Priming of Rac2^-/- neutrophils fails to reverse the degranulation defect. WT and Rac2^-/- BMNs were stimulated with CB/fMLP (5 μM) with or without preincubation of 50 ng/mL TNF for 5 minutes. (A) MPO release from WT and Rac2^-/- BMNs in the presence or absence of TNF preincubation. ^***P < .01 compared with TNF-preincubated WT controls at the same doses of fMLP. (B) Phosphorylation of p38 MAP kinase in Rac2^-/- neutrophils is normal in response to TNF and CB/fMLP. Western blot analysis was carried out for phospho-p38 and p38 MAP kinase in cellular lysates. (C) PENs were treated with increasing doses of fMLP 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. ^***P < .01. Error bars indicate SEM.