The dilemma of infection versus colonization at mucosal tissues: immunological and bacteriological features of obstructive tonsillar hypertrophy

Abstract

Immune responses at the boundary between the host and the world beyond are complex and mucosal tissue homeostasis relies on them. Obstructive sleep apnea (OSA) is a syndrome suffered by children with hypertrophied tonsils. We uncovered a crucial role of pro-inflammatory tonsillar B and T cells in sustaining hypertrophy and hyperplasia by producing TNF and IL17, respectively. We detected prominent levels of expression of CD1d by tonsillar stratified as well as reticular epithelium, which have not previously been reported. By combining bacterial culture from the tonsillar core and subsequent identification of the respective isolates, we determined the most prevalent species within the cohort of OSA patients. Although the isolated species are considered normal oropharyngeal commensals in children, we confirmed their capacity to breach the epithelial barrier. Our work shed light on the pathological mechanism underlying OSA, highlighting the relevance taken by the host immune system when defining infection versus colonization.