The Effect of Neutropenia on Myeloid Growth and the Stem Cell in an In Vivo Culture System

An in vivo diffusion chamber (DC) culture technique was used to evaluate the role of circulating humoral factors in the control of myelopoiesis. Normal mouse bone marrow cell suspensions sealed in DC’s were implanted intraperitoneally into mice or rats rendered neutropenic by pretreatment with cyclophosphamide, and the growth of cells in the DC’s was evaluated at intervals thereafter. When marrow was cultured in hosts with graded neutropenia, a dose-related augmentation of myelopoiesis was demonstrated. The growth of macrophages and of pluripotent stem cells, measured by the spleen colony-forming technique, was also enhanced by culture in neutropenic hosts. These data provide further evidence that the rate of myelopoiesis is influenced by a circulating humoral factor. They further suggest that a humoral or hormonal factor is important in control of the pluripotent stem cell population.