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Paramagnetic microspheres as immunological markers for light and electron microscopy
M T Rana1, E C Pearson, C R Barker
1Department of Haematological Medicine, University of Cambridge Clinical School, U.K.
Abstract:
M-450 Dynabeads are magnetizable polystyrene microspheres 4.5 micron in diameter to which antibodies of IgM isotype can be physically adsorbed. Antibody-coated Dynabeads can be used to label cell surfaces and then to separate the rosetted cells by application of an external magnetic field. We demonstrate here, using cell lines K562 and U937 and the previously undescribed monoclonal antibodies CH-F42 and CH-E25, that Dynabeads can also be used to label cells at the ultrastructural level. Dynabeads can therefore provide a useful bridge between light and electron microscopy. The preservation of specific rosettes at the ultrastructural level without the formation of artifactual aggregates requires rapid but gentle fixation in dilute suspension. We have achieved this by fixing briefly in a large volume of buffered glutaraldehyde followed by neutralization of excess glutaraldehyde with ethanolamine.
Insights
Magnetizable microspheres (Dynabeads) can label cell surfaces for separation. This study shows Dynabeads can also label cells for ultrastructural analysis, bridging light and electron microscopy.
Area of Science:
- Cell biology
- Microscopy techniques
- Immunotechnology
Background:
- M-450 Dynabeads are magnetizable polystyrene microspheres used for cell surface labeling and separation.
- Antibodies of the IgM isotype can be adsorbed onto Dynabeads for specific cell targeting.
- Current applications primarily involve light microscopy and cell separation via magnetic fields.
Purpose of the Study:
- To investigate the utility of Dynabeads for ultrastructural cell labeling.
- To demonstrate Dynabeads as a tool bridging light and electron microscopy.
- To establish optimal fixation methods for preserving Dynabead-labeled cells at the ultrastructural level.
Main Methods:
- Utilized M-450 Dynabeads coated with novel monoclonal antibodies (CH-F42, CH-E25).
- Applied Dynabeads to label cell lines K562 and U937.
- Developed a rapid, gentle fixation protocol using buffered glutaraldehyde and ethanolamine for ultrastructural preservation.
Main Results:
- Successfully demonstrated ultrastructural labeling of cells using antibody-coated Dynabeads.
- Observed preservation of specific rosettes without artifactual aggregates.
- Validated the method on K562 and U937 cell lines.
Conclusions:
- Dynabeads can be effectively used for ultrastructural cell labeling, extending their application beyond light microscopy.
- The developed fixation technique preserves cellular integrity and specific labeling for electron microscopy.
- Dynabeads offer a valuable tool for correlative light and electron microscopy studies.