Development of the intestinal microbiota in rats and its possible interactions with the evolution of the luminal IgA in the intestine.

Abstract The development of the intestinal microbiota in rats from 18 to 40 days old was analyzed by monitoring 16S ribosomal DNA diversity in fecal samples by polymerase chain reaction temperature gradient gel electrophoresis (PCR-TGGE) combined with hierarchical clustering analysis. The evolution of the fecal IgA was also analyzed by an additional experiment. There were two events for the diversification of the intestinal microbiota from suckling to maturity. The first change occurred between days 21 and 22 after birth, and the diversity showed a remarkable increase at this time. The second change occurred from days 24 to 27, and the increase in the diversity of the intestinal microbiota ceased. The amount of fecal IgA decreased from days 18 to 22 and remained low until day 24. On day 27, it recovered and continued to increase. This study suggests the possible interactions between the development of the intestinal microbiota and the evolution of the intestinal SIgA. The decline in maternal IgA supply as the suckling period proceeded allowed the bacterial colonization. As a consequence of this increase in bacterial colonization, the secretion of the self-SIgA was accelerated in pups.