Frequency of circulating anti-GPIIb/IIIa antibody-producing B cells before and after administration of IDEC-131/E6040. Peripheral blood B cells producing IgG anti-GPIIb/IIIa antibodies were quantified by using an enzyme-linked immunospot assay, and the results represent the mean of the 5 values (number per 10⁵ PBMCs). Peripheral blood samples were analyzed at 3 different time points: day 0 (pretreatment; Pre), and days 7 and 42 after treatment (7P and 42P, respectively). Statistically significant change compared with pretreatment is indicated by < (P < .05 by repeated measures analysis of variance). In the 10 mg/kg group, ○ indicates responder and • indicates nonresponder.