IgE antibody up-regulates high affinity IgE binding on murine bone marrow-derived mast cells

We have examined 3-week-old alcian blue positive cells (putatively mast cells) derived from mouse bane marrow for their expression of FcεRI. Using an indirect method of sensitizing the cells with immunoglobulin E (IgE) antibody (anti-DNP IgE) and detecting the level of bound IgE antibody by flow cytometry, we found that prolonged culture (1-5 days) with IgE, but not IgG, increased the total receptor density 6 ± 1.9 fold. During the same period, histamine release in response to antigen (DNP-HSA) increased approximately 6-fold while the cell's response to either thrombin or ionomycin remained constant. The greatest up-regulation occurred in the first 2 days of culture. Using 2.4G2 to detect FcγRII/RIII, we could not detect any up-regulation of this receptor. Culturing the cells for I h after sensitization did not result in any loss of cell surface IgE, suggesting a reasonably high affinity binding similar to that expected for FcεRI. This up-regulation was completely inhibited by co-culture with 2 μg/ml cycloheximide. These data suggest that IgE is capable of inducing a significant, protein synthesis, dependent up-regulation of its own high affinity receptor on mast cells/basophils.