Serum and bone marrow from 21 patients with rheumatoid arthritis (RA) were studied in order to establish the pathogenetic role of interleukin-6 (IL-6) in anemia of chronic disease (ACD). Erythroid colony growth, using burst forming units of erythroblasts (BFUe) as a parameter, was impaired in ACD and not in nonanemic RA controls. Serum IL-6 was elevated in ACD and it correlated well with parameters of disease activity such as erythrocyte sedimentation rate and C-reactive protein. IL-6 addition to bone marrow cultures had inconsistent effects while anti-IL-6 addition resulted in impaired erythroid colony growth, suggesting stimulatory effects of IL-6 produced in the medium, which may be masked by simultaneous production of cytokines with suppressive effects. It was concluded that elevated serum IL-6 in ACD reflects disease activity. It probably plays no pathogenetic role in ACD. Its stimulatory effects on erythroid growth might counteract suppressive effects of other interleukins.

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Rheumatology International
Department of Clinical Chemistry

Vreugdenhil, G, Löwenberg, B, van Eijk, H.G, & Swaak, A.J.G. (1990). Anaemia of chronic disease in rheumatoid arthritis - Raised serum interleukin-6 (IL-6) levels and effects of IL-6 and anti-IL-6 on in vitro erythropoiesis. Rheumatology International, 10(3), 127–130. doi:10.1007/BF02274827