Syncytium formation in aged umbilical cord blood macrophages. Attempts to demonstrate an infectious etiology
Related Experiment Video
Updated: Sep 11, 2026
Isolation of Precursor B-cell Subsets from Umbilical Cord Blood
Published on: April 16, 2013
Abstract:
About 50% of cultures of mononuclear cells from human umbilical cord blood kept for more than 6 weeks in tissue culture reveal syncytium formation of adherent cells involving varying percentages of cells. Syncytium formation usually occurs focally producing plaques of multinucleated giant cells followed by cell degeneration. Occasionally, plaques of giant cell formation of adherent cells were also noted in macrophage cultures obtained from healthy adult blood donors. Attempts to transfer cytopathogenic changes to other human epithelial and fibroblastic cells in tissue culture were unsuccessful. In three instances, however, fibroblast-like cells started to grow spontaneously in umbilical cord blood cultures revealing syncytium formation and were subcultured once or twice. Six to eight weeks after their appearance, these cells too degenerated spontaneously also showing syncytium formation. Nuclei of the fused cells contained prominent nucleolus-like structures. Electron microscopy failed to demonstrate viral particles within these intranuclear inclusions. Occasionally, however, virus-like particles resembling in size and some structural features that of herpesviruses, were found in degenerating cells. Nucleic acid hybridizations performed with cellular DNA derived from such cultures and 32P-labelled DNA of herpesvirus saimiri and human cytomegalovirus failed to reveal any homologies. In a series of human sera tested for reactivity against fused cells in an indirect immuno-fluorescence test, two reacted specifically at low titer against the nucleolus-like structures of syncytial cells and some additional mononuclear cells.
Insights
Syncytium formation, characterized by multinucleated giant cells, was observed in human umbilical cord blood cultures. These findings suggest potential cellular changes in long-term cultures, with some virus-like particles noted.
Area of Science:
- Cell Biology
- Virology
- Immunology
Background:
- Mononuclear cells from human umbilical cord blood cultured long-term can exhibit syncytium formation.
- This phenomenon involves the development of multinucleated giant cells and subsequent cell degeneration.
- Similar changes were occasionally observed in adult macrophage cultures.
Purpose of the Study:
- To investigate the nature and potential cause of syncytium formation in human umbilical cord blood cultures.
- To determine if the observed cytopathogenic changes are transferable to other cell types.
- To explore the presence of viral agents or specific immune responses associated with syncytium formation.
Main Methods:
- Long-term tissue culture of mononuclear cells from human umbilical cord blood and adult donors.
- Light microscopy for observing syncytium and giant cell formation.
- Attempts at cell transfer to assess cytopathogenicity.
- Electron microscopy to identify potential viral particles.
- Nucleic acid hybridization to detect homology with known herpesviruses.
- Indirect immunofluorescence tests using human sera.
Main Results:
- Syncytium formation occurred in approximately 50% of long-term umbilical cord blood cultures, leading to cell degeneration.
- Spontaneously growing fibroblast-like cells in some cultures also showed syncytium formation and degeneration.
- No successful transfer of cytopathogenic changes to other cell types was achieved.
- Electron microscopy revealed occasional virus-like particles resembling herpesviruses, but nucleic acid hybridization showed no homology with tested herpesviruses.
- Two human sera showed low-titer reactivity against syncytial cell structures in immunofluorescence tests.
Conclusions:
- Long-term culture of human mononuclear cells can lead to spontaneous syncytium formation and degeneration.
- The observed phenomenon is not readily transferable and lacks clear association with known herpesviruses based on hybridization.
- The presence of nucleolus-like structures and limited serum reactivity suggests a potential, yet unidentified, cellular or infectious process.
