In vivo inhibition of neutrophil function in the rabbit using monoclonal antibody to CD18

The CD11b/CD18 membrane antigen complex has been shown to be essential for normal neutrophil function in vitro, and patients lacking this antigen exhibit severe neutrophil dysfunction. Murine monoclonal antibody 60.3 (Ab 60.3), directed toward CD18, is a potent inhibitor of human neutrophil function in vitro. To determine whether Ab 60.3 might similarly inhibit neutrophil function in vivo, we measured the effect of antibody administration on neutrophil localization to polyvinyl sponges placed s.c., in rabbits. Studies in 25 animals showed that infusion of Ab 60.3 at the time of sponge insertion resulted in dose-dependent inhibition of in vivo neutrophil migration with almost complete paralysis of neutrophil migration at higher antibody doses. These studies confirm the functional relevance of CD18, demonstrate that neutrophil function can be profoundly inhibited in vivo by Ab 60.3, and suggest that substances such as AB 60.3 may be clinically useful as potent anti-inflammatory agents.