Human macrophage hybrid forming spontaneous giant cells

Thymidine kinase-deficient clones of the human monocyte/macrophage cell line U-937 were established and used for fusion experiments with separated normal human blood monocytes. A hybrid (H 29) was generated during HAT-selection procedure, about 50% of which formed spontaneous giant cells, as shown by morphological, immunocytochemical, and chromosomal analyses. It is concluded that giant cells originate from monocytes and display mitotic activity. Macrophage hybrids are the basic requirement for the elucidation of monocyte/macrophage heterogeneity and immortalization of their functional properties.