Kiwifruit drives human microbiota-derived DNA to stimulate IL-7 secretion in intestinal epithelial cells

Intestinal immune tolerance is maintained through the interplay between commensal microbiota, immune cells and epithelium. Constitutive intestinal epithelial-secreted interleukin (IL)-7 facilitates the proliferation and thus maintenance of gamma-delta T lymphocytes, which preserves intestinal mucosal immune surveillance. Since IL-7 is essential for maintaining intestinal health, we hypothesised that microbiota-derived components influenced by dietary kiwifruit support the intestinal IL-7 expression. In vitro gastro-ileal digestion and colonic fermentation of gold and green kiwifruit generated soluble bacteria-free fermenta, notably bacterial DNA that modulated basal and interferon gamma-stimulated IL-7 secretion in HT-29 cells. Epithelial IL-7 secretion correlated positively with total bacterial DNA, and the DNA originated from bifidobacteria, which are known to contain immunostimulatory CpG motifs. These findings demonstrate the involvement of microbiota DNA in promoting IL-7 secretion in the intestinal epithelium and contribute to unravelling a mechanism by which kiwifruit serve to maintain intestinal immune homeostasis.