Lactoferrin is a 703-amino acid glycoprotein originally isolated from milk. Plasma lactoferrin is predominantly neutrophil derived but indications are that it may also be produced by other cells. Lactoferrin in body fluids is found in the iron-free form, the monoferric form and in the diferric form. Three isoforms of lactoferrin have been isolated, ie two with RNase activity (lactoferrin-beta and lactoferrin-gamma) and one without RNase activity (lactoferrin-alpha). Receptors for lactoferrin can be found on intestinal tissue, monocytes/macrophages, neutrophils, lymphocytes, platelets, and on certain bacteria. A wide spectrum of functions are ascribed to lactoferrin. These range from a role in the control of iron availability to immune modulation. More research is necessary however to obtain clarity with regard to the exact mechanism of action of lactoferrin.