Nerve Injury-Induced Immune Responses in the Taste Bud Target Field

Damage to the chorda tympani (CT) nerve through trauma or experimental nerve axotomy results in the degeneration of anterior taste buds and taste loss. Our previous work demonstrated that Il1r signaling is required for taste bud regeneration and the recovery of taste function. However, the effects of experimental axotomy on immune responses in the absence of Il1r signaling remain unclear. To test this, we performed unilateral CT sectioning in Il1r KO or wild-type mice as previously described. We found that CD45+ immune cells, CD68+ and CD206+ M2-like macrophages are significantly increased near anterior taste buds at day two post-injury in wild-type but not Il1r KO mice. By day 5, these macrophage responses were slightly elevated in wild-type mice but remained at baseline levels in KO mice, indicating that immune responses to injury were suppressed rather than delayed in the absence of Il1r signaling. However, taste buds degenerated at similar time points in both strains. These results suggest that delayed taste bud degeneration in Il1r KO mice is not the primary reason for later functional deficits, though suppressed immune response may have other consequences in the injured peripheral taste system.