To examine peripheral blood (PB) of patients with various collagen vascular diseases (CVD) for the presence of colony-forming cells (CFC) that form large macrophage colonies (> 2.5 mm in diameter, > 10,000 cells).
Peripheral blood mononuclear cells were obtained from 92 patients with various active CVD and 20 healthy controls, and assayed for in vitro colony 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 systemic vasculitis.
Large macrophage CFC were detected in PB of 7% of patients with SLE (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 between 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 significantly higher than that in patients with other CVD including SLE, RA, PM, and systemic vasculitis (p < 0.05).
Based on the size of the colonies they formed, the CFC corresponded to high proliferative potential colony-forming cells, a subset of primitive hematopoietic cells. Our findings among patients with CVD indicate that these primitive hematopoietic progenitor cells, which are believed to constitute 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 circulation during the pathogenesis of SSc and DM.