Lactoferrin is an approximately 80 kDa glycoprotein which was first isolated from milk and found in epithelia and most body fluids and secretions. Lactoferrin is secreted in plasma by neutrophils. Its plasma concentration represents a positive relation to the total pool of neutrophils and the rate of neutrophil turnover. In inflammation lactoferrin is released from secondary granules of neutrophilic leukocytes into the extracellular medium. Therefore the extracellular lactoferrin concentration can be used as an index for neutrophil activation. Lactoferrin is able to strongly bind to iron and considered to have antibacterial properties. Human lactoferrin binds to bacterial products through its highly positively charged N terminus and kills various bacteria most probably by inducing intracellular changes in these bacteria without affecting the membrane permeability. Lactoferrin also plays a role in signal transduction, immunomodulation and has antiadhesive, anticancer, antiviral activity.