TLR4⁺group 2 innate lymphoid cells contribute to persistent type 2 immunity in airway diseases

Group 2 innate lymphoid cells (ILC2s) directly contribute to local inflammation in type 2 inflammatory airway diseases. Here, we identify ILC2 subsets by single cell RNA sequencing in chronic rhinosinusitis with nasal polyps (CRSwNP) and in a memory inflammatory mouse model. We find that toll-like receptor 4 (TLR4)⁺ILC2s, with similar markers to their human counterparts, expresse memory cell markers, persist over time, and respond more vigorously to a secondary unrelated antigen challenge in the mouse model. Genetic ablation of TLR4 or blockade by anti-TLR4 antibodies leads to the reduction of IL-13 expression from ILC2s and mucus production in mice. The assay for transposase-accessible chromatin sequencing further confirms the importance of accessible TLR4 gene loci and its down-stream signaling pathway in maintaining trained immunity of TLR4⁺ILC2s after repeated stimulation by HDM. Taken together, TLR4 has a function in trained immunity maintenance within ILC2s, which may contribute to disease chronicity through a non-specific immunological memory.