The association between chemically-induced intestinal
carcinoma and gut lymphoid patches was studied in 20 male Sprague-Dawley rats 7 months after the first of 16 weekly
injections of
1,2 dimethylhydrazine (
DMH). The lymphoid patches of
DMH-treated rats and of 14 untreated control animals were systematically studied histologically on sections of "swiss-rolled" whole intestine. It was found that 78% of the small-intestine
carcinomas and 73% of the
colorectal carcinomas were associated with intestinal lymphoid patches. Furthermore, misplaced and often atypical glandular crypts were often found in the parafollicular or interfollicular areas of lymphoid patches, in treated as well as in control animals. These glands could be the origin of the lymphoid-patch-associated
carcinoma. Immunohistological staining with
monoclonal antibodies (MAbs) against T-lymphocyte
antigens or
anti-IgM serum labelling B lymphocytes clearly localized early
carcinoma and atypical glands in the T-dependent, interfollicular and parafollicular area of lymphoid follicles. An MAb directed against
la-antigen stained some well-differentiated
carcinomas and some atypical glands found in control rats. On the other hand, lymphoid patches, when not invaded by a
carcinoma, were not modified in their number, size, morphology or cellular composition in
DMH-treated rats as compared to control animals.