BIOLOGICAL AND BIOCHEMICAL-PROPERTIES OF A SERUM FACTOR THAT STIMULATES SPLENIC HEMATOPOIESIS IN MICE

Abstract

Some biological and biochemical properties of a distinct hemopoietic factor that stimulates splenic hemopoiesis in mice are described. This factor can be detected by measuring the increase in the number of in vitro hemopoietic colony-forming cells (CFCs) in the spleens of mice after transfer of serum from syngeneic donors that have been treated previously with the bacterial cell-wall components: lipid A or lipoprotein. Serum collected 5 min after the IV injection of lipid A contained almost no splenic hemopoiesis-stimulating factor (SHSF). The highest serum levels of the factor were found between 30 min and 3 h after lipid A was injected IV. The residual levels of lipid A or lipoprotein in t..