Fig. 3. Mast cells degranulate in TrkA-deficient mice. Histological assessment of passive cutaneous anaphylaxis in control (A,C,E) and TrkA mutant (B,D,F) mouse ear sections stained for naphthol AS-D chloroacetate esterase. Compared with saline challenged mice (A,B), the IgE/DNP-treated mice (C-F) exhibited prominent mast cell degranulation and mixed inflammatory cell infiltrates. Arrows are directed to degranulated mast cells. (G) ß-hexoseaminidase release from bone marrow-derived mast cells obtained from TrkA mutant (TrkA^neo/neo) and control (TrkA^+/+) littermate mice was measured as described in Materials and methods. Mast cells obtained from the TrkA mutant mice show reduced ß-hexoseaminidase release relative to those from controls (^*P<0.01).