Intraperitoneal administration of IL-33 causes neutrophil influx in C57BL/6 mice. (A) Wild-type C57BL/6 mice were injected intraperitoneally with PBS or 0.1 μg IL-33 and peritoneal cells were analyzed 6 hours later by flow cytometry. Neutrophils are represented by a Ly-6G⁺ population (a neutrophil specific clone of the Ly-6G antibody was used: 1A8), mast cells by a c-Kit⁺ population, macrophages by a CD11b^high population and B cells by a CD19⁺ population. (B) Quantification of panel A; results are presented as percentage of total peritoneal cells in peritoneal lavage obtained from injected mice. In panel A, representative plots are shown. Values are presented as mean ± SEM (n = 4-5) **P < .01. ns = not significant.