Lactoferrin: Its Role as a Regulator of Human Granulopoiesis?^a

Abstract

Lactoferrin has been proposed recently as a physiological regulator of the granulocyte-monocyte progenitor (CFU-GM). This glycoprotein, when saturated with iron, has been said to limit the CFU-GM growth by decreasing production and release of colony stimulating activity by monocytes and macrophages. Human milk lactoferrin saturated with iron, at concentrations ranging from 10(-8) M, was added either to endogenously stimulated bone marrow cells or to mononucleated cells used as feeder layers for adherent cell-depleted marrow. Irrespective of the concentration of lactoferrin within the culture system used, no significant inhibition of the CFU-GM growth was observed. Moreover, the CFU-GM stimulating activity of medium conditioned by a 4 day incubation of 1 X 10(6) mononucleated blood cells in the presence or in the absence of lactoferrin was the same. Various possible explanations for not confirming the reported inhibiting activity of iron-saturated lactoferrin were explored: (a) masking inhibition of the system by prostaglandin E2 (PGE2), (b) masking inhibition of the system by bovine lactoferrin present in the fetal calf serum, (c) preinhibition of the system by leukemic-associated inhibitory activity possibly present in the culture system, (d) the iron and calcium content of the culture medium used, (e) the fixation of lactoferrin to plastic compounds, (f) the source of the human lactoferrin used, and (g) the marrow cell separation methods used. None of these factors was shown to play a role in vitro in the activity of lactoferrin and thus no evidence was found for a significant role of lactoferrin in the regulation of human granulopoiesis.

Lactoferrin-lipopolysaccharide (LPS) binding as key to antibacterial and antiendotoxic effects

“…The effect of lactoferrin in promoting granulopoiesis apparently results from its ability to stimulate the increase in CSF production, as has been shown under in vitro and in vivo conditions [41]. However, the role of lactoferrin as modulator agent on granulopoiesis was not at all confirmed by some other studies [42,43]. These apparently divergent in vitro results may reflect the up-regulatory and down-regulatory in vivo role of Lf on myelopoiesis, in the first and last stages, respectively, of the inflammatory response during bacterial infection [44].…”

Lactoferrin as an Adjunctive Agent in the Treatment of Bacterial Infections Associated with Diabetic Foot Ulcers

“…This iron dependent suppressor effect of human lactoferrin, when tested in human bone marrow derived cells and blood monocytes, was linked to the decrease of GM-CSF (Broxmeyer et al, 1980). However, the role of lactoferrin as a modulating agent on granulopoiesis was not at all confirmed by some other studies (DelForge et al, 1985;Winton et al, 1981).…”

Global Perspective on Diabetic Foot Ulcerations

“…This iron dependent suppressor effect of human lactoferrin, when tested in human bone marrow derived cells and blood monocytes, was linked to the decrease of GM-CSF (Broxmeyer et al, 1980). However, the role of lactoferrin as a modulating agent on granulopoiesis was not at all confirmed by some other studies (DelForge et al, 1985;Winton et al, 1981).…”