Vivo Regulation of FceRI on Human Basophils

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The implication of these functionai studies is that shifts in receptor occupancy by allergen-specific IgE could restore basophil mediator reiease. Further support for this hypothesis was obtained from iater portions of the same phase I E25 trial. After 28 weeks of biweekly infusions, subjects were randomized to receive a 3 to 20-fold reduction in E25 dosing and continued for another 18 weeks. The result of this reduction was an increase reflected in free serum IgE levels from a mean of 7 ng/mL at week 28 to approximately 21 ng/mL at the termination of infusions (68). By the end of this treatment period, the ievels of basophii surface IgE expression and FceRIa rose three- to fourfoid, with the average number of receptors per basophil rising to nearly 35,000 per cell at the 

In the last part of this study, subjects were followed for up to one year after their final dose of E25 to examine restoration of serum IgE levels, basophil phenotype, and basophil function (68). As previously noted, due to the dosage reduction introduced in the latter half of infusions, basophil function was nearly restored, with only a slight rise in circulating free IgE and basophil receptor numbers by the last day of infusion. Diuing the first 8 weeks post-treatment, free IgE levels rose nearly fivefold, while basophil surface IgE and EceRIa rose 2.7-fold and 2-fold, respectively (Fig. 3). 

In Vitro Regulation of FceRI on Human Basophils from Treated Subjects 

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