The present invention provides novel use of the MK family that is used alone
as an agent for proliferating hematopoietic stem cells and hematopoietic precursor
cells. The invention also provides an agent for remarkably enhancing the above-described
effect for promoting the proliferation of hematopoietic stem cells and hematopoietic
precursor cells, comprising the MK family in combination with known hematopoietic
factors such as IL-3, IL-6, G-CSF, GM-CSF, M-CSF, SCF, and EPO.