EARLY EXPRESSION OF HIGH-AFFINITY RECEPTOR FOR IMMUNOGLOBULIN-E (FC-EPSILON-RI) DURING DIFFERENTIATION OF MOUSE MAST-CELLS AND HUMAN BASOPHILS

Immediate hypersensitivity is due to the release of mediators from mast cells and basophils after the crosslinking of FcεRI. The appearance of such receptors was examined during differentiation of human and mouse bone marrow cells cultured in the presence of IL-3. As already reported, mouse bone marrow yield cultures of > 95% mast cells by 3 wk, whereas human bone marrow develop into cultures comprising 25% basophils by 3 wk. Here we show that transcripts for FcεRI subunits and membrane-associated receptors are apparent by 1 wk in both human and murine IL-3-dependent bone marrow cells. These cells contain few, if any, granules. The expression of transcripts and the number of receptor-positive cells continue to increase over 3 wk of culture. In parallel, a progressively larger number of cells become increasingly granulated to finally resemble either basophils or mast cells. Mature peripheral human basophils also contain transcripts for FcεRI and, therefore, may have the potential to synthesize de novo receptors. The early appearance of FcεRI during cell differentiation may be important for these cells to respond to IgE-mediated stimuli before granulation. The physiologic role of FcεRI could be to mediate lymphokine production (IL-3, IL-4, IL-6, and granulocyte/macrophage colony-stimulating factor) without inducing cellular degranulation.