SMAD4-deficient Dendritic Cells in the Murine Lung shows an Activated Phenotype

Abstract

Abstract SMAD4 is a signaling intermediate that acts downstream of the TGFb receptor. This signaling pathway is known to regulate expression of the Itgae gene (CD103) in activated CD8 T cells. Whether SMAD4 plays a role in induction or maintenance of CD103+ dendritic cells (DCs) has not been investigated. To address this question, we crossed SMAD4 floxed mice with Cre under the control of the CD11c promoter. DCs in the lung, spleen and bone marrow of naïve CD11c-SMAD4 mice were analyzed by multi-parameter flow cytometry. The lungs of Smad4-deficient mice contained smaller numbers of CD11c+ cells than control animals, and the remaining cells expressed costimulatory molecules and CD11b at high levels. Lung suspensions were metal barcoded for time of flight cytometry (cyTOF) and viSNE maps were contracted using 25 parameters. Under these homeostatic conditions, Smad4-abalation caused a dramatic decrease in CD11c+ DCs with activation of pSTAT5, when compared to DCs from littermate controls. Activation of pSTAT5 in KO was specific to CD11c+ DCs as no difference was seen in other cell types including T cells. Our data indicate that the lungs of SMAD4-CD11c KO mice were depleted of migratory DCs, which migrated to the draining lymph nodes after spontaneous maturation. We currently are exploring whether DC-depletion undermines cell mediated immunity to respiratory virus infection.