Group 3 innate lymphoid cell-derived CSF2 tunes homeostasis of tissue macrophages and neutrophils.

Group 3 innate lymphoid cells (ILC3) are tissue-resident lymphocytes that contribute to tissue and immune homeostasis. Alterations in ILC3 development or deficiency in their effector functions have beneficial and detrimental outcomes on chronic inflammation, host defense and barrier integrity. Although research has progressed in understanding these cells, multiple aspects of their biology remain poorly understood and difficult to investigate using current available techniques. This is primarily due to the lack of accessible and suitable tools to isolate, manipulate, and investigate ILC3 in vitro and in vivo. Here, we report an economical system to investigate the biology of ILC3 in vitro and in vivo, using the previously described ILC3 cell line MNK3. We demonstrate that MNK3 cells are a relevant model for in vivo investigations into the biology of ILC3. We describe and validate a straightforward strategy to genetically modify MNK3 cells ex vivo to dissect the role of their effector functions in the steady state or during inflammation and infection. Using this system, we identified a previously underappreciated role for ILC3-derived Colony Stimulating Factor 2 (CSF2) in regulating splenic and hepatic myeloid cell homeostasis. Collectively, we present a system to investigate the biology of ILC3 that is suitable, and accessible to a wider audience in academic research.