Neutrophil apoptosis in pathogenic IgG-injected Mac-1-deficient mice. WT and Mac-1 KO mice were injected intradermally with pathogenic anti-mBP180 IgG R530. The animals were examined 2, 4, and 24 hours after IgG injection for neutrophil apoptosis by detection of active caspase 3, an apoptosis effector enzyme. (A) Indirect IF showed significantly lower numbers of apoptotic neutrophils in the skin of Mac-1 KO mice than in WT mice. (B) Quantification revealed a significant decrease in the number of active caspase 3-stained neutrophils in the skin of Mac-1 KO relative to WT mice. Data shown are the mean ± SEM. n = 6, ^*P < .01.