Binding and ingestion of human lactoferrin by mouse alveolar macrophages

59Fe-labelled human lactoferrin was found to be preferentially ingested by mouse alveolar macrophages (MAM) when compared to 59Fe-labelled human transferrin. The cells bound and ingested 125I-labelled iron-saturated and iron-free lactoferrin. The latter was digested faster (t1/2 = 5.8 hours), however, than the iron-saturated compound (t1/2 = 10.5 hours). The constant elimination of the Fe-lactoferrin complex by alveolar macrophages could enhance the bacteriostatic effect of lactoferrin in the pulmonary secretions.