PHENOTYPIC CHARACTERISTICS OF BONE-MARROW CELLS IN PATIENTS WITH RHEUMATOID-ARTHRITIS

Objective. Our previous study showed the presence of abnormal myeloid lineage cells in the epiphyseal bone marrow adjacent to joints affecte d with severe rheumatoid arthritis (RA). Now, we investigated whether there were any changes of other marrow cell populations related to RA, and whether there were any pathologically characteristic changes in t he iliac bane marrow, which is one of the major systemic hematopoietic organs. Methods. 2-Color flow cytometry was carried out to analyze th e phenotypes of mononuclear cells (MNC) fractions in bone marrow aspir ates and venous blood from 56 patients with RA and 7 non-RA controls. Results. The absolute number of MNC in the iliac bone marrow was incre ased by 3-fold in the RA patients compared with the non-RA controls. I n contrast, no significant increase of MNC was observed in the tibial epiphyseal bone marrow or peripheral blood. The ratio of each MNC frac tion in the iliac bone marrow did not differ significantly between the RA patients and the non-RA controls. In lymphocyte subsets, the perce ntage of HLA-DR+CD8+ cells to all CD8 cells in the iliac bone marrow i ncreased significantly in the RA patients compared with the non-RA con trols. Abnormal myeloid cells (MX-GA+MY4+ cells), specific to severe R A, were found to be more concentrated in the iliac bone marrow than in the tibial epiphyseal bone marrow. Conclusion. Characteristic patholo gic changes of the iliac bone marrow suggest an important role of syst emic bone marrow in the progression of RA.