Abstract: | Molecules of low molecular weight, able to stimulate colony formation by human granulopoietic cells, were prepared from media conditioned by normal and leukemic human peripheral blood leukocytes. When molecules from these sources were studied, heterogeneity was observed in their ability, after radioiodination, to bind and suicide granulopoietic progenitors, in their radiolabelled tryptic digestion products and in their biological activity as stimulators of granulocyte colonies. |