Characterization of the target cell receptor for IgE—I. Solubilization of IgE-receptor complexes from rat mast cells and rat basophilic leukemia cells

Purified rat monoclonal IgE was labeled with 125I and allowed to interact with either purified rat mast cells (RMC) or rat basophilic leukemia cells (RBL). Virtually 100% of the cell bound 125I-IgE was solubilized by treating the cells with buffer containing 0.5% Nonider P-40. When this solubilized IgE was subjected to gel filtration it was found to elute ahead of free IgE or IgE which had been allowed to interact with control (non-IgE binding) cells, indicating that at least a portion of the cellular IgE receptor remained attached to the IgE. The IgE-receptor complexes isolated from either cell type eluted at almost identical volumes, and a comparison with polymeric IgA suggested that they had a mol. wt of 3·5–5·5 × 10 5 daltons. Complex formation also occured if cells were solubilized prior to the addition of IgE. Soluble cell extracts from both RMC and RBL cells caused inhibition of passive cutaneous anaphylaxis, however, the inhibition was less efficient than that given by comparable numbers of intact cells.