Increased myeloid colony growth in vitro of precultured progenitor cells

Human peripheral blood myeloid progenitor cells (GM-CFU) form markedly more colonies in soft agar following a short-term preculture in vitro. This enhancement is independent of monocytes and T lymphocytes and reflects an alteration of progenitor cells themselves. The preculture increases the number of cells being in the S phase of cell cycle and renders them relatively independent of exogenous CSF.