IL4 and neoplasm: Although the priming of U937 cells with IL-4 was required to induce significant expression of the low-affinity FcεRII receptor for IgE binding in this model in vitro, tumor cell killing by IgE-mediated ADCC does not require administration of IL-4.15,34 Whether IgE immunotherapy may be primed in Th2 environments requires further investigation.