Randomly selected white rabbits of both sexes, weighing 2.65 to 3.40 kg were divided into an experimental and control groups, and the experimental animals were injected with a bovine Fe ions free lactoferrin. The injection caused a drop of Fe ion level in the blood plasma. Twenty-two hrs later rabbits of both groups received a lethal dose of living cells of E. coli. After administration of E. coli the experimental rabbits survived 0.5 to 30 days, while those from the control group lived only 10 to1375 36 hrs. The injection of lactoferrin stimulated the natural defence system in rabbits against E. coli, by removing the Fe ions from the blood plasma and also by blocking their flow from c