In Vitro Modulation of Human Erythropoiesis by Lymphocyte-Rich Fractions of Blood

It is generally accepted that erythropoiesis in mammals is regulated primarily by the hormone erythropoietin (Ep).1,2 Several lines of evidence suggest that cell-cell interactions also play an important role in the production of erythrocytes. Trentin,3 for example, described an erythroid hematopoietic inductive microenvironment (HIM) that plays an important role in directing the differentiation of the multipotential stem cell or its progeny toward the erythroid line. A defect in the HIM is considered to be responsible for the genetically determined anemia seen in Steel mice.4 Cells responsible for the HIM are thought to be a type of reticuloendothelial cell, since they exhibit resistance to ionizing irradiation.