Figure 2

In vitro degranulation. Rat basophil leukemic cells expressing human FcεRI (RBL SX-38) were sensitized with 1 μg of IgE or buffer alone for 2 hours, followed by a 2-hour incubation with PSA, PSA-ACT, or HSA-PSA (an artificial PSA multi-epitope conjugate). The antigen concentration was adjusted to the equivalent molar amount of PSA-ACT (1 µg/mL or 0.1 µg/mL). The release of β-hexosaminidase into cell supernatants was monitored through the addition of 2.5 μM p-nitrophenyl-N-acetyl-β-D-glucosamine in 50 mM citrate buffer (pH 4.5). The mean and standard deviation of triplicate samples are shown. Data are representative of 2 independent experiments * p < 0.01 (Student’s t-test) compared to either component alone.