[Association between intestinal flora and immunity in middle-aged and aged people by PCR-DGGE]

To analyze whether the effects of the aging caused changes in intestinal flora to the immunity by evaluating the potent association between the intestinal flora and their immunity of middle-aged and aged healthy subjects based on profiling the composition of their fecal bacteria and testing their immune parameters.

Total 99 healthy volunteers aged 50- 75 were recruited. Blood samples collected from them were analyzed for CD3~+T cell, CD4~+T cell, CD8~+T cell, serum Ig A, Ig M and Ig G with flow cytometer( FCM) and immunoturbidimetry. The fecal samples were also collected from them. The genomic DNA of fecal bacteria was extracted and amplified with the universal primers of bacterial 16S rRNA V6- V8 region by PCR. The DNA amplifications were tested with denaturing gradient gel electrophoresis( DGGE). Cluster analysis, principal component analysis( PCA) and variance analysis were used to characterize fecal bacteria composition andanalyze the association with observed immune parameters.

The fecal microbiota were highly polymorphic and greatly varied among the tested subjects. CD3~+T cell and CD4~+/CD8~+ levels correlated with intestinal flora structure. Intestinal flora richness( S) of population with high CD4~+/ CD8~+ level was lower compared with population with normal or low CD4~+/ CD8~+ level. However, no apparent association was observed between serum Ig A, Ig M, Ig G levels and the fecal microbiota among the tested subjects.

The decrease in the diversity of intestinal flora might affect CD8~+T cell based innate immunity of host. The deep association could exist between intestinal flora and their immunity in middle-aged and aged people.