Lung Migratory CD103~+ DC Suppresses Generation Of Allergen-specific Th2 Memory Cells

Objective:Memory Th2 cells play critical roles in allergic asthma.Its generation and main-tenance could be regulated by several signal pathways.Dendritic cells（DC）socalled professional antigen-presenting cells（APC）,play pivotal roles in T cell-mediated adoptive immunity.Data suggested that different lung dendritic cell（DC）subsets preferentially induce na（?）ve CD4⁺T cells polarize to distinct Th1 or Th2 subsets.However,the roles of lung DC subsets in generation and maintenance of memory CD4⁺T cells（CD4⁺T_M）is still unclear.Based on previous studies,we establish a murine model of allergen-induced Th2-type allergic asthma.Using modern immunological techniques combined with transgenic and gene knock-out mice,we aims to clarify the division labor and crosstalk between lung DC subsets in generation and maintenance of CD4⁺T_M.Furthermore,we try to elucidate possible underline mechanisms of lung DC subsets in regulating CD4⁺T_Mgeneration and maintenance.This study will be helpful to obtain a deeper understanding of the mechanism in allergic asthma pathogenesis,and will providenew insights into vaccine design for allergic asthma.Methods:1.Na（?）ve CD45.1⁺OT-II cells were adoptively transferred into congenically distinct normal C57BL/6（WT）and Batf3^-/-mice,and recipients were immunized with OVA/papain24 hr later.The generation of CD45.1⁺CD4⁺T_M cells in lung draining lymph nodes（d LNs）were explored at 40 days after immunization.2.Bone-marrow chimera WT and Batf3^-/-mice were injected with na（?）ve CD45.1⁺OT-II cells through tail vein,and were immunized with OVA/papain after resting for 1 day.To clarify the roles of CD103⁺DC deficiency in generation of CD4⁺T_M cells,count and phenotype of CD45.1⁺CD4⁺T_M cells in d LNs,inguinal lymph nodes（i LNs）and spleens of WT and Batf3^-/-mic were investigated 40 days after immunization.3.Single cell suspensions from d LNs of BM chimera WT and Batf3^-/-mice were prepared 40 days after immunization when CD45.1⁺CD4⁺T_M cells had been generated,and were injected into B6 mice.Recipients were rechallenged with OVA twice and examined for recall responses of CD45.1⁺CD4⁺T_Mcells.4.Activated CD45.1⁺OT-II cells primed in dl Ns of chimera WT and Batf3^-/-mice were equally transferred into C57BL/6 recipient mice which were pre-immunized with OVA/papain 5 days before.After resting for 1 day,recipients were reboosted twice every other day,and were rechallenged at 40 days after immunization to induce recall responses.On the other hand,Langerin-DTR mice were injected with na（?）ve CD45.1⁺OT-II cells,and were treated with diphtheria toxin（DT）twice to deplete CD103⁺DC during priming phase,and the generation of CD45.1⁺CD4⁺T_M cells was investigated 40 days after immunization.Our aim was to confirm that CD103⁺DC and CD11b⁺DC dictated the fate decision of CD4⁺T cells between effector and memory cells during priming phase.5.Activated CD45.1⁺OT-II cells were sorted from d LNs of chimera WT and Batf3^-/-mice 5 days after immunization with OVA/papain,and were equally injected into B6recipients which was immunized with OVA/papain 5 days before.After resting for 1 day,recipients were reboosted twice every other day,exaimined for the expansion and phenotype of CD45.1⁺OT-II cells.6.Bone-marrow chimera WT and Batf3^-/-mice injected with na（?）ve CD45.1⁺OT-II cells and were immunized with OVA/papain after resting for 1 day,and were examined for frequency,count,proliferation,apoptosis,migration and phenotype of activated CD45.1⁺OT-II cells 5 days after immunization.Results:1.More CD45.1⁺CD4⁺T_M cells were generated in d LNs of Batf3^-/-mice than that of WT mice.2.CD103⁺DC deficiency promoted generation of circulating CD4.51⁺Th2 memory cells,and the proportion of T_CM(CD44^hiCD62L⁺)and T_EM(CD44^hiCD62L^-)cells in d LNs were comparable between chimera WT and Batf3^-/-mice.There was no T_RM(CD44^hiCD69⁺CD62L^-)cells detected in lungs of WT and Batf3^-/-mice during this OVA/papain induced asthma model.3.CD45.1⁺CD4⁺T_M cells primed in absence of CD103⁺DC could be re-activeted after re-challenge with OVA.4.Activated CD45.1⁺OT-II cells primed in d LNs of Batf3^-/-mice prefered to generate Th2 memory cells.5.CD45.1⁺OT-II cells primed in absence of CD103⁺DC had greater potential to proliferate.6.Activated CD45.1⁺OT-II cells primed in CD103⁺DC deficient d LNs of Batf3^-/-mice possessed higher expression of CD62L and preferentially accumulated in d LNs.Conclusion:In murine model of Th2 response induced by OVA/Papain,lung migratory CD103⁺DC restrained the generation of OVA-specific Th2 memory cells,and the fate decisioin between effector and memory cells were dictated during priming phase.CD103⁺DC promoted CD62L expression in activated CD45.1⁺OT-II cells and their accumulatin in d LNs,and thus augmented generation of Th2 memory cells.