Time course analysis of S. aureus clearance and leukocyte trafficking within the peritoneal cavity of WT and Fibγ ^390–396A mice following intraperitoneal infection. (A) Higher levels of S. aureus in Fibγ ^390–396A mice relative to WT animals were appreciable 30 minutes after inoculation, and obvious differential expansion was apparent after 3 hours. P < 0.02, Mann-Whitney U test (n = 5 pairs). (B) Representative microscopic views of peritoneal lavage cytospins prepared at the 3-hour time point from WT (left) and Fibγ ^390–396A mice (right). Bacterial phagocytosis (arrows) was found in both genotypes, but few residual bacteria were found within WT mice. In contrast, leukocytes from mutant animals appeared overwhelmed with bacteria, which often led to phagocyte disruption (double arrowhead). (C–F) Total cell counts and leukocyte differentials within peritoneal lavage fluid from WT and Fibγ ^390–396A mice. Unchallenged mice (C) displayed no significant genotype-related difference in resident cells (P – 0.5, Mann-Whitney U test using four pairs). Three hours after infection (D) a major increase in neutrophil levels was observed in mice of both genotypes compared with naive mice (compare panels C and D), with a trend toward fewer total cells and fewer neutrophils in mutant mice (P ♠ 0.1, Mann-Whitney U test using five pairs). However, comparison of WT and Fibγ ^390–396A mice challenged with heat-killed bacteria for 5 hours (E) or 24 hours (F) indicated that there was, if anything, an increase in total leukocyte and neutrophil accumulation in mutant mice (P > 0.2 for all comparisons between genotypes using a Mann-Whitney U test using five pairs). The data shown are means ± SD. Neut, neutrophil; Mac, macrophage.