Innate immune system is implicated in recurrent aphthous ulcer pathogenesis

Abstract Background: Recurrent aphthous ulcers (RAU) is a chronic inflammatory disease with evidence of inappropriate immune response. This study presents the status of innate immune system in RAU. Methods: Twenty RAU patients and 19 healthy individuals were selected. The status of peripheral blood neutrophils (reactive oxygen intermediates (ROI) production, CD11b, TNF‐RI and TNF‐RII expression), concentration of antioxidants, sTNF‐R, C3c, C4 and haemolytic activity of the complement system, as well as mannose‐binding lectin (MBL), in the serum of RAU patients in active stage and in remission of the disease were determined. Results: Peripheral blood neutrophils were primed in RAU, which resulted in increased ROI production by resting and fMLP‐stimulated neutrophils and diminished ROI production after in vitro priming. The increased expression of CD11b on resting and fMLP‐stimulated neutrophils in RAU may also point to their previous in vivo stimulation. The decreased total antioxidant status of serum observed in RAU may be a result of increased ROI production by peripheral blood neutrophils. The levels of C3c, C4 and haemolytic activity of the complement system were higher in RAU than in healthy people. No significant differences between active and remission RAU were noted. Conclusion: Presented observations confirm that the innate immune system is involved in RAU pathogenesis.