CD18 ADHESION BLOCKADE DECREASES BACTERIAL CLEARANCE AND NEUTROPHIL RECRUITMENT AFTER INTRAPULMONARY ESCHERICHIA-COLI, BUT NOT AFTER STAPHYLOCOCCUS-AUREUS

Leukocyte emigration in the lung occurs by both CD18-dependent and -in dependent mechanisms that are stimulus specific. We examined the effec t of CD18 blockade (mAb 60.3) on neutrophil (PMN) emigration into, and bacterial clearance from, the lung. After intravenous treatment wish either mAb 60.3 or saline, rabbits were given an intralobar inoculatio n with 10(9) colony-forming units of either Staphylococcus aureus or E scherichia coli. Four hours after inoculation, lungs were lavaged to a ssess PMN emigration, CD18 blockade reduced PMN emigration to E. coli by 16% but only 45% to S. aureus. Experiments to determine bacterial r ecovery from the lungs at 4, 8, and 24 h after inoculation showed that CD18 blockade impaired the early (4 h) clearance of E. coli but not S . aureus. These findings suggest that PMN emigration to intrapulmonary S. aureus is largely CD18-independent. In contrast, intrapulmonary E. coli elicits CD18-mediated PMN emigration, CD18 blockade results in i mpaired clearance of E. coli but not S. aureus from the lung.