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Phenotypic characterization of gamma interferon-induced human monocyte polykaryons
Abstract:
Multinucleated giant cells of mononuclear phagocyte origin (monocyte or macrophage polykaryons [MPs] ) are seen in numerous different normal and pathologic states. We have previously shown that gamma interferon (IFN-gamma) induces fusion of uninuclear monocytes (UMs) to form MPs. This study was designed to characterize these IFN-gamma-induced MPs. Control and IFN-gamma-treated UMs and MPs did not have peroxidase activity, but they stained intensely for nonspecific esterase and acid phosphatase. The esterase of UMs and MPs was abolished by fluoride, but the acid phosphatase of UMs and MPs was only minimally decreased by tartrate. The phagocytosis of polystyrene spheres and glutaraldehyde-fixed erythrocytes by MPs was moderately depressed as compared with control or treated UMs, whereas the phagocytosis of IgG-coated erythrocytes was markedly depressed. Populations of control monocytes produced less H2O2 in response to 200 nmol/L of phorbol myristate acetate than did IFN-gamma-treated monocytes (37 +/- 7 v 199 +/- 29 nmol/h per milligram of cell protein). However, when examined microscopically, individual MPs had less ability to reduce NBT (18% +/- 5% positive for MP, 91% +/- 3% for treated UMs, and 67% +/- 3% for control UMs). The surface membrane antigens Leu M3, OKM1 (C3bi receptor), DU-HL60-3, DU-HL60-4, TE5, and V1 were not expressed or were expressed poorly in MPs; they were expressed normally in control and treated UMs. However, HLA-DR expression was increased in treated UMs and MPs. The binding of the lectins RCA, Con A, WGA, DBA, UEA, and PNA was equivalent in all cells. Thus, MPs formed by fusion of UMs in vitro after culture with IFN-gamma differ in several features from UMs.
Insights
Gamma interferon (IFN-gamma) induces fusion of monocytes into multinucleated giant cells (macrophage polykaryons [MPs]). These IFN-gamma-induced MPs exhibit distinct characteristics compared to uninuclear monocytes (UMs), impacting phagocytosis and cell surface antigen expression.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Multinucleated giant cells, termed macrophage polykaryons (MPs), originate from mononuclear phagocytes like monocytes or macrophages.
- These MPs are observed in various physiological and pathological conditions.
- Previous research demonstrated that gamma interferon (IFN-gamma) promotes the fusion of uninuclear monocytes (UMs) to form MPs.
Purpose of the Study:
- To thoroughly characterize the features of macrophage polykaryons (MPs) induced by IFN-gamma.
- To compare the functional and phenotypic properties of IFN-gamma-induced MPs with uninuclear monocytes (UMs).
Main Methods:
- Enzyme activity assays (peroxidase, non-specific esterase, acid phosphatase) were performed on UMs and MPs.
- Phagocytosis assays using polystyrene spheres and erythrocytes (coated and uncoated) were conducted.
- Hydrogen peroxide (H2O2) production and nitroblue tetrazolium (NBT) reduction were measured.
- Flow cytometry was used to analyze the expression of surface membrane antigens and HLA-DR.
- Lectins were employed to assess cell surface binding characteristics.
Main Results:
- IFN-gamma-induced MPs showed depressed phagocytosis of spheres and fixed erythrocytes, and markedly depressed phagocytosis of IgG-coated erythrocytes compared to UMs.
- MPs exhibited reduced H2O2 production and NBT reduction compared to UMs.
- Key surface antigens (Leu M3, OKM1, etc.) were absent or poorly expressed on MPs, while HLA-DR expression was increased.
- Enzyme profiles indicated intense non-specific esterase and acid phosphatase activity, unaffected by tartrate but abolished by fluoride for esterase.
Conclusions:
- Macrophage polykaryons formed by IFN-gamma-induced monocyte fusion in vitro possess distinct biochemical and functional characteristics compared to uninuclear monocytes.
- These differences include altered phagocytic capacity, reduced oxidative burst potential, and differential expression of surface markers.
- The findings highlight the significant cellular changes occurring during monocyte-macrophage differentiation and fusion induced by IFN-gamma.