Interaction Of Lactoferrin Research Articles

Lactoferrin uptake and iron processing into macrophages: a study in familial haemochromatosis

Various properties of lactoferrin from neutrophils of normal individuals and patients with familial haemochromatosis were compared. No difference was found with respect to (1) the lactoferrin content of neutrophils, the molecular weight and isoelectric point of the protein, the dissociation of its complex with iron at acidic pH, its binding to isolated monocytes, and its uptake by the mouse reticulo-endothelial system. Macrophages from patients and controls were also found to be similar in their ability to bind and ingest lactoferrin and to process the iron provided by the protein. Therefore a defect in the interaction of lactoferrin with the reticulo-endothelial system, related either to the protein itself or to the cells, seems unlikely. A comparison of the lactoferrin- and the transferrin-mediated iron processing by monocytes is finally presented.

Interaction of lactoferrin and transferrins with the outer membrane of Bordetella pertussis.

Bordetella pertussis was able to grow in vitro under conditions where the only iron present was bound to the iron-binding proteins ovotransferrin, transferrin or lactoferrin. Under these conditions the bacteria produced neither hydroxamate nor phenolate-catecholate siderophores to assist in the procurement of iron. Examination of B. pertussis outer-membrane preparations by SDS-PAGE and immunoblotting showed that the iron-binding protein ovotransferrin was bound directly to the bacterial surface. Assays of the binding of radiolabelled transferrin by the bacteria showed that the association was a specific process and that there was turnover of the bound proteins. Competitive binding assays indicated that lactoferrin could be bound in the same way. It is suggested that B. pertussis obtains iron directly from host iron-binding proteins during infection.

Characterization of lactoferrin interaction with Streptococcus mutans.

Lactoferrin (LF) is an iron-binding glycoprotein common to exocrine secretions and the specific granules of neutrophils. Each molecule is capable of high-affinity coordinate-binding of two ferric ions with two bicarbonate or carbonic anions. The initial aspect of the present study was directed at determining the nature of anion involvement in LF bactericidal activity. It was found that selective anions were capable of inhibiting the expression of bactericidal activity by LF on S. mutans 10449. The ability to block LF expression was directly related to the capacity of the anion to serve as a coordinate ion in iron-binding by the transferrin molecules. These data support the hypothesis that the LF target site on the bacterial surface is anionic. There has been controversy in the literature regarding LF involvement in hydroxy radical generation. The second phase of these studies indicated that treatment of S. mutans with LF under anaerobic conditions abrogated the bactericidal effect of this molecule. LF-killing could be enhanced by the presence of thiocyanate and inhibited by catalase and lactoperoxidase; however, bovine serum albumin was equally effective as an inhibitor. The apparent requirement for oxygen in LF bactericidal effect on S. mutans is not inconsistent with a hydroxy radical mechanism.

Lactoferrin binds to neutrophilic membrane DNA.

Lactoferrin (LF) binding to the surface of human neutrophils was shown to be dependent upon the presence of cell surface DNA by (i) an abrogation of LF binding after treatment of whole cells with DNAse; (ii) an abrogation of LF binding to a purified cell membrane suspension after DNAse digestion, (iii) a restoration of LF binding, after initial treatment of cells with DNAse, by the addition of exogenous DNA. Using a biotinylated LF probe, no other binding molecules were found after SDS PAGE of neutrophil cell membrane proteins. Further evidence of a DNA-LF interaction was obtained by the co-isolation of LF with DNA by both gel chromatography and affinity chromatography using Heparin Sepharose CL 6B. The interaction of LF with neutrophils was a saturable phenomenon with a Kd of 6.2 X 10(-6) M and a maximum binding of 9.2 X 10(6) molecules per cell. These results suggest that cell membrane DNA may have a novel role as a receptor for LF, and indicates the need for further experiments to determine whether the functional effects of LF are modified by the DNAse treatment of LF responsive cells.

Interaction of lactoferrin, monocytes, and T lymphocyte subsets in the regulation of steady-state granulopoiesis in vitro.

Colony-stimulating activities (CSA) are potent granulopoietic stimulators in vitro. Using clonogenic assay techniques, we analyzed the degree to which mononuclear phagocytes and T lymphocytes cooperate in the positive (production/release of CSA) and feedback (inhibition of CSA production/release) regulation of granulopoiesis. We measured the effect of lactoferrin (a putative feedback regulator of CSA production) on CSA provision in three separate assay systems wherein granulocyte colony growth of marrow cells from 22 normal volunteers was stimulated by (a) endogenous CSA-producing cells in the marrow cells suspension, (b) autologous peripheral blood leukocytes in feeder layers, and (c) medium conditioned by peripheral blood leukocytes. The CSA-producing cell populations in each assay were varied by using cell separation techniques and exposure of isolated T lymphocytes to methylprednisolone or to monoclonal antibodies to surface antigens and complement. We noted that net CSA production increased more than twofold when a small number of unstimulated T lymphocytes were added to monocyte cultures. Lactoferrin's inhibitory effect was also T lymphocyte dependent. The T lymphocytes that interact with monocytes and lactoferrin to inhibit CSA production are similar to those that augment CSA production because their activities are neither genetically restricted not glucocorticoid sensitive, and both populations express HLA-DR (Ia-like) and T3 antigens but not T4 or T8 antigens. These findings are consistent with results of our studies on the mechanism of lactoferrin's inhibitory effect with indicate that mononuclear phagocytes produce both CSA and soluble factors that stimulate T lymphocytes to produce CSA, and that lactoferrin does not suppress monocyte CSA production, but does completely suppress production or release by monocytes of those factors that stimulate T lymphocytes to produce CSA. We conclude that mononuclear phagocytes and a subset of T lymphocytes exhibit important complex interactions in the regulation of granulopoiesis.

Interaction of lactoferrin with agar gels and with trypan blue

1. 1.Observations have been made on the interaction of purified human lactoferrin with one or more components of agarose gels. 2. 2.The protein has been found to enter into a firm combination with Trypan Blue. Studies of the dye-protein complex by electrophoresis, gel filtration, spectrophotometry and ultracentrifugation indicate that the combination occurs in a fixed molar ratio.