Effect of gut-associated lymphoid tissue on cellular proliferation in proximal and distal colon of the rat.

In previous studies, chemically induced colonic carcinomas were found to originate preferentially from crypts adjacent to lymphoid tissue. Proliferative parameters and mucosecretion were analyzed in proximal and distal rat colon in relation to the proximity of lymphoid patches. Animals received an intraperitoneal pulse of bromodeoxyuridine 1-hr before death. In both proximal and distal colon, crypts located at the immediate proximity of the lymphoid formations contained fewer mucous cells (P less than 0.001), but a higher percentage of proliferative epithelial cells (P less than 0.001) than the crypts far from lymphoid formations. The labeling index was higher in crypts adjacent to lymphoid patches compared to crypts distant from lymphoid patches only in the lower third of the crypts. The association of an increased proliferative activity and a decrease in differentiated mucosecreting cells in colonic crypts adjacent to lymphoid patches could be related to the particular sensitivity of these crypts cells to the effects of mutagens and carcinogens.