Large macrophage colony-forming cells identical to high proliferative potential colony-forming cells in peripheral blood of patients with collagen vascular diseases: High occurrence among patients with systemic sclerosis anddermatomyositis

Objective. To examine peripheral blood (PB) of patients with various collag en vascular diseases (CVD) for the presence of colony-forming cells (CFC) t hat form large macrophage colonies (> 2.5 mm in diameter, > 10,000 cells). Methods. Peripheral blood mononuclear cells were obtained from 92 patients with various active CVD and 20 healthy controls, and assayed for in vitro c olony formation. There were 14 patients with systemic lupus erythematosus ( SLE), 30 with rheumatoid arthritis (RA), 17 with systemic sclerosis (SSc), 20 with polymyositis (PM)/dermatomyositis (DM) (11 PM, 9 DM) and 11 with sy stemic vasculitis. Results. Large macrophage CFC were detected in PB of 7% of patients with SL E (1/14), 17% with RA (5/30), 47% with SSc (8/17), 30% with PM/DM (6/20) [9 % PM (1/11) and 56% DM (5/9)], 0% of those with systemic vasculitis (0/11) and 0% of the healthy subjects (0/20). There was a significant difference b etween the occurrence of CFC in patients with PM versus patients with DM (p < 0.05). The occurrence of CFC in patients with SSc or DM was significantl y higher than that in patients with other CVD including SLE, RA, PM, and sy stemic vasculitis (p < 0.05). Conclusion. Based on the size of the colonies they formed, the CFC correspo nded to high proliferative potential colony-forming cells, a subset of prim itive hematopoietic cells. Our findings among patients with CVD indicate th at these primitive hematopoietic progenitor cells, which are believed to co nstitute a noncirculating population in healthy individuals, are found most frequently in PB of patients with SSc and DM. It is likely that primitive hematopoietic cells are frequently mobilized into the peripheral circulatio n during the pathogenesis of SSc and DM.