Early development of mast cells.

Mast cells originate from pluripotential cells in the bone marrow. Specifically, human mast cells originate from CD 34-positive progenitor cells. Mast cell proliferation requires IL-3. In the mouse, additional mast cell growth is achieved by the addition of IL-4, and GM-CSF prevents mast cell proliferation. Early bone-marrow-derived mast cells can be identified by their IgE receptors, although they may not yet have the characteristic morphology of mature mast cells. Whether these early cells may by themselves have a physiologic role, remains to be determined. Mast cells persist in culture on fibroblast monolayers, in part due to the production of soluble factor(s) from the fibroblasts themselves. Final mast cell phenotype appears dependent upon the local tissue environment.