Human pluripotent colony stimulating factor (Pluripoietin) was shown to act synergistically with human pluripotent alpha-like colony-stimulating activity (Pluripoietin-alpha) supporting the proliferation and differentiation of human CFU-GM progenitor cells in vitro, increasing colony size and numbers. In addition, Pluripoietin enhanced cytotoxic activity of mature human neutrophil granulocytes in an antibody-dependent cellular cytotoxicity assay. Biological activities of Pluripoietin known so far suggest great potentials for clinical use. Preclinical in vivo studies of Pluripoietin in different disease situations may be feasible in mice, because Pluripoietin is active on granulocyte precursors and on a variety of other murine cells.