Distribution and differentiation of murine mast cell progenitors determined with soft agar culture

We have examined the distribution and differentiation of mast cell progenitors (mast-CFC) using a sensitive semisolid agar culture stimulated with STIL-3 (leukemic T cell line)-conditioned medium as a source of interleukin 3. The number of mast-CFC in the bone marrow of normal (+/+) mice was much higher than in previously reported data, although the number was almost the same in the spleen and peripheral blood as in previously reported data. Although mast-CFC were detectable in genetically anemic W/Wv mice as well, the concentration in the bone marrow was significantly lower than that of the +/+ mice. In the bone marrow there were more immature mast-CFC forming large-sized colonies (greater than 500 cells), whereas these were very few in the spleen and peripheral blood. Most mast-CFC were in the resting state. We conclude that mast-CFC differentiate to some extent in the bone marrow and then migrate in the peripheral blood to some organs where they proliferate and differentiate.