To explore the role of the M cells in AD microenvironments, we investigated changes for brain and gut environments using AD-mimicked mice (5xFAD and 5xFAD-FMT) and M cell-depleted AD-mimicked mice (5xFAD/Spib−/− and 5xFAD-FMT/Spib−/−). Here, SPIB is linked to Alzheimer disease.