['Erythropoietin (Epo) was originally defined as a hematopoietic growth factor, but also has potent tissue-protective properties. The cytokine-modulating actions of Epo have received scant attention. We hypothesized that Epo significantly influences the in vitro cytokine production in both neonates and adults.', 'The effects of Epo were investigated using a standardized in vitro whole blood assay. Production of various cytokines was assessed by means of intracellular cytokine detection (IL-2, -6, -8, IFN-gamma and TNF-alpha) in preterm infants, term neonates and adults. Furthermore, synthesis of IL-4, -5 and -10 in adults was investigated via cytometric bead array.', 'Epo significantly inhibits the production of various cytokines in preterm infants, term neonates and adults. In CD3+ lymphocytes, Epo predominantly decreases the number of IL-2-positive cells in all age groups. Similarly, in CD14+ cells, Epo significantly diminishes the number of IL-6- and TNF-alpha-producing cells. Furthermore, Epo significantly inhibits the synthesis of IL-4, IL-5 and IL-10 in adults.'] Does erythropoietin inhibit cytokine production of neonatal and adult leukocytes?