Anaemia in rheumatoid arthritis (RA) is a common and debilitating complication. The most common causes of this anaemia are iron deficiency and anaemia of chronic disease. Investigations have suggested that interleukin 1 (IL-1) or tumour necrosis factor (TNF), or both, from monocytes associated with chronic inflammation are responsible for the anaemia of chronic disease. On bone marrow examination anaemia of chronic disease is characterised by the diversion of iron from the erythropoietic compartment into marrow macrophages. This phenomenon is termed failure of iron utilisation. In this study, CFU-E (colony forming unit erythroid; late red cell precursors) and BFU-E (burst forming unit erythroid; early red cell precursors) stem cells were cultured from 10 normal marrow samples and 12 marrow samples from patients with RA with iron deficiency anaemia and 10 samples from patients with RA with failure of iron utilisation. All patients with RA were anaemic (haemoglobin less than 100 g/l), Potential accessory or inhibitory cells of erythropoiesis (CD4, CD8, or CD14 positive cells) were removed before culture. Control marrow samples were studied in a similar manner. Normal marrow samples yielded 377 (17) CFU-E and 133 (6) BFU-E (mean (SD)) colonies for each 2 x 10(5) light density cells plated. CD4 ablation caused reductions of 62 and 100% in CFU-E and BFU-E colonies respectively. CD14 removal resulted in considerable but lesser reductions of 46% for CFU-E and 25% for BFU-E. In both groups of patients with RA, CFU-E colony numbers were significantly lower than those seen in normal control subjects, 293 (17) for patients with iron deficiency anaemia and 242 (35) for patients with failure of iron utilisation. BFU-E colony numbers were 102 (13) and 108 (20) respectively. In patients with RA, CD4 removal caused a significantly greater loss of CFU-E colonies compared with normal control subjects. Cytolysis of CD14 positive cells caused a reduction in CFU-E colonies in the two RA groups which was similar to that seen in normal subjects. In conclusion, patients with RA seem to have fewer CFU-E progenitors but essentially normal numbers of BFU-E stem cells. Our data suggest a stimulatory role for marrow CD4 and CD14 cells in erythropoiesis in patients with RA. Monocytes-macrophages (CD14 positive) are known to be producers of IL-1 or TNF, or both, however, the predicted increase in the CFU-E colonies on removal of CD14 cells is not seen. Therefore, if IL-1 or TNF, or both, are responsible for the impairment of erythropoiesis in patients with RA, marrow macrophages are unlikely to be the source. Moreover, these results indicate the probability of erythropoietin resistance on the basis of diminished CFU-E colony formation in patients with RA.
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