The role of interleukin 1, erythropoietin and red cell bound immunoglobulins in the anaemia of rheumatoid arthritis.
Since interleukin 1 (IL-1) and erythropoietin (Epo) are believed to play a role in the pathogenesis of rheumatoid arthritis (RA) anaemia we measured IL-1 alpha and Epo concentrations in 10 RA patients with chronic disease anaemia (CDA) and in 14 RA patients without anaemia. Anaemic RA patients had significantly higher IL-1 alpha concentrations than patients without anaemia. IL-1 alpha correlated negatively with haemoglobin and correlated positively with ESR. The results of a multivariate analysis showed that the best predictors of the presence and absence of anaemia were IL-1 alpha and ESR. No clinical parameters permitted a distinction between these two groups of patients. Epo levels were not different in anaemic and non-anaemic RA patients. No correlation was found between Hb and Epo, indicating the presence of an impaired Epo response in RA patients with CDA. We completed our study with the determination of the mean red cell lifespan and with the quantification of IgG and IgM bound to the surfaces of red blood cells (RBC-IgG and RBC-IgM) using a sensitive ELISA method. We observed a modest reduction in red cell survival in anaemic RA patients compared to normal controls. We did not find any correlation between Hb and red cell lifespan and between Hb and RBC-IgG. RBC-IgG and RBC-IgM were not found to be more elevated in anaemic RA than in non-anaemic patients.