Does stem cell self renewal and progenitor cell commitment operate through an effector-memory cell mechanism?
We propose a model for stem cell self renewal and transition into commitment towards a variety of cell lineages. In this model the production of both “effector cells” (as represented by the mature cells in the different cell lineages) and of progenitor “memory” lymphocytes, takes place concomitantly. The experimental evidence supporting this model is as follows: Pure lymphocytic suspensions (PLS) are established and persist in culture when nude mouse-spleen and lymph-node cells are maintained on X-irradiated fibroblast monolayers in the presence of the S-phase cytotoxic agent cytosine arabinoside (Ara-C). From these PLS the following colony types can be initiated by the corresponding inducing (stimulating) factors (CSF): histiocytes (tissue macrophages) – CSF-1; granulocytes-macrophages (GM) – CSF-GM; mast cells – MMSF; granular-NK mucus secreting cells – IL-2; and multilineage colonies – IL-3. Mitotically active blast cells (formed by transformation of lymphocytes), condense into moti
