D21-02 Type 2 Cytokines Tune Regulatory T Cell Control of Allergic Airway Disease

Abstract Rationale FOXP3+ regulatory T cells (Tregs) play an indispensable role in restraining aberrant immune responses, including Th2 cell responses that drive allergic asthma. There is great interest in developing Treg-based therapies for allergic asthma, but the mechanisms whereby Tregs specifically restrain Th2 cells remain poorly defined. Treg suppression of adaptive immune responses requires co-localization with antigen presenting cells (APCs) and effector T cells. CCR4 is a chemokine receptor expressed by both Th2 cells and Tregs and implicated in promoting cell trafficking into non-lymphoid tissues. As CCR4 co-localizes Tregs with Th2 cells, we posited that interrogating CCR4 would reveal novel mechanisms controlling Treg suppression of allergic inflammation. Methods We used a murine model of allergic asthma, RNA-sequencing analysis, and a novel Ccr4 conditional knockout mouse to define the role of the CCR4 system in regulating allergic inflammation. Results By employing single cell RNA-sequencing analysis of lung APCs, we demonstrate that a population of activated, type 2 conventional dendritic cells (cDC2s) are the dominant source of the CCR4 ligands during allergic inflammation. We show that the type 2 cytokines IL-4 and IL-13 directly promote cDC2 activation and CCR4 ligand expression. Using a novel, conditional Ccr4 knockout model, we demonstrate that Tregs require CCR4 to efficiently traffic into the lungs and suppress the expansion of cDC2-CD4+ T cell clusters driving allergic inflammation. Furthermore, using bulk RNA-seq analysis, we show that deletion of CCR4 in Tregs results in reduced expression of Asb2, an E3 ubiquitin ligase that regulates actin cytoskeleton dynamics and cell trafficking. We demonstrate that IL-4 directly induces Asb2 expression in Tregs and promotes Treg trafficking efficiency into the lungs during allergic inflammation. Our results demonstrate cell-extrinsic and cell-intrinsic mechanisms whereby the type 2 cytokines dictate Treg trafficking efficiency and suppression of allergic airway inflammation. Conclusions The type 2 cytokines IL-4 and IL-13 orchestrate allergic inflammation in asthma. Here, we demonstrate that IL-4 and IL-13 also play a critical role in tightly controlling Treg suppression of allergic inflammation. Specifically, we show that IL-4 and IL-13 promote Treg migration to the sites of allergic inflammation by 1) inducing cDC2 activation and expression of the CCR4 ligands and 2) directly stimulating Treg trafficking efficiency. Our work suggests that current therapeutic approaches for allergic asthma, which reduce or block IL-4/IL-13 signaling, also reduce Treg suppression. Our findings have important implications for developing effective Treg-based therapies to durably suppress allergic asthma and other allergic diseases. This abstract is funded by: National Institutes of Health