We noted that intestinal bacterial depletion in 5-month-old C57BL/6J mice did not have the same effect on the inflammatory modulation as in AD mice, and even promoted inflammatory activation (e.g., transcriptional up-regulation of Tnf-α, and down-regulation of Chi3l3) in the brain of 24-month-old C57BL/6J mice. Here, TNF is linked to Alzheimer disease.