Abstract
There are different types of hematopoietic regulatory proteins that regulate the multiplication and differentiation of normal myeloid cells. These different types include four growth-inducing proteins called colony-stimulating factors (CSF), including interleukin-3 (IL- 3), or macrophage and granulocyte inducers, type 1 (MGI-1); another type (called MGI-2) that induces myeloid differentiation of normal myeloid cells without inducing myeloid cell multiplication; and interleukin-1 (IL-1), which can act on myeloid precursor cells. Different clones of myeloid leukemic cells can differ in their ability to be induced to undergo terminal cell differentiation by different hematopoietic regulatory proteins. We have now studied the ability of cyclosporine A and recombinant IL-1 alpha to regulate in vivo differentiation of different clones of myeloid leukemic cells that are either susceptible or resistant to induction of differentiation by IL-1 in vitro. The results show that (a) cyclosporine A, like other immune- suppressing compounds such as cyclophosphamide, inhibited in vivo differentiation of myeloid leukemic cells and differentiation was restored by injecting recombinant GM-CSF; (b) recombinant IL-1 alpha induced in vivo terminal differentiation of IL-1-sensitive but not IL-1- resistant clones of myeloid leukemic cells; (c) IL-1 alpha and GM-CSF synergistically induced differentiation in vivo in a GM-CSF-responsive and IL-1-nonresponsive clone of leukemic cells; and (d) IL-1 alpha induced in vivo the rapid production and release into serum of the differentiation-inducing protein MGI-2 as well as the growth-inducing proteins M-CSF and G-CSF.
