[Regulation of the proliferation of granulocyte-macrophage progenitors in human bone marrow]

The colony stimulating activity (CSA) of bone marrow cells in 50 children with normal bone marrow was studied. A method for quantitative estimation of CSA of bone marrow cells has been suggested. Essential distinctions between CSA of bone marrow cells and that of peripheral blood leukocytes were established considerable decrease mainly at the expense of reduction of the proliferation of colony-forming progenitors was found. CSA of bone marrow cells appears to be a result of complicated interaction between bone marrow adherent and non-adherent fractions. Each of these two fractions produces approximately the similar level of CSA which is lower than that of unfractionated bone marrow. It is supposed that there are two types of granulocyte macrophage progenitors in the human bone marrow which are specifically-sensitive to CSA of leukocytes and bone marrow cells and possess different proliferative potential.