The EPO-induced increase in spleen size was clearly dependent on iron availability, as the spleens from EPO-treated mice kept on low-iron diet were significantly smaller than spleens from EPO-treated mice kept on control diet (Fig 5E); nevertheless, the EPO-induced increase in splenic Fam132b mRNA and Tfr2 mRNA content was not influenced by iron deficiency (Fig 5F and Fig 4F). This evidence concerns the gene ERFE and nutritional disorder.