The observation of reduced mucosal antibodies in the current study is in line with our prior data of decreased serum antibodies to Mcat proteins in sOP children during asymptomatic colonization, suggesting that sOP children had a deficient immune responses to Mcat. Stenfors and Raisanen found that there are less secretory IgA (sIgA)-coated bacteria in the nasopharynx of OP children, which may be responsible for the otitis-prone condition (33). The gene discussed is MCAT; the disease is ear infection.