Memory B cell compartment constitution and susceptibility to recurrent lower respiratory tract infections in young children

[摘要] AproportionofchildrenhaverecurrentLRTIs,mostlyasaresultofSpn,whichpersistafter2yearsofage.Here,weinvestigate,byflowcytofluorometry,theconstitutionofthememoryBcellcompartmentin90healthychildrenand49childrenwithrecurrentLRTIstodetermineifanincreasedsusceptibilitytorecurrentLRTIsresultsfromadelayedorabnormalontogenywithpoorantibody‐mediatedprotection.TotalIgA,IgM,IgG,andIgGsubclassesweremeasuredbynephelometry,aswellasantipneumococcalantibodiesbyELISA.Pneumococcalvaccinationstatuswasobtained.WeshowthatthememoryBcellsincreasebetweenbirthand2yearsofage(1.6%vs.21.1%,P<0.001)withoutfurthersignificantincreasenotedperadditionalyears(3–4yearsold:23.3%;4–5yearsold:22.2%,P>0.40)toreachadult‐likevalues(31.8±11.8%,P=0.08).ProportionsofswitchedandIgMmemoryBcellsweresimilarinchildrenandadults.Comparatively,LRTIchildrenhadnodelayintheconstitutionoftheirmemoryBcellcompartment(2–3yearsold:26.9%;3–4yearsold:18.2%;4–5yearsold:26.8%,P>0.05).TheirswitchedandIgMmemoryBcellsweresimilaramongagecategories,andthedistributionwasoverallsimilartothatofhealthycontrols.LRTIchildrenhadnormaltotalandpneumococcalserotype‐specificantibodyvaluesbutshowedarapidwaningofantipneumococcalantibodylevelsaftervaccination.Insummary,ourresultsshowthatthememoryBcellcompartmentisalreadysimilarlyconstitutedat2yearsofageinhealthyandLRTIchildrenandthus,cannotexplaintheincreasedsusceptibilitytobacterialpneumonia.However,thewaningofantibodiesmightpredisposechildrentorecurrentinfectionsintheabsenceofrevaccination...

[学科分类] 生理学

[关键词] B‐lymphocyte subsets;immunologic memory;immunoglobulins;pneumonia;Streptococcus pneumoniae