RBP4 and chronic obstructive pulmonary disease: We found RBP4 recombinant protein, which was administered 4 h prior to P. aeruginosa inoculation, decreased the severity of airway inflammation in PA-COPD mice, including lower infiltrate scores, and reduced MPO activity, when compared with those PA-COPD mice injected with control BSA (Figures 6C, D).