An Alternative Dendritic Cell-Induced Murine Model of Asthma Exhibiting a Robust Th2/Th17-Skewed Response

PURPOSE: Simple and reliable animal models of human diseases contribute to the understanding of disease pathogenesis as well as the development of therapeutic interventions. Although several murine models to mimic human asthma have been established, most of them require anesthesia, resulting in variability among test individuals, and do not mimic asthmatic responses accompanied by T-helper (Th) 17 and neutrophils. As dendritic cells (DCs) are known to play an important role in initiating and maintaining asthmatic inflammation, we developed an asthma model via adoptive transfer of allergen-loaded DCs.METHODS: Ovalbumin (OVA)-loaded bone marrow-derived DCs (BMDCs) (OVA-BMDCs) were injected intravenously 3 times into non-anesthetized C57BL/6 mice after intraperitoneal OVA-sensitization.RESULTS: OVA-BMDC-transferred mice developed severe asthmatic immune responses when compared with mice receiving conventional OVA challenge intranasally. Notably, remarkable increases in systemic immunoglobulin (Ig) E and IgG1 responses, Th2/Th17-associated cytokines (interleukin [IL]-5, IL-13 and IL-17), Th2/Th17-skewed T-cell responses, and cellular components, including eosinophils, neutrophils, and goblet cells, were observed in the lungs of OVA-BMDC-transferred mice. Moreover, the asthmatic immune responses and severity of inflammation were correlated with the number of OVA-BMDCs transferred, indicating that the disease severity and asthma type may be adjusted according to the experimental purpose by this method. Furthermore, this model exhibited less variation among the test individuals than the conventional model. In addition, this DCs-based asthma model was partially resistant to steroid treatment.CONCLUSIONS: A reliable murine model of asthma by intravenous (i.v.) transfer of OVA-BMDCs was successfully established without anesthesia. This model more accurately reflects heterogeneous human asthma, exhibiting a robust Th2/Th17-skewed response and eosinophilic/neutrophilic infiltration with good reproducibility and low variation among individuals. This model will be useful for understanding the pathogenesis of asthma and would serve as an alternative tool for immunological studies on the function of DCs, T-cell responses and new drugs.

Two Distinct Subsets Are Identified from the Peritoneal Myeloid Mononuclear Cells Expressing both CD11c and CD115

To this date, the criteria to distinguish peritoneal macrophages and dendritic cells (DCs) are not clear. Here we delineate the subsets of myeloid mononuclear cells in the mouse peritoneal cavity. Considering phenotypical, functional, and ontogenic features, peritoneal myeloid mononuclear cells are divided into 5 subsets: large peritoneal macrophages (LPMs), small peritoneal macrophages (SPMs), DCs, and 2 MHCII⁺CD11c⁺CD115⁺ subpopulations (i.e., MHCII⁺CD11c⁺CD115⁺CD14⁻CD206⁻ and MHCII⁺CD11c⁺CD115⁺CD14⁺CD206⁺). Among them, 2 subsets of competent Ag presenting cells are demonstrated with distinct functional characteristics, one being DCs and the other being MHCII⁺CD11c⁺CD115⁺CD14⁻CD206⁻ cells. DCs are able to promote fully activated T cells and superior in expanding cytokine producing inflammatory T cells, whereas MHCII⁺CD11c⁺CD115⁺CD14⁻CD206⁻ cells generate partially activated T cells and possess a greater ability to induce Treg under TGF-β and retinoic acid conditions. While the development of DCs and MHCII⁺CD11c⁺CD115⁺CD14⁻CD206⁻ cells are responsive to the treatment of FLT3 ligand and GM-CSF, the number of LPMs, SPMs, and MHCII⁺CD11c⁺CD115⁺CD14⁺CD206⁺ cells are only influenced by the injection of GM-CSF. In addition, the analysis of gene expression profiles among MHCII⁺ peritoneal myeloid mononuclear cells reveals that MHCII⁺CD11c⁺CD115⁺CD14⁺CD206⁺ cells share high similarity with SPMs, whereas MHCII⁺CD11c⁺CD115⁺CD14⁻CD206⁻ cells are related to peritoneal DC2s. Collectively, our study identifies 2 distinct subpopulations of MHCII⁺CD11c⁺CD115⁺ cells, 1) MHCII⁺CD11c⁺CD115⁺CD14⁻CD206⁻ cells closely related to peritoneal DC2s and 2) MHCII⁺CD11c⁺CD115⁺CD14⁺CD206⁺ cells to SPMs.