Human macrophage maturation in vitro: expression of functional transferrin binding sites of high affinity

Human blood monocytes (mo) when cultured in suspension on hydrophobic teflon membranes undergo terminal maturation to macrophages (MO). Together with the appearance of new lineage-restricted differentiation antigens, mature MO but not blood mo, express transferrin (TF) receptor molecules as detected...

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Bibliographic Details
Published in:Blut 1988-08, Vol.57 (2), p.77-83
Main Authors: ANDREESEN, R, SEPHTON, R. G, GADD, S, ATKINS, R. C, DE ABREW, S
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cell Division
Fundamental and applied biological sciences. Psychology
Fundamental immunology
Gallium Radioisotopes
Humans
Immunobiology
Iron Radioisotopes
Macrophages - cytology
Macrophages - metabolism
Macrophages - ultrastructure
Myeloid cells: ontogeny, maturation, markers, receptors
Protein Binding
Receptors, Transferrin - physiology
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Summary:Human blood monocytes (mo) when cultured in suspension on hydrophobic teflon membranes undergo terminal maturation to macrophages (MO). Together with the appearance of new lineage-restricted differentiation antigens, mature MO but not blood mo, express transferrin (TF) receptor molecules as detected by immunostaining methods. Here we report that radio- and fluorescein-labelled TF binds to a single class of high-affinity binding sites on MO but not on mo. As mo mature in vitro in the presence of human serum, their receptor numbers increase to about 10(6) per cell, showing an apparent Kd for Fe2TF of approximately 5 nM. These receptor numbers were comparable with our estimates for cultured K 562 human tumor cells, and about 20x greater than reported for human MO cultured in the presence of fetal calf serum. Our MO showed 58Fe uptake comparable with uptake by tumor cells and also exhibited TF-promoted uptakes of 61Ga. The possibility that MO might recycle stored iron through receptor-bound apoTF was not supported by experiments which showed that their Fe2TF receptors had much lower affinity for apoTF (Kd greater than 1 microM) and which could not detect separate high-affinity receptors specific for apoTF. Expression of TF receptors was not substantially altered by treatment with human recombinant interferon-gamma.
ISSN:0006-5242
1432-0584
DOI:10.1007/BF00319730