CONDITIONED MEDIA FROM A CELL STRAIN DERIVED FROM A PATIENT WITH MASTOCYTOSIS INDUCES PREFERENTIAL DEVELOPMENT OF CELLS THAT POSSESS HIGH-AFFINITY IGE RECEPTORS AND THE GRANULE PROTEASE PHENOTYPE OF MATURE CUTANEOUS MAST-CELLS

We have demonstrated for the first time that a conditioned medium from a human cell strain can induce morphologically mature mast cells that express Fc epsilon RI and three mast cell-specific proteases from nor mal bone marrow progenitor cells. In contrast, recombinant human Kit l igand induced the differentiation of mast cells that were tryptase-pos itive but negative for chymase, carboxypeptidase, and Fc epsilon RI. T his data indicates that factors other than Kit ligand are critical for inducing the differentiation and maturation of mast cells in the huma n. The HBM-M cell was originally derived from a patient with mastocyto sis, As mastocytosis is thought to represent a reactive hyperplasia ra ther than a mast cell malignancy, the factor secreted by the HBM-M cel l strain could well be responsible for the mast cell hyperplasia seen in some patients with mastocytosis.