Impairment of neutrophil emigration in CD18-null mice

This study was undertaken to investigate the requirement of Pz-integrins (C D11/CD18) for extravasation of neutrophils in mice. After intraperitoneal t hioglycollate injection, an in vivo model of inflammation, leukocyte extrav asation into the peritoneal cavity was studied in CD18-deficient and wild-t ype control mice. Before the induction of peritonitis, total and differenti al leukocyte counts in the circulation were analyzed and found to be 10-fol d elevated in CD18-deficient animals compared with wild-type animals. This was largely due to neutrophilia, with a 30-fold increase in neutrophil coun ts. In CD18-deficient animals, extravasated white blood cells in the perito neal cavity were diminished by 46%. The neutrophil number in the peritoneal fluid was severely reduced to 13% compared with control animals. In contra st, the number of emigrated monocytes was enhanced and lymphocyte emigratio n was not altered in the absence of CD18. The emigration efficiency of the neutrophils, calculated as ratio of the cell number in the lavage fluid and the circulating blood, was reduced to 0.4% in CD18-deficient mice compared with wildtype animals. Thus efficient neutrophil emigration into the perit oneal cavity strongly required CD11/CD18.