Basophil activation by secreted substances from N brasiliensis. (A,C) β-hexosaminidase release from the basophil-like murine cell line IC-2 (A) or bone marrow–derived basophils (C) before (■) or after sensitization with serum from N brasiliensis–infected wild-type mice (□) or IL-4/IL-13–deficient mice (▩). Cultures were stimulated with antigen from total larval extract (NEX_L3) or secreted larval antigen (NES_L3), which were generated as described in Document S1. Control indicates samples that were sensitized but not exposed to antigen; TNP, samples which were sensitized with anti-TNP IgE mAb (□) or not (■) and stimulated with TNP-BSA as positive control. *P < .005. (B) β-hexosaminidase release from IC-2 cells that were either sensitized with serum from N brasiliensis–infected wild-type mice (□) or with anti-TNP IgE (▩) and stimulated with NES_L3. ■ indicates untreated controls. (D,E) IL-4 or IL-13 release from bone marrow–derived basophils after sensitization and stimulation as described in panel C. *P < .005. Bars show the mean plus SD from triplicate samples. n.d. indicates not detectable. The results are representative of 3 independent experiments. (F) Semiquantiative RT-PCR analysis of IL-4, IL-5, and IL-13 expression in bone marrow–derived basophils that were left untreated (control) or stimulated for 6 hours with NES_L3 (stimulated) after cells had been sensitized with serum from N brasiliensis–infected mice.