IgE antibodies may play an important role in noninfectious urinary inflammation, including interstitial cystitis (IC). In this study, urinary bladder strips were passively sensitized for 20 hours with serum from a ragweed-sensitive patient in the absence or presence of an anti-human IgE monoclonal antibody (MaE11) at 0, 1-, or 5-fold IgE concentration. The urinary bladder strips then were suspended in a superfusion apparatus for measurement of contraction and histamine release in response to antigen E (AgE) challenge. Non-sensitized tissues did not react to AgE challenge, whereas AgE challenge of passively-sensitized tissues resulted in time-dependent bladder contraction and histamine release. MaE11 abolished AgE-induced contraction and histamine release in a concentration-dependent manner. The safety of MaE11 was confirmed by its failure to contract or release histamine from passively-sensitized bladder tissues. The results of this study suggest that MaE11 may have immunotherapeutic benefit for amelioration of IgE-mediated diseases of the urinary system.