Can persistent nasal biofilms and mastoid fluid keep nearby mast cells primed?

Persistent pathological niches in the upper airway, such as bacterial biofilms and retained mastoid fluid, serve as active immunological engines rather than passive anatomical obstructions. This chronic state of localized irritation drives a continuous cycle of immune activation that directly affects adjacent mucosal tissues.

Epithelial activation and alarmin cascades

• Pathogen sensing: Biofilms, particularly those formed by Staphylococcus aureus, continuously release pathogen-associated molecular patterns (PAMPs) and secreted factors.
• Alarmin release: These factors stimulate epithelial pattern-recognition receptors (including TLR2), triggering the sustained release of epithelial alarmins such as thymic stromal lymphopoietin (TSLP), IL-33, and IL-25.
• Chronic fluid retention: In the middle ear and mastoid air cells, retained fluid maintains a localized pro-inflammatory microenvironment characterized by elevated TNF-α and IL-1β.

Mast cell infiltration and priming

• Th2 skewing: The resulting alarmin cascade establishes a localized, Th2-skewed inflammatory environment rich in IL-4 and IL-13.
• Cellular infiltration: These cytokines and biofilm-secreted factors directly promote the infiltration of mast cells into the adjacent nasal and airway mucosa.
• Receptor upregulation: This inflammatory milieu upregulates high-affinity IgE receptors (FcεRI) on mucosal mast cells. Constant exposure to local antigens and IgE cross-linking keeps these adjacent mast cells in a highly sensitized, "primed" state, making them hyper-reactive to minimal subsequent triggers.

Bottom line

• Persistent upper-airway biofilms and mastoid fluid drive chronic mucosal inflammation via epithelial alarmins (TSLP, IL-33, IL-25), which actively recruits, sensitizes, and primes mast cells in adjacent tissues, sustaining localized hyper-reactivity and airway symptoms.