Flt3-L Increases CD4⁺CD25⁺Foxp3⁺ICOS⁺Cells in the Lungs of Cockroach-Sensitized and -Challenged Mice

Abstract

We previously reported in an ovalbumin-induced model of allergic asthma that Fms-like tyrosine kinase 3 ligand (Flt3-L) reversed airway hyperresponsiveness (AHR) and airway inflammation, and increased the number of regulatory CD11c high CD8a high CD11b low dendritic cells in the lung. In this study, we investigated the effect of Flt3-L in a clinically relevant aeroallergen-induced asthma on the phenotypic expression of lung T cells. Balb/c mice were sensitized and challenged with cockroach antigen (CRA), and AHR to methacholine was established. These mice received three intraperitoneal injections of anti-CD25 antibody (PC61; 250 mg) and Flt3-L (3 mg) daily for 10 days. Cytokines and Ig levels in the serum were measured and differential bronchoalveolar lavage fluid (BALF) cell counts were examined. Flt3-L reversed AHR to methacholine to the control level. Flt3-L significantly decreased levels of BALF IL-5, IFN-g, eosinophilia and substantially increased IL-10 and the number of CD4 1 CD25 1 Forkhead winged helix transcription factor box P3 (Foxp3 1 ) IL-10 1 T cells in the lung. Administration of PC61 antibody blocked the effect of Flt3-L and substantially increased AHR, eosinophilia, and BALF IL-5 and IFN-g levels, and decreased BALF IL-10 levels and the number of CD4 1 CD25 1 Foxp3 1 IL-10 1 T cells. Flt3-L significantly decreased CD62-L, but increased inducible costimulatory molecule and Foxp3 mRNA expression in the CD4 1 CD25 1 T cells isolated from lungs of Flt3-L-treated, CRA-sensitized mice compared to CRA-sensitized mice without Flt3-L treatment and PBS control group. Flt3-L significantly inhibited the effect of CRA sensitization and challenge to increase GATA3 expression in lung CD4 1 CD25 1 T cells. Collectively, these data suggest that the therapeutic effect of Flt3-L is mediated by increased density of naturally occurring CD4 1 CD25 1 Foxp3 1 IL-10 1 ICOS 1 T-regulatory cells in the lung. Flt3-L could be a therapeutic strategy for the management and prevention of allergic asthma.

Fms-Like Tyrosine Kinase 3 Ligand Decreases T Helper Type 17 Cells and Suppressors of Cytokine Signaling Proteins in the Lung of House Dust Mite–Sensitized and –Challenged Mice

“…In addition, we found that ovalbumin-sensitized mice treated with Flt3-L increased the number of regulatory CD11c high CD8a high CD11b low DCs in the lung (42). We also found that administration of Flt3-L significantly increased the number of CD4 1 CD25 1 Foxp3 1 IL-10 1 T cells in the lungs of cockroach-sensitized and -challenged mice (43). Furthermore, adoptive transfer of T-regulatory cells (Tregs) reverses AHR and airway inflammation (45).…”

Fms-Like Tyrosine Kinase 3 Ligand Regulates Migratory Pattern and Antigen Uptake of Lung Dendritic Cell Subsets in a Murine Model of Allergic Airway Inflammation

“…The therapeutic effect of Flt3L is not only limited to the OVAinduced mouse model of allergic airway inflammation, but it has been observed in a clinically relevant cockroach-induced mouse model of asthma (29). Our study helps define the role of Th1 activation in counteracting Th2 response in allergic asthma.…”

Programmed Death-1 Antibody Blocks Therapeutic Effects of T-Regulatory Cells in Cockroach Antigen-Induced Allergic Asthma

“…On Days 28-30 and Day 32, mice received an aerosol challenge of CRA antigen (50 mg/ml). On Day 33, AHR to methacholine was measured according to the established methods in our laboratory (24,25) (Figure 1). …”

“…Mice were mechanically ventilated with Harvard Rodent Ventilator model 683 (Harvard Apparatus, Holliston, MA). Mice were challenged with aerosolized PBS, followed by increasing doses of methacholine (3.1, 6.25, 12.5, 25, 50, and 100 mg/ml) to measure specific airway resistance (24,25).…”

“…We isolated CD4 1 CD25 1 and CD4 1 CD25 2 from the lungs and spleens of BALB/c mice by the method previously reported (24,25). Briefly, tissues were digested using collagenase D (Roche Molecular Systems, Pleasanton, CA) (1 mg/ml) and 5 ml of RPMI-1640 (Cambrex, East Rutherford, NJ), and incubated at 378C in a CO 2 incubator for 90 min.…”