Investigation The Relationship Between Treg And Streptococcus Pneumoniae Colonization In Adnoid Of Children

Background and Objective: Streptococcus pneumoniae is theprimary pathogen results in died in children under5years of age.Asymptomatic nasopharyngeal carriage is a common precursor to invasivedisease. Although anticapsular antibodies showed the importance ofhumoral immunity as one mechanism of protection against colonizationand disease from S. pneumoniae, but host can clear bacteria before theseantibodies appear, and studies in adults have found little or no evidence thathigher anticapsular antibody concentrations have greater protection fromcolonization, suggesting involvement of other mechanisms. Recent studieshave demonstrated the CD4+T cells play an important role in localimmunity, especially Th17cells and the cytokine IL-17. TH17cells confersprotection against experimental colonization via release neutrophilactivating cytokine IL-17A. IL-17A increased pneumococcal killing byhuman neutrophils both in the absence and in the presence of antibodiesand complement. However, a recent study reported that the inactivatedstreptococcus pneumoniae and the component of streptococcus pneumoniae capsular can induce the Treg cells, Treg cells have a strongimmunosuppressive effect, can inhibit the function of effector T cell.Nasopharyngeal adenoids are mucosa-associated lymphoid tissue whichplays important role in clearing the streptococcus pneumoniae. So thisstudy aim to explore the mechanism of Treg cells in pneumococcalcolonization in adnoid of children.Methods: Collect the swabs of children （3-8year） undergoadenoidectomy,then culture bacterial of swabs to identify if there is agrowth of streptococcus pneumoniae. Meanwhile gather the adnoid toseparate the mononuclear cells to detect the percentage of Foxp3+Treg andTh17cells in CD4+T cells by flow cytometry. Fluorescence quantitativePCR detect the expression of Foxp3-mRNA and RORγt-mRNA inmononuclear cells of adnoid. The mononuclear cells of adnoid was coculturewith CCS（1μg/ml） for24h, then detect the percentage of Foxp3+Treg andTh17cells in CD4+T cells by flow cytometry and detect the expression ofFoxp3-mRNA and RORγt-mRNA by fluorescence quantitative PCR.Adenoidectomy mononuclear cells with streptococcus pneumoniae culturesupernatant concentrate (CCS)1μg/ml trained for24hours.Results: A total of30patients were recruited into the study, andpneumococcal carriage rates were30%assessed by pneumococcal culture ofnasopharyngeal swabs. No difference was found in carriage rates betweenmales (n=17) and females (n=13)(29.4%and30.8%, respectively). The percentage of Foxp3+Treg in CD4+T cells and the expression ofFoxp3-mRNA in mononuclear cells of adnoid was higher in culture positiveof pneumococcal than culture negative（6.70%vs4.49%P＜0.001；2.15vs1.01，P＜0.05）, The percentage of Th17in CD4+T cells and the expressionof RORγt-mRNA was lower in culture positive of pneumococcal thanculture negative（1.70%vs3.84%P＜0.05；0.19vs0.52，P＜0.01）. Themononuclear cells of adnoid was coculture with CCS（1μg/ml） for24h, wetest the increase of the percentage of Foxp3+Treg in CD4+T cells and theexpression of Foxp3-mRNA in mononuclear cells of adnoid wassignificantly higher in culture positive of pneumococcal compared withculture negative（3.37%vs1.54%P＜0.01；0.97vs0.14，P＜0.05）,theincrease of the percentage of Th17cells in CD4+T cells and the expressionof RORγt-mRNA was obviously lower in culture positive of pneumococcalthan culture negative（2.22%vs3.4%；0.03vs0.44，P＜0.05）.Conclusion: The colonization of streptococcus pneumoniae in nasalassociated lymphoid tissue will induced the increase of Treg which mayinhibit the Th17cells clearing the streptococcus pneumoniae result inpersistently carriage of streptococcus pneumoniae.