Effects of intestinal bacteria on the development of colonic neoplasm II. Changes in the immunological environment

To study the effects of intestinal bacteria on the development of colonic n eoplasm, we have established gnotobiotic mice with a single species of inte stinal bacteria, In the previous study, the incidence of colonic adenoma in duced with 1,2-dimethylhydrazine (DMH) in the gnotobiotic mice with Lactoba cillus acidophilus, gnotobiotic mice with Escherichia coli and germ-free mi ce were 30, 50 and 74%, respectively. In this study, 7-week-old mice in eac h group were sacrificed without the administration of DMH to examine the co nstituents of immune-competent cells in various mouse organs using flow cyt ometry, In the gnotobiotic mice, CD3 intermediate interleukin (IL)-2R beta positive cells were observed predominantly in the liver, In the gnotobiotic mice with L, acidophilus, Mac-1 positive Gr-1 positive cells were observed predominantly in the colonic lamina propria, The activation of extrathymic T cells in the liver and granulocytes in the colonic mucosa may be related to anti-neoplastic effects of L, acidophilus in this experimental model. ( C) 1999 Lippincott Williams & Wilkins.