Urokinase-type plasminogen activator is important for the development of immune complex-mediated, but not C5a-mediated, neutrophilia. (a) Number of neutrophils in the peritoneal exudate of C57BL/6 (n = 12) and u-PA-/- (n = 12) mice 4 hours post injection of ovalbumin (OVA) intravenously and anti-OVA intraperitoneally. (b) Levels of KC and MIP-2 in peritoneal exudate fluid of C57BL6 (n = 8) and u-PA-/- mice (n = 8) 4 hours post OVA/anti-OVA injection, as measured by ELISA. (c) Total cell number in the peritoneal exudate 2 hours post intraperitoneal injection of C5a or immune complex (n = 6 per group). Values expressed as mean ± standard error of the mean. *P < 0.01, **P < 0.001, C57 vs. u-PA-/- mice.