Group 2 innate lymphoid cells are a non-redundant source of interleukin-5 required for development and function of murine B1 cells.

Tissue-resident immune cells, such as innate lymphoid cells, mediate protective or detrimental immune responses at barrier surfaces. Upon activation by stromal or epithelial cell-derived alarmins, group 2 innate lymphoid cells (ILC2s) are a rapid source of type 2 cytokines, such as IL-5. However, due to the overlap in effector functions, it remains unresolved whether ILC2s are an essential component of the type 2 response or whether their function can be compensated by other cells, such as T cells.

Fungal symbiont transmitted by free-living mice promotes type 2 immunity.

The gut mycobiota is crucial for intestinal homeostasis and immune function. Yet its variability and inconsistent fungal colonization of laboratory mice hinders the study of the evolutionary and immune processes that underpin commensalism. Here, we show that Kazachstania pintolopesii is a fungal commensal in wild urban and rural mice, with an exceptional ability to colonize the mouse gastrointestinal tract and dominate the gut mycobiome.