A method for T-antigen demonstration by a polyclonal antibody and peanut lectin; elimination of cross-reaction with naturally occurring antibodies.

Antisera and a lectin were used to demonstrate T-antigens in colorectal carcinomas. Rabbits were immunized with red blood cells on which the T-antigen had been exposed. The obtained polyclonal antiserum and a crude lectin (PNA) prepared from peanuts were used in an immunoperoxidase technique. The crude lectin and a chromatographic pure lectin showed the same staining specificity. Different fixatives, length of fixation and buffer compositions were tested on paraplast and frozen sections. Four per cent formaldehyde preserved the antigens well in paraplast embedded tissues when fixation was shorter than 48 h. In the immunoperoxidase technique the chromatogen used was 3-amino-9-ethyl-carbazole whose staining intensity was sensitive to the H2O2 concentration. Agglutination of T-exposed red blood cells was used to assess the anti-T titre of various sera. Normal animal serum contained anti-T antibodies, and the possibility of false positive reactions and methods to avoid it in immunohistochemistry is discussed.