Lineage switch of a mouse pre-B cell line (SPGM-1) to macrophage-like cells after incubation with phorbol ester and calcium ionophore.

The mouse CD5 positive pre-B cell line SPGM-1 can be induced to switch its lineage commitment towards macrophage differentiation by treatment with a combination of phorbol ester and a calcium ionophore. When cultured with these reagents the pre-B cells ceased to proliferate and rapidly became adherent to plastic surfaces. This morphological change was accompanied by the loss of pre-B cell-specific surface markers, such as PB76 and most prominently the mu heavy chain of the immunoglobulin receptor complex. In addition, the mRNA of the surrogate light chain lambda 5 disappeared while the induction of lysozyme mRNA could be detected. Differentiated SPGM-1 cells phagocytosed latex beads and showed nonspecific esterase activity. The high efficiency and speed of differentiation in this cellular system makes SPGM-1 a highly suitable model for studying the phenomenon of lineage switching during hemopoesis.