Abstract: The invention derives from the discovery of cells, non-adherent (NA) cells, which have properties indicating that they may be pluripotent lymphohematopoietic progenitor cells. These cells, and the stromal cells derived from bone marrow cultures, produce factors which stimulate the growth of primitive cell colonies, as reflected in their stimulation of the growth of colonies of NA cells. These primitive cell colony stimulating factors (PC-CSFs) may be useful in the treatment of disorders which can be alleviated by the proliferation of desired cells. In addition, the NA cells and/or PC-CSF(s) may provide an alternative and/or supplementary method to bone marrow transplantation to alleviate hematopoietic disorders.