ESTABLISHMENT OF A MURINE PRE-B-CELL CLONE DEPENDENT ON INTERLEUKIN-7 AND STEM-CELL FACTOR

To identify cytokines required for proliferation of murine pre-B cells, we established a pre-B cell clone MH11 (B220+ MB-1+ sIgM-) on a stromal cell line ST2 from day 13 fetal liver. The growth of MH11 is dependent on ST2. Another stromal cell line PA6, non-secretor of IL-7, could not support MH11 unless IL-7 was added. We investigated the effect of cytokines on proliferation of MH11 with or without stromal cells. IL-7 had a stimulatory effect on proliferation of MH11, but IL-7 alone could not support MH11 growth without ST2. Recombinant stem cell factor (rSCF) also had a positive effect on MH11. rSCF and rIL-7, when added together, could maintain the growth of MH11 in the absence of stromal cells. Moreover, the growth of MH11 on ST2 was inhibited almost completely by anti-c-kit monoclonal antibody (mAb). These results demonstrate that direct SCF/c-kit interaction is involved in the stimulation of pre-B cells.