Left, steady state erythropoiesis is increased by increased levels of erythropoietin (Epo). Right, Inflammation compromises steady state erythropoiesis, which leads to activation of the BMP4 dependent stress erythropoiesis pathway. MPP-multipotential progenitors, CMP- common myeloid progenitor, MEP-megakaryocyte erythroid progenitor, GMP- granulocyte macrophage progenitor, BFU-e- burst-forming units- erythroid, CFU-E- colony forming units-erythroid. The megakaryocyte pathway is not shown in order to simplify the diagram.