Influence of changes in the intestinal microflora on the immune function in mice

The composition of the intestinal microbiota is related to the health and immune function of the host. Administration of antibiotics affects the composition of the intestinal microbiota. However, the effects of immune function on the composition of the intestinal microbiota are still unclear. In this study, we investigated the lymphocyte composition and determined the relationships between lymphocyte function and the intestinal microbiota following antibiotic treatment in mice. To change the composition of the intestinal microbiota, mice were treated with or without antibiotics. Analysis of intestinal microbiota was performed by metagenomic analysis targeting 16S rRNA. Lymphocyte subsets of splenocytes were measured by flow cytometry. For functional analysis of T cells, splenocytes were stimulated with concanavalin (Con A), and cytokine gene expression was measured by real-time polymerase chain reaction. Firmicutes were predominant in the control group, whereas Bacteroidetes predominated in the antibiotic-treated group, as determined by metagenomic analysis. The diversity of the microbiota decreased in the antibiotic-treated group. Analysis of lymphocyte subsets showed that CD3(+) cells decreased, whereas CD19(+) cells increased in the antibiotic-treated group. All cytokine genes in splenocytes treated with Con A were downregulated in the antibiotic-treated group; in particular, genes encoding interferon-gamma, interleukin (IL)-6, and IL-13 significantly decreased. Taken together, these results revealed that changes in the composition of the intestinal microbiota by antibiotic treatment influenced the population of lymphocytes in splenocytes and affected the immune response.