IL-5-producing Group 2 innate lymphoid cells promote T cell-independent IgA production in cooperation with eosinophils.

This article focuses on the role of interleukin-5 (IL-5)-producing Group 2 innate lymphoid cells (ILC2s) in T cell-independent (TI) immunoglobulin A (IgA) production and intestinal bacterial homeostasis. Using T cell receptor α-deficient mice, the study demonstrates that IL-5 from ILC2s promotes TI IgA synthesis in the large intestine, partly by supporting eosinophil survival, which in turn enhances IgA secretion by IgA+ B cells. Administration of recombinant IL-33 increased IL-5-producing ILC2s and TI IgA levels, while IL-5 deficiency altered the composition of gut microbiota and reduced IgA-coated bacteria, indicating IL-5’s involvement in maintaining intestinal microbial balance. These findings suggest that IL-5-producing ILC2s, together with eosinophils, contribute to mucosal immunity and the homeostasis of commensal bacteria through TI IgA production.