We previously postulated that desensitization of human basophils was due to endocytosis or shedding of IgE and/or its Fc receptor. We report here, however, that during a 3-hr desensitization of purified basophils, there was no loss of cell surface antigen-specific IgE. The specific desensitization induced by antigen persists for at least 24 hr whereas simultaneously occurring nonspecific desensitization can recover during the same time interval. Therefore, we suggested that specific desensitization may result from a permanent modification of the Fc receptor or some closely associated protein. On the basis of elution studies of 125I-labeled BPO-HSA, we also suggest the antigen antibody reaction matures to aggregates of increasing size, and we propose that these large aggregates, unable to initiate a release signal, cause an additional component of desensitization.

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