes following 5 minutes preincubation with 5 μg/mL CB. MPO release was determined and shown as percentage of total cellular lysate values. (B) Neutrophils were stimulated with increasing doses of LTB₄ for 1 hour following 5 minutes preincubation with 5 μg/mL CB. (C) Elastase activity in supernatants of neutrophils stimulated with CB/fMLP. ^*P < .05. ^**P < .02. ^***P < .01. Error bars indicate SEM.