A factor inducing differentiation of mouse myeloid leukemia cells in human amniotic fluid.

: The M1 line cells of mouse myeloid leukemia can be induced to differentiate in vitro into macrophages by a factor in human amniotic fluid. The macrophages showed phagocytosis and locomotic activity, and also gained Fc receptors on the cell surface. This factor in amniotic fluid capable of inducing differentiation of M1 cells was heat-labile, trypsin-sensitive, and non-dialysable. A growth-stimulating factor for the M1 cells was also found in the human amniotic fluid, and it was heat-stable and trypsin-resistant. The conditioned medium obtained from the amnion had the activity of differentiating the M1 cells.