Healthy and patient type 2 innate lymphoid cells are differently affected by in vitro culture conditions

Background: Type 2 innate lymphoid cells (ILC2s) have emerged as key players in the development of type 2 driven diseases such as allergy and asthma. Due to their low number in the circulation, in vitro expansion is needed to unravel their mechanisms of action. Purpose: The aim of this study is to assess the impact of different culture conditions and address whether the method of expansion may distinctly affect healthy donor or patient-derived ILC2s. Methods: Here, we described the impact of six different culture conditions on the proliferation, phenotype and function of human ILC2s freshly obtained from healthy donors (healthy ILC2s) and allergic patients (patient ILC2s). Results: We showed that the cytokine cocktail or the PHA induced the highest proliferation of healthy ILC2s and patient ILC2s, respectively. We observed that the stromal cells OP9, used as ILC2 feeders, did not boost their proliferation, but impaired the activation marker expression and the function of patient ILC2s. Furthermore, we demonstrated that the culture conditions differently impacted the activation state of c-Kithigh and c-Kitlow ILC2s, in both healthy donors and allergic patients. Last, we also observed that ILC2s expanded only with IL-2 and IL-7 were the most prone to secrete IL-5 and IL-13 upon IL-33 stimulation. In contrast, in patients, the addition of OP9 cells during the expansion restrained their type 2 cytokine secretory functions. Conclusion: This report highlights that culture conditions distinctly impacted on the healthy or patient ILC2 behavior, with important consequences for their study in disease settings.