Langerhans Cells Regulate Tongue Intraepithelial Innervation in a Microbiota- and Age-Dependent Manner

Oral Langerhans cells (LCs) are well recognized for their immunological roles, but their involvement in other physiological processes remains poorly understood. This study identifies a novel function of oral LCs in regulating tongue epithelial innervation. Postnatal LC development coincides with the establishment of local innervation, and LC depletion impairs innervation and alters nociceptive responses, underscoring their neuroimmune function. This function is driven by LC-derived IL-1β, which stimulates basal epithelial cells to produce nerve growth factor (NGF), thereby promoting sensory nerve growth. Transcriptomic analyses revealed neuronal-related pathways enriched in LCs. Aging reduces LC frequency, NGF expression, and epithelial innervation, linking neuroimmune regulation to epithelial aging. While LC frequencies in the tongue remain unaffected in germ-free mice, the microbiota is essential for optimal LC function and NGF production. These findings expand our understanding of oral LCs, revealing their pivotal role in epithelial innervation beyond immune surveillance.