Objective and Design: The purpose of this study was to compare chemotactic activity of IL-8 alone with that of IL-8 reacted with rabbit α-macroglobulins (αM) in vivo.¶Methods: Initially the binding of recombinant human IL-8 (rhIL-8) to rabbit αM was studied. ¹²⁵I-labeled rhIL-8 was incubated with αM, and electrophoresed on native 5% gels or SDS-polyacrylamide 4-20% gradient gels. Next, rhIL-8 or rhIL-8 bound to αM was administered via an endotracheal tube to rabbit's lungs.¶Treatment: An endotracheal tube was wedged into a segment of the lobe of each lung, and a sample instilled through the tube into this segment. After 4 h the lungs were lavaged.¶Results: rhIL-8 bound to αM retained its full chemotactic activity in vitro but exhibited a diminished ability to induce the influx of neutrophils into the rabbit lung.¶Conclusions: The data suggest that αM may facilitate IL-8 clearance from the lung.