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Lactoferrin, a granule-associated glycoprotein, is a cationic protein with a high proportion of arginine and lysine at the N-terminal region, with two glycosylation and several iron-binding sites. Lactoferrin is highly antibacterial against both gram-positive and gram-negative bacteria at concentrations ranging from 3 to 50 μg/ml. It is believed that these lethal effects are due to a direct interaction of lactoferrin with the cell surface and subsequent disruption of normal permeability functions of the membrane, a so-called dissipation of proton motive force action (23). Similarly, expression of an antimicrobial tachyplesin gene from Asian horseshoe crabs led to antibacterial activity against Erwinia spp. in transgenic potato (24).

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Lactoferrin was used in the fractionation of lactoperoxidase and lactoferrin from bovine whey using a cation exchange membrane. It was used in the determination of lactoferrin and immunoglobulin G in animal milks by new immunosensors.

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Lactoferrin is an iron binding protein. It is structurally similar to transferrin, the plasma iron transport protein; but lactoferrin has a much higher affinity for iron (250 fold). It is very abundant in colostrum and small amounts can also be found in tears, saliva, mucous secretions and in the secondary granules of neutrophils. It is made by mucosal epithelium and neutrophils and is released by these cells in response to inflammatory stimuli. Bacterial growth is inhibited by its ability to sequester iron and also permeabilize bacterial cell walls by binding to lipopolysaccharides through its N-terminus. Lactoferrin can inhibit viral infection by binding tightly to the viral envelope protein. This prevents cell-virus fusion by blocking the binding domain. Lactoferrin appears to activate host defense systems in part by stimulating the release of interleukin-8, a neutrophil activator. It may also be involved in antibody and interleukin synthesis, lymphocyte proliferation and complement activation.

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