Synergistic interaction of hematopoietic colony stimulating and growth factors in the regulation of myelopoiesis.

Synergistic interactions in the regulation of myelopoiesis have been noted in vitro and in vivo and are discussed. Moreover, data is presented to highlight such synergistic interactions in vitro and in vivo. It is shown that purified recombinant human B-cell stimulating factor-1/interleukin-4 (rh BSF-1/IL-4) synergizes with rh Granulocyte (G)-Colony Stimulating Factor (CSF), but not with rh Granulocyte-Macrophage (GM)-CSF, rh IL-3, or rh Macrophage CSF (CSF-1) to enhance colony formation in vitro by normal human bone marrow cells. This synergism is restricted to granulocyte progenitors. Also, it is shown that rh G-CSF or rh CSF-1 enhance the proliferation of granulocyte-macrophage progenitor cells (CFU-GM) in vivo in mice pretreated with human lactoferrin, and when added together these preparations of CSF act synergistically. It is apparent that a true understanding of how myeloid blood cell production is regulated requires insight into how molecules collaborate with or antagonise one another.