[Autostimulation of growth by murine myelomonocytic leukemia cells (WEHI-3B-Y1)].

We studied the effects of medium conditioned by WEHI-3B-Y1 (WCM) on the growth of the cells using serum-free culture. The growth of WEHI-3B-Y1 cells was stimulated by the addition of WCM in serum-free culture. Furthermore, WCM stimulated the proliferation of interleukin-3 (IL-3) dependent FDCP-2 cell line and contained burst-promoting activity when assayed on normal murine bone marrow. Recombinant murine IL-3 also stimulated the growth of WEHI-3B-Y1 cells in serum-free culture. These results indicate that WEHI-3B-Y1 cells cultured in a protein-free medium produce IL-3, which autostimulates the growth of the cells.