Immune responses of palatine tonsil against bacterial antigens

Background: Although various bacterial antigens are frequently found in upper respiratory tract mucosal secretions, fatal responses, such as endotoxin shock, are rare, suggesting the presence of some regulatory system in mucosal as well as systemic tissues. In the present study, we examined the immune responses of tonsillar mononuclear cells against bacterial antigens. Materials and methods: Mononuclear cells were isolated from the palatine tonsils and peripheral blood (tonsil mononuclear cells [TNMC] and peripheral blood mononuclear cells [PBMC]) of patients who underwent palatine tonsillectomy. TNMC and PBMC were stimulated using lipopolysaccharide (LPS) or lipoteichoic acid (LTA) for 24 h, and cytokine production were determined by ELISA. Furthermore, the expression of Toll-like receptor (TLR) 4 and TLR2 on CD14+ and CD11c+ cells were examined by FACS. Results: The production of TNFα, IL-1β, IL-6 and IL-8 from TNMC after stimulation with LPS or LTA were significantly lower than those from PBMC. Although CD11c+ cells were observed in both TNMC and PBMC, the incidence of TLR4 or TLR2 expressing cells was lower in TNMC than in PBMC. Conclusions: Results suggest that the decreased expression of TLR4 and TLR2 in TNMC might be associated with the hyporesponses of palatine tonsils against LPS and LTA.