Induction of multinucleated giant cells from rheumatoid arthritis (RA) synovial adherent cells by anti-DR antibody.

To determine the effects of signalling through the DR molecule on synoviocytes from RA patients, the synovial adherent cells were incubated with anti-DR antibodies. After 24 h incubation, we found the formation of multinucleated giant cells in that culture. These multinucleated giant cells showed characteristics of monocyte-macrophage lineage cells and precursor of osteoclasts. Cyclohexamide inhibited the formation of multinucleated giant cells, but not the aggregation of synovial cells, suggesting that newly synthesized proteins are associated with the cell fusion. These results revealed a new mechanism in multinucleated giant cell formation.