Esterase staining of skin of the ear. Ear skin tissues from wild-type and TNFβ−/− mice were fixed in formalin and sections were stained with naphthol AS-D chloroacetate, N,N′-dimethylformamide, and hexazotized new fuchsin, pH 6.3. Arrowheads indicate esterase-positive cells. Estimated numbers of mast cells were 16.4 ± 1.4/field and 18.1 ± 3.2/field, respectively.