Proteose peptone–induced neutrophil accumulation in the peritoneal cavity in wild-type and laminin α4–deficient mice. Harvested neutrophil count in wild-type (WT) and LNα4-deficient (KO) mice treated with either phosphate-buffered saline (PBS) or proteose peptone (PP). Neutrophil peritoneal infiltration was induced by intraperitoneal injection of 3% proteose peptone and measured 6 hours after stimulation. Neutrophils accumulated in the peritoneal cavity were harvested and counted by flow cytometry. There were 8 WT and 8 KO mice analyzed (3 with PBS and 5 with PP for each group). Mean, SD, and P value (**P < .01) are shown. PMN indicates polymorphonuclear neutrophils.