Decreased affinity and number of transferrin receptors on erythroblasts in the anemia of rheumatoid arthritis

Abstract

In anemia of chronic disease (ACD) in rheumatoid arthritis (RA) a decreased iron uptake and transferrin binding by erythroblasts are postulated to play a pathophysiological role. To examine whether this is related to changes in transferrin receptor expression by erythroblasts, we studied bone marrow from 5 healthy controls, 5 nonanemic RA patients, and 9 RA patients with ACD. Bone marrow mononuclear cells were incubated with increasing concentrations of ¹²⁵I-transferrin and specific binding data were analyzed by the method of Scatchard. The number of transferrin receptors on erythroblasts from RA patients with ACD was significantly lower as compared to nonanemic RA patients (P < .05) and controls (P < .02). The affinity of the transferrin receptor tended to be lower in ACD. These preliminary data may indicate that transferrin receptor expression by erythroblasts is impaired in ACD. Since the rate of erythroid iron uptake is mainly determined by the number of transferrin binding sites, this may explain a decrease in erythroblast iron availability in ACD in RA.