Antibacterial system generated by lactoferrin in mice in vivo is primarily a killing system

A single dose of bovine lactoferrin (BLF) was given intravenously (i.v.) to CFW mice 24 hours (h) prior to the i.v. injection of the E. coli lethal dose (LD100). BLF strongly accelerated the clearance rate of E. coli from the blood as well as its killing rate in the liver, lungs, spleen and kidney. The highest clearing and killing rate was found 5 h after E. coli LD100 injection. The most intensive killing in the organs examined was found in the lungs and kidney. Analysis of organs of i.v. BLF-stimulated mice which survived up to day 30 after the infection by E. coli showed that not all animals were definitely pathogen-free. It was concluded that the defense system generated by BLF in mice in vivo is primarily a bacteria-killing one. The participation and cooperation of reticulo-endothelial (RE)-macrophages and granulocytes in the phagocytosis and killing of E. coli may thus be related to the protective activity of LF.