Here, we address the long-standing question of how benign gut microbes evade the immune system. We identified a new type of flagellin in the human gut, termed ‘silent flagellin,’ that binds to the immune receptor Toll-like receptor 5 without inducing a pro-inflammatory response. The findings provide a mechanism for the immune system to tolerate beneficial microbes while remaining responsive to pathogens.

Clasen SJ, Bell MEW, Borbón A, Lee DH, Henseler ZM, de la Cuesta-Zuluaga J, Parys K, Zou J, Wang Y, Altmannova V, Youngblut ND, Weir JR, Gewirtz AT, Belkhadir Y, Ley RE. Silent recognition of flagellins from human gut commensal bacteria by Toll-like receptor 5. Science Immunology eabq7001. (2023)