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The sections were then incubated at 37°C in a humidified chamber for 90 min with 100 |xl of primary antibody diluted in Tris-buffered saline (TBS). Following washes in 0.1% Tween20 in TBS, the slides were incubated with secondary antibody (1:250; 100 |xl) labeled with horseradish peroxidase for 30 min at 37°C in a humidified chamber Reactions were revealed with dia-minobenzidine tetrahydrochloride (DAB). Sections were counterstained with methylene blue, dehydrated in ethanol and Histoclear, and mounted with cover slips using Permount. TBS substitution for primary antibody was used as a negative control. No reactions were observed in these sections. For the anti-ABP antibody, paraffin sections were processed for im-munostaining using the ImmunoCruz ABC Staining System (Santa Cruz Biotechnology Inc., Santa Cruz, CA). The sections were deparaffinized and hydrated as described above. Sections then were microwaved for antigen retrieval in citrate buffer. After boiling and cooling, the ImmunoCruz system was employed as per the suppliers’ instructions. Sections were incubated with the anti-ABP antibody at a dilution of 1:100 overnight at 4°C. The sections were then washed in phosphate buffered saline (PBS) and incubated in biotinylated secondary antibody (1:250) for 30 min at room temperature. Sections were washed again in PBS and incubated in an avidin-biotin-horseradish peroxidase solution for 30 min at room temperature. Reactions were visualized by DAB. The sections were counterstained with methylene blue, dehydrated, and mounted with cover slips. For negative controls, normal blocking serum was substituted for primary antibody; no reactions were detected in the epithelium.