Lactoferrin (LF), a globular multifunctional protein with antimicrobial activity (bacteriocide, fungicide), is part of the innate defense, mainly at mucoses. Lactoferrin is found in milk and many mucosal secretions such as tears and saliva. Lactoferrin is also present in secondary granules of PMN and also is secreted by some acinar cells. Human colostrum has the highest concentration, followed by human milk, then cow milk.

Lactoferrin belongs to the transferrin family proteins (TF, melanotransferrin, ovotransferin, etc.). Its molecular mass is 80,000 u (80 kDa).Lactoferrin antimicrobial activity is due partly to its high affinity for Fe (ferric state). LF proteolysis produces lactoferricin, kaliocin-1 small peptides with antimicrobial activity.