2.12. Passive cutaneous anaphylaxis (PCA)
C57BL/6 mice (6-8 week old) were locally sensitized with an intradermal injection of anti-DNP-specific IgE (100 ng/ear) into the right ear followed 24 h later by topical treatment with sophoricoside (3 or 30 mg/kg). Control mice were injected with the same volume of PBS and topically treated with 0.1% DMSO. One hour later, the mice were intravenously challenged with soluble antigen (100 µg DNP-HSA) in 100 µL PBS containing 5% Evans blue dye. One hour after antigen challenge, the dye was extracted from each dissected ear in 0.8 mL formamide at 65°C for overnight. The amount of extracted dye was measured spectrophotometrically at 620 nm and calculated from a standard curve established with known amounts of dye.