Compartmentalized roles for leukocytic adhesion molecules in lung inflammatory injury

By using the model of acute injury caused by intrapulmonary deposition of IgG immune complexes, blocking mAb to CD11a, CD11b, L-selectin, and intercellular adhesion molecule-1 (ICAM-1) were administered either i.v. or intratracheally (i.t.). The effects of these interventions were assessed according to lung injury, lung content of myeloperoxidase (MPO), TNF-α, and cellular content in bronchoalveolar lavage (BAL) fluids, and up-regulation of pulmonary vascular ICAM-1. In animals treated i.v. with Abs to CD11a, L- selectin, or ICAM-1 lung injury was significantly attenuated in parallel with reduced lung content of MPO. Under similar conditions, treatment with anti- CD11b had no effect. However, when the same mAb were administered i.t., anti- CD11 a and anti-L-selectin were without protective effects, whereas i.t. administered anti-CD11b and anti-ICAM-1 were each highly protective. The protective effects of anti-CD11b were related to profound reductions in BAL levels of TNF-α, pulmonary vascular up-regulation of ICAM-1, and lung content of MPO. The protective effects of i.t.-administered anti-ICAM-1 were not associated with reduced BAL levels of TNF-α. Protective effects of mAb were also reflected in reductions of retrievable neutrophils in BAL fluids. mAb to rat CD11b and CD18 but not to rat CD11a suppressed in vitro production of TNF-α by immune complex-stimulated rat alveolar macrophages. The mAb did not reduce NO₂^-/NO₃^- generation in stimulated macrophages but all mAb (except anti-ICAM-1) reduced O₂^- responses in macrophages. These data suggest a compartmentalized role for adhesion molecules in lung inflammatory injury after intraalveolar deposition of IgG immune complexes, with CD11a, L- selectin, and ICAM-1 being important in the vascular compartment for neutrophil recruitment, whereas in the alveolar compartment CD11b and ICAM-1 (but not CD11a and L-selectin) seem to play key roles.