Effects of myeloid and plasmacytoid dendritic cells on ILC2s in patients with allergic rhinitis

Background: Group 2 innate lymphoid cells (ILC2s) were reported to serve a critical role in allergic diseases. Myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) play significant roles in allergic immune response. However, effects of DCs on ILC2s in allergic diseases, especially for patients with allergic rhinitis (AR), remain unclear.

Objective: We sought to address the roles of mDCs and pDCs in regulating ILC2 function in AR.

Methods: mDCs and pDCs were cocultured with human PBMCs isolated from patients with AR or ILC2s to measure soluble or intracellular T_H2 cytokines, transcription factors, signaling pathways in ILC2s, and the following mechanisms were further investigated. The levels of peripheral IL-33⁺mDCs, pDCs, and ILC2s were studied in patients under an inhaled allergen challenge.

Results: We confirmed the presence of ILC2s, mDCs, and pDCs in the nasal mucosa of patients with AR. Both allogenic and autologous mDCs were found to activate ILC2s from patients with AR to produce T_H2 cytokines, and increase the levels of GATA-3 and signal transducer and activator of transcription signaling pathways, in which IL-33-producing mDCs exerted the major role by binding on ST2 on ILC2s. We further identified high levels of IL-33⁺mDCs and ILC2s in patients with AR under antigen challenge. Activated pDCs inhibited the cytokine production of ILC2s isolated from patients with AR by secretion of IL-6.

Conclusions: mDCs promote ILC2 function by the IL-33/ST2 pathway, and activation of pDCs suppresses ILC2 function through IL-6 in patients with AR. Our findings provide new understanding of the interplay between DCs and ILC2s in allergic diseases.