Deficiency of IL-10+KLRG1+ ILC2s drives pathogenic B cell responses in myasthenia gravis

Myasthenia gravis (MG) is an autoantibody-mediated disorder of the neuromuscular junction. Although the adaptive immune mechanisms that drive MG are well defined, the contribution of innate immune cells—particularly group 2 innate lymphoid cells (ILC2s), which include a recently recognized IL-10-producing regulatory subset—to the breakdown of B cell tolerance in MG remains unknown. We used multiparameter flow cytometry to profile circulating ILC2s in 15 treatment-naïve, acetylcholine receptor antibody-positive (AChR + ) patients with MG and 15 healthy controls, and integrated single-cell transcriptomes of circulating ILCs from two healthy donors (GSE240441) and three patients with MG. ILC2 subsets were defined transcriptomically and validated phenotypically. The regulatory function of ILC2s was tested in co-cultures of sorted ILC2s with MG patient-derived B cells, with or without interleukin-10 (IL-10) antibody neutralization and recombinant IL-10, and AChR-antibody was quantified by enzyme-linked immunosorbent assay. Circulating ILC2s were reduced in patients with MG ( n = 15) compared with healthy controls ( n = 15) and inversely correlated with disease severity. Single-cell analysis revealed three ILC2 subsets: a proliferative precursor (C0), an IL-10⁺KLRG1⁺ regulatory subset (C1), and a pro-inflammatory subset (C2). Transcriptomic analysis suggested a relative depletion of C1 in MG; exploratory pseudotime analysis suggested a developmental bias away from the regulatory C1 fate toward the pro-inflammatory C2 fate. MG-derived C1 cells additionally showed loss of B cell suppressive transcriptomic signatures. In co-cultures, healthy control–derived ILC2s suppressed the differentiation of patient-derived B cells into long-lived plasma cells and antibody-secreting cells and reduced AChR-antibody production in a dose-dependent manner, whereas MG patient–derived ILC2s showed a trend toward reduced suppressive capacity. The suppressive effects were abolished by IL-10 monoclonal antibody neutralization. Depletion of KLRG1⁺ ILC2s (C1) reduced IL-10 production and abolished suppression, whereas recombinant IL-10 restored it. These results indicate that C1 is the major IL-10-producing subset suppressing autoreactive B cells in MG. We identify deficiency of IL-10 + KLRG1 + ILC2s as an unrecognized innate immune checkpoint that restrains pathogenic B cell responses in MG; its failure licenses autoreactive B cell differentiation and autoantibody production. Restoring this regulatory subset represents a potential therapeutic hypothesis that warrants future investigation.