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An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization
Published on: June 12, 2013
Immunological properties of ferritin during in vitro maturation of human monocytes
1Department of Haematology, University of Wales College of Medicine, Cardiff, U.K.
Insights
Monocyte maturation in vitro leads to a decrease in H-rich ferritin and an increase in L-rich ferritin, especially after iron exposure. This study models ferritin synthesis changes during monocyte development.
Area of Science:
- Cellular Biology
- Immunology
- Biochemistry
Background:
- Tissue macrophages, derived from peripheral blood monocytes, exhibit ferritin rich in L subunits.
- Peripheral blood monocytes initially contain a higher proportion of H subunits in their ferritin.
Purpose of the Study:
- To investigate the in vitro maturation of monocytes and changes in cellular ferritin composition.
- To examine the immunological properties of ferritin during monocyte differentiation.
Main Methods:
- Isolation of mononuclear cells and monocytes from healthy individuals and idiopathic haemochromatosis patients.
- In vitro incubation of monocytes with and without iron (ferric ammonium citrate) for varying durations (20 hours and 7 days).
- Quantification of H- and L-rich isoferritins using specific immunoassays.
Main Results:
- Freshly isolated monocytes showed similar concentrations of H- and L-rich isoferritins.
- Iron incubation increased both H- and L-type ferritins in monocytes.
- After 7 days of maturation, monocytes predominantly contained L-rich ferritin, with iron promoting L-type accumulation but not H-type.
Conclusions:
- Monocyte maturation in vitro is associated with a reduction in H-rich isoferritins.
- Iron supplementation during maturation enhances L-type ferritin accumulation.
- In vitro monocyte maturation serves as a valuable model for studying ferritin synthesis and degradation control.
Abstract:
Ferritin in macrophages from human liver and spleen is rich in L subunits but, in the peripheral blood monocytes from which tissue macrophages are derived, the ferritin contains a high proportion of H subunits. We have studied the maturation of monocytes in vitro and the immunological properties of cellular ferritin during this process. Mononuclear cells were isolated from peripheral blood of normal subjects and patients with idiopathic haemochromatosis. Monocytes were obtained by incubation on plastic. The adherent cells were incubated in medium with or without added iron (ferric ammonium citrate) for 20 hours and harvested. Monocytes were also incubated for 7 days before incubation with iron. Ferritin concentrations were determined using immunoassays specific for H and L rich isoferritins. Freshly isolated monocytes were found to have similar concentrations of H- and L-rich isoferritins. Incubation with iron caused an increase in both H- and L-type ferritins. After incubation for 7 d the ferritin present in the normal cell lysates was L-rich and incubation with iron caused accumulation of L-, but not H-type ferritin. Maturation of monocytes is thus associated with the loss of H-rich isoferritins. There were no differences between normal subjects and patients with idiopathic haemochromatosis in ferritin concentrations. In vitro maturation provides an excellent model for studying the developmental control of ferritin synthesis and breakdown.
