Signaling Pathways Activated in a Unique Mast Cell Line Where Interleukin-3 Supports Survival and Stem Cell Factor Is Required for a Proliferative Response

Stem cell factor (SCF) and interleukin-3 (IL-3) both act on several target hematopoietic populations, including mast cells. We have isolated a unique murine mast cell line, B6M. that is phenotypically similar to immature mast cells. For B6M cells, IL-3 is a survival factor and alone does not stimu-late proliferation. SCF can stimulate proliferation of B6M cells, and together IL-3 and SCF synergize to stimulate opti-mal proliferation and long-term growth. A sustained induc-tion of c-myc is observed only in the presence of SCF (with or without IL-3). In B6M cells, both IL-3 and SCF stimulate phosphorylation of Shc and activation of the Ras, Raf-1, NTERLEUKIN-3 (IL-3) acts on a wide range of hemato- I poietic cell types and can regulate cell survival, prolifera-tion, development, and functional activity. Mast cells are a major target of IL-3 in mice, and many IL-3-dependent mast cell lines have been established. Mature mast cell