Stimulation of human hematopoietic colony formation by recombinant gibbon multi-colony-stimulating factor or interleukin 3.

Recently, the gene for a novel mammalian hematopoietic growth factor homologous to murine interleukin 3 was isolated from a gibbon T cell line and expressed in monkey COS cells. The factor, termed multi-colony stimulating factor (multi-CSF) or interleukin 3, is stimulatory to human target cells. We investigated the range of enriched human bone marrow and fetal liver hematopoietic progenitors responsive to multi-CSF; compared the colony types observed with those obtained in the presence of recombinant granulocyte-macrophage CSF (GM-CSF); and analyzed the effects on colony formation of combining multi-CSF with GM-CSF or granulocyte-CSF (G-CSF). The results show that multi-CSF acts as a multipoietin. Alone it stimulates the formation of colonies derived from granulocyte, macrophage, eosinophil, and megakaryocyte progenitors. In combination with erythropoietin it supports the development of both erythroid and mixed colonies. Furthermore, the data show that multi-CSF is a more potent stimulus of erythroid progenitors than GM-CSF. In combination with G-CSF multi-CSF substantially increases granulocyte colony number over the number obtained with each factor alone. We conclude that multi-CSF may prove to have important therapeutic potential in vivo as a stimulus for hematopoiesis.

Combinations of recombinant colony-stimulating factors are required for optimal hematopoietic differentiation in serum-deprived culture.

Previous in vitro investigations on enriched human hematopoietic progenitors have led to the conclusion that the purified recombinant multipoietins, interleukin 3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) can alone induce the formation of colonies from a variety of multipotent and lineage committed progenitors. Since fetal calf serum was included in these cultures and itself might contain growth factors or other cofactors, we re-examined the actions of the CSFs in serum-deprived conditions. Results show that both the multipoietins are inadequate stimuli of colony formation. At maximal concentrations IL-3 alone induces only 25% of the granulocyte and macrophage colony-forming units (CFU-G and CFU-M) produced by a T-cell conditioned medium that contains a mixture of CSFs. When IL-3 was added at the initiation of the cultures and erythropoietin (ep), G-CSF, or M-CSF added on day 3, almost full recovery of erythroid, granulocytic, and monocytic colonies, respectively, was obtained. Similar results were obtained with GM-CSF except that fewer erythroid colonies were recovered at high concentrations, and almost maximal CFU-M proliferation could be induced. These results show that in serum-deprived conditions, the multipoietins must be combined with lineage specific CSFs for full progenitor expression.