ROLE DU SYSTEME IMMUNITAIRE DIGESTIF DANS LE CONTROLE DE LA TRANSLOCATION BACTERIENNE CHEZ LA SOURIS GNOTOXENIQUE

The aim of this work was to study the role of gut associated lymphoid tissue in the control of bacterial translocation. Two strains of Escherichia coli were orally inoculated into 71 axenic mice. Ten days later, the 2 initial strains and 2 others, resulting from plasmidic exchanges, were present in the digestive tract of the mice which were divided in to two groups: the first group (n = 41) received one intraperitoneal injection of cyclophosphamide 100 mg/kg; the second control group (n = 30) received isotonic saline. The following parameters were studied 3, 5 and 9 days after the injection: the population level of the 4 strains in the caecum, their translocation to mesenteric lymph nodes, liver, spleen and circulating blood, the density per unit surface of lamina propria plasma cells and intraepithelial lymphocytes in duodenal and caecal mucosa. The population in each strain found in the caecum was different from the 3 others but similar within the two groups of animals and remained unchanged with time. In the control group, bacterial translocation to the mesenteric lymph nodes decreased (p < 0.01), while the density of plasma cells increased (p < 0.01) from the 3rd to the 9th days. The cyclophosphamide treated group, translocation to the mesenteric lymph nodes increased (p < 0.01), while the density of intestinal plasma cells decreased (p < 0.05) from the 3rd to the 9th days. Density of intraepithelial lymphocytes did not vary with time each group and from one group to another. Bactertial translocation to liver, spleen and systemic blood was weak and did not increase in the treated group. These results suggest that plasma cells of the lamina propria play a role in the control of the first step of bacterial translocation from the intestine.