CONICET | Buscador de Institutos y Recursos Humanos

Tonsils are secondary lymphoid organs with predominance of B cells (Bc), located in the isthmus of the fauces. We have previously shown a role for the regulatory Bc subset in controlling germinal center responses in human tonsils and the impact of their malfunction on tonsillar size (hypertrophy). Obstructive sleep apnea (OSAS) is a syndrome suffered by children with hypertrophied tonsils. As tonsils comprise mucosal lymphoid tissue, constantly exposed to the environment, it is difficult to distinguish bacterial infection versus normal colonization.Therefore, the involvement of pathogenic bacteria in hypertrophy is controversial. Our objective was to build up a comprehensive picture of hypertrophied tonsils in terms of their microbiome, histology and Bc cytokine response. Using immunofluorescence (IF) on criosections, we discovered CD1d and Ecadherin expression in tonsillar epithelium (lymphoid compartment was evidenced with anti IgG, IgM and IgA). Such epithelial staining allowed us to determine that all samples analyzed by IF presented barrier disruptions. Upon culture of 21 surgical samples and subsequent identification by MALDI-TOF MS, we found that Streptococcus pyogenes group A (isolated from 29% of patients), Staphylococcus aureus (24%) Haemophilus influenzae (24%) were the most prevalent bacteria within our cohort of patients. By fluorescence in situ hybridization, we could identify spatially organized bacterial aggregates in biopsies. Finally, we determined Bc intracellular expression of inflammatory cytokines (IFN-γ,TNF-α and IL17) by FACS. In conclusion, we postulate that hypertrophy constitutes a local symptom of an active infection of well-defined species characterized by barrier disruption, lymphocyte infiltration and inflammatory cytokine response.