The effects of lactoferrin on myelopoiesis: can we resolve the controversy?

Lactoferrin (LF) is an iron-binding protein contained in the secretory fluids of mammals and secondary granules of neutrophils. LF is a key element in innate immunity and exhibits a wide spectrum of activity against pathogens. Although the effects of LF on the maturation and effector function of immune system cells are well recognized, its regulatory function on myelopoiesis has been a matter of controversy for a long time. The majority of early studies demonstrated the role of LF as a negative feedback regulator of myelopoiesis. There were also reports that revealed no significant involvement of LF in that process. However, a number of experimental data, together with clinical observations, indicate a stimulatory action of LF in myelopoiesis. The aim of this article is to review the available literature data regarding the effects of LF on myelopoiesis in mice and humans. Possible reasons for opposing views on this subject are presented.