In Vitro Effect of Neopterin on Erythropoiesis in Mice

Neopterin is produced by monocytes and a useful biomarker of inflammatory responses. We found recently in mice that neopterin suppressed erythropoiesis but enhanced myelopoiesis possibly by activating stromal cells, the same phenomenon observed in inflammation. In this study, we investigated whether neopterin affects the proliferation and differentiation of immature erythroid progenitor cells (BFU-E) by stimulating bone-marrow stromal cells in culture. Neopterin decreased the number of colonies of BFU-E formed by unfractionated bone-marrow cells in a semisolid culture system, but increased the number of granulocyte-macrophage progenitor cells (CFUGM). In contrast, it did not affect numbers of BFU-E or CFU-GM among a lineage-negative (fractionated) bonemarrow- cell population cultured without stromal cells. These results suggest that neopterin decreased the number of colonies of BFU-E by activating bone-marrow stromal-cell function.