Flt-3 Ligand (FL) Treatment Upregulates PDL2 and Downregulates CCR7 in Distinct Myeloid Dendritic Cell (DC) Populations in the Lungs of Asthmatic Mice

Abstract

RationaleWe observed that Flt-3 ligand reversed airway hyperresponsiveness (AHR) in a mouse model of asthma. FL preferentially affects the development and differentiation of myeloid DCs. In this study, we examined the phenotype of lung myeloid dendritic cells and their responses to ovalbumin (OVA) sensitization and FL treatment.MethodsA mouse model of asthma was established by administration of OVA and confirmed by AHR to methacholine. Sensitized and challenged mice were given either recombinant human FL or PBS. Non-sensitized mice received PBS as controls. CD11c+ lung DCs sorted by MACS were further labeled with CD11c, CD11b, CD8, PDL1, PDL2, and CCR7 antibodies conjugated with fluorochrome. FACS was used to identify phenotypic myeloid DC populations. The expression levels of cell surface markers were analyzed using flow cytometry.ResultsThree distinct lung myeloid DC populations, CD11c+CD11blow, CD11chiCD11bint, and CD11c+CD11bhi were identified. CD11chiCD11bint cells accounted for the majority of the lung myeloid DCs in non-sensitized condition. OVA sensitization significantly increased the proportion of CD11c+CD11bhi cells and decreased CD11chiCD11bint cells but FL treatment reversed the trend. CD11chiCD11bint cells had a higher expression of CD8, PDL1, and PDL2 as compared to CD11c+CD11bhi cells. CCR7 expression was higher in CD11c+CD11bhi cells. PDL2 was upregulated after sensitization and was further unregulated after FL treatment in CD11chiCD11bint cell population. CCR7 was upregulated after sensitization and downregulated after FL treatment in CD11c+CD11bhi cells.ConclusionsCD11chiCD11bint and CD11chiCD11bint DCs may be responsible for immune tolerance and immune response, respectively. FL reverses AHR in asthmatic mice possibly through upregulating PDL2 and downregulating CCR7 on DCs. RationaleWe observed that Flt-3 ligand reversed airway hyperresponsiveness (AHR) in a mouse model of asthma. FL preferentially affects the development and differentiation of myeloid DCs. In this study, we examined the phenotype of lung myeloid dendritic cells and their responses to ovalbumin (OVA) sensitization and FL treatment. We observed that Flt-3 ligand reversed airway hyperresponsiveness (AHR) in a mouse model of asthma. FL preferentially affects the development and differentiation of myeloid DCs. In this study, we examined the phenotype of lung myeloid dendritic cells and their responses to ovalbumin (OVA) sensitization and FL treatment. MethodsA mouse model of asthma was established by administration of OVA and confirmed by AHR to methacholine. Sensitized and challenged mice were given either recombinant human FL or PBS. Non-sensitized mice received PBS as controls. CD11c+ lung DCs sorted by MACS were further labeled with CD11c, CD11b, CD8, PDL1, PDL2, and CCR7 antibodies conjugated with fluorochrome. FACS was used to identify phenotypic myeloid DC populations. The expression levels of cell surface markers were analyzed using flow cytometry. A mouse model of asthma was established by administration of OVA and confirmed by AHR to methacholine. Sensitized and challenged mice were given either recombinant human FL or PBS. Non-sensitized mice received PBS as controls. CD11c+ lung DCs sorted by MACS were further labeled with CD11c, CD11b, CD8, PDL1, PDL2, and CCR7 antibodies conjugated with fluorochrome. FACS was used to identify phenotypic myeloid DC populations. The expression levels of cell surface markers were analyzed using flow cytometry. ResultsThree distinct lung myeloid DC populations, CD11c+CD11blow, CD11chiCD11bint, and CD11c+CD11bhi were identified. CD11chiCD11bint cells accounted for the majority of the lung myeloid DCs in non-sensitized condition. OVA sensitization significantly increased the proportion of CD11c+CD11bhi cells and decreased CD11chiCD11bint cells but FL treatment reversed the trend. CD11chiCD11bint cells had a higher expression of CD8, PDL1, and PDL2 as compared to CD11c+CD11bhi cells. CCR7 expression was higher in CD11c+CD11bhi cells. PDL2 was upregulated after sensitization and was further unregulated after FL treatment in CD11chiCD11bint cell population. CCR7 was upregulated after sensitization and downregulated after FL treatment in CD11c+CD11bhi cells. Three distinct lung myeloid DC populations, CD11c+CD11blow, CD11chiCD11bint, and CD11c+CD11bhi were identified. CD11chiCD11bint cells accounted for the majority of the lung myeloid DCs in non-sensitized condition. OVA sensitization significantly increased the proportion of CD11c+CD11bhi cells and decreased CD11chiCD11bint cells but FL treatment reversed the trend. CD11chiCD11bint cells had a higher expression of CD8, PDL1, and PDL2 as compared to CD11c+CD11bhi cells. CCR7 expression was higher in CD11c+CD11bhi cells. PDL2 was upregulated after sensitization and was further unregulated after FL treatment in CD11chiCD11bint cell population. CCR7 was upregulated after sensitization and downregulated after FL treatment in CD11c+CD11bhi cells. ConclusionsCD11chiCD11bint and CD11chiCD11bint DCs may be responsible for immune tolerance and immune response, respectively. FL reverses AHR in asthmatic mice possibly through upregulating PDL2 and downregulating CCR7 on DCs. CD11chiCD11bint and CD11chiCD11bint DCs may be responsible for immune tolerance and immune response, respectively. FL reverses AHR in asthmatic mice possibly through upregulating PDL2 and downregulating CCR7 on DCs.