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A rabbit antiserum to the meconium antigen of the human fetal intestine is obtained by immunization of rabbits by this substance preparation. The preparation is extracted from meconium by the sulphate ammonium (70% saturation) treatment and gel filtration of supernatant with selection of the 240 kD fractions. In the indirect immunoperoxidase reaction the antiserum reacts with epithelium of certain normal and fetal tissues. It displays oncofetal features in colon, since it reacts with fetal and malignant epithelium and does not react with normal epithelium of this organ. The developed test-system may be used in pathomorphology for the morphological and functional state of colon mucosa evaluation.

Human tumours and tissues of nude mice were studied immunohistochemically using rabbit antibody to the beta-1-MA. Specific reaction was observed in colonic carcinomas, beta-1-MA was not found in other tumours. The specific reaction was found in intestinal epithelium of nude mice, and was absent in other tissues. 131I-labelled antibody to the beta-1-MA was intravenously administered to tumour-bearing nude mice. Specifically connected antibodies were revealed by immunohistochemical method in colonic carcinomas only. Radioimmunological investigation has shown accumulation of 131I-labelled antibodies to the beta-1-MA in colonic carcinomas.

Rabbit antisera to an organospecific intestinal antigen are obtained. This antigen has beta 2-electromobility, is thermolabile, is not extracted by perchloric acid and phenol and immunologically differs from CEA. The antigen is found in bottom zone of colonic crypt and in carcinomas of colon and rectum.