[A Novel Inhibitory Factor of Erythropoietin: Anti-Erythropoietin Receptor Antibody and Its Characteristics].

During the exploration of factors that interfere with the erythropoietin (EPO) -EPO receptor (EPOR) interaction in anemia, a novel inhibitory factor of EPO, anti-EPOR antibody, has been detected in anemic pa- tients with immune-mediated diseases. The study also demonstrated that the antibodies were observed in some patients with chronic kidney disease (CKD). EPOR is known to be expressed not only in bone mar- row erythroblasts, but also in other organs including the kidneys. In addition, previous studies showed that EPO may contribute to protecting the kidneys from injury by binding EPOR on renal resident cells as well as through the correction of anemia. Based on this background, we recently examined the clinical significance of anti-EPOR antibodies in patients with CKD. With regard to patients with lupus nephritis, who showed the highest antibody levels among the patients examined, the antibodies were associated with overall disease activity and cell infiltration in the injured kidney, and they were inversely related to the preserved renal function. Here, we discuss the discovery of anti-EPOR antibodies in patients with anemia and CKD, and the possibil- ity of their use as an additional biomarker for the deterioration of the renal function. [Review].