Figure 3.

Exocytosis of secondary and tertiary but not primary granules following costimulation. Neutrophil degranulation 9 minutes after costimulation with 2 μM PF4 and 10 μg/mL anti-PF4 Ab (197.3) was measured by quantifying the release of (A) myeloperoxidase (primary granule), (B) lactoferrin (secondary granule), and (C) gelatinase B/MMP-9 (tertiary granule). Degranulation (mean ± SEM; n = 3) is expressed as percentage release of total neutrophil granule content. IV.3 blocks lactoferrin and gelatinase B release. *P < .01, with respect to all other treatments.