Proliferation of single hemopoietic progenitor cells in the absence of colony-stimulating factors and serum.

The proliferative capacity of partially purified populations of mouse bone marrow progenitor cells has been examined in serum-free cultures in the presence and absence of colony-stimulating factors (CSFs). The half-life of progenitor cells was approximately 25 h in the absence of factor, regardless of whether the factor used to rescue the cells was granulocyte-macrophage CSF (GM-CSF), granulocyte CSF (G-CSF), or interleukin 3 (Il-3). During 4 days of culture without stimulator, the cells proliferated with a doubling time of about 24 h, in contrast to 8-12 h in response to exogenous CSF. To determine if this apparent CSF-independent proliferation was due to production of factors in situ, colony and single-cell transfer experiments were performed in serum-free media. The results showed that isolated hemopoietic progenitor cells can respond to GM-CSF, G-CSF, or Il-3 to give clones of greater than 100 mature granulocytes and macrophages after 4 days. Some transferred cells divided up to four times in the absence of factor, giving rise primarily to neutrophils. Even after an acidic wash, single cells were able to divide up to three times without stimulator, indicating that surface-bound factor can account for at most one division.