[Relationship between the development of the intestinal IgA immune system and the establishment of microbial flora in the digestive tract of young holoxenic mice].

Abstract

The intestinal villi of axenic mice contain ten-fold less IgA plasmocytes than that of conventional ones. The major stimulus for proliferation of plasma cells synthetizing IgA in the gut of axenic mice is the total microbial flora from adult conventional mice. In young mice, the intestinal IgA immune system (intestinal IgA IS) is fully developed at the age of six weeks. The purpose of this work was to determine the role of intestinal flora on the development of the intestinal IgA IS. To that end, the complete digestive microflora from 1-25 day-old mice was transferred into adult axenic mice. The adult recipient mice harboured the same proportion of the same bacteria as the 1-4 day-old donor mice, Lactobacillus excepted. Thus, development of Lactobacillus is inhibited in recipient mice, whereas we did not observe any inhibition in young donor mice. For the 7-25 day-old donor mice, we still observed some resemblance between the flora of the donors and that of the recipients. However, the number of bacteria belonging to the genera Bacteroides and Eubacterium was larger in recipient than in donor mice. The microflora obtained from 1-23 day-old donor mice did not fully stimulate the development of the intestinal IgA IS of the recipient mice. In contrast, the microflora obtained from a 25 day-old mouse induced a full stimulation of the intestinal IgA IS in the recipient mice. Attempt to isolate the bacteria responsible for this complete stimulation were unsuccessful. We only know that these bacteria are present in a large proportion (10 8/g of faeces), that they are heat-sensible (70 degrees C, 10 min) and bacitracin-sensible. These results showed the important role of the sequential implantation of intestinal microflora in the development of intestinal IgA IS.