The Roles of CD11/CD18 and ICAM-1 in Acute Pseudomonas aeruginosa-Induced Pneumonia in Mice

Neutrophil accumulation in response to Pseudomonas aeruginosa in the lungs is mediated through CD11/CD18. This study determined the roles of CD11a, CD11b, and intercellular adhesion molecule (ICAM)-1 in P. aeruginosa-induced pneumonia and compared the function of ICAM-1 using Abs or ICAM-1 mutant mice. Anesthetized BALB/c mice pretreated with either Abs against CD11a, CD11b, ICAM-1, or rat IgG received intratracheal instillation of P. aeruginosa for 4 h. In other studies, ICAM-1 mutant and wild-type mice received either anti-ICAM-1 Ab or rat IgG followed by instillation of P. aeruginosa. The data show that Abs against CD11a, CD11b, and ICAM-1 in BALB/c mice inhibited neutrophil emigration by 79, 81, and 56%, respectively. ICAM-1 mutant mice showed no inhibition of neutrophil emigration compared with wild-type mice. Pretreatment with anti-ICAM-1 Ab inhibited neutrophil emigration in wild-type (129/SvxC57) mice by 67% but had no effect in ICAM-1 mutant mice, suggesting that the Ab was acting specifically through recognition of its Ag. We conclude that CD11 a and CD11 b are required for neutrophil emigration. The observed function of ICAM-1 varies depending on the method by which it is inhibited. Abs may overestimate function by altering other cellular functions or mutant mice may develop alternative pathways of emigration.