Differences in the sensitivity of normal human peripheral blood and bone marrow granulocytic-macrophagic and eosinophilic colony forming cells (CFC) to a source of colony stimulating factor.

The relative sensitivity of normal human peripheral blood (PB) and bone marrow (BM) granulocytic-macrophagic and eosinophilic committed stem cells (CFC) to a source of colony stimulating factor (CSF) was evaluated. In this study, PB and BM cells depleted of mature granulocytes, monocytes (Mo), thymus dependent lymphocytes (T cells), and, in some studies, bone marrow derived lymphocytes (B cells) were cultured in soft agar medium. Human placental conditioned medium (HPCM) was used as a source of CSF. The time sequence evaluation of cultures of PB and BM cells in the presence of a constant amount of HPCM confirmed the results of earlier culture studies of unseparated PB and BM nucleated cells which showed that the proliferation of PB CFC is maximum at or after days 14 to 15 and that of BM CFC at days 7 to 8. Culture of a constant number of PB and BM cells with variable amounts of HPCM indicated that PB CFC require an exogenous source of CSF for proliferation whereas BM CFC proliferate to a modest degree in its absence. The rate of increase in the number of CFC proliferated with the addition of increasing amounts of HPCM is higher for BM than for PB. These data indicate that the BM CFC are more sensitive to a source of CSF than are the PB CFC. Also, the results of this study, along with those in the literature, support the concept that the PB and BM CFC comprise distinct populations, and, further, suggest that the PB CFC is more primitive than the day 7 BM CFC.