EPO and rheumatoid arthritis: A role for erythropoietin-producing human hepatocellular receptors (ephrin receptors) in the aetiology of systemic inflammatory diseases such as RAhas previously been postulated34; although evidence to support this speculation has been lacking, high levels of ephrin B1 ligand were reported in peripheral and synovial T lymphocytes (T cells) in a small study with RA patients35.