Healthy and Patient Type 2 Innate Lymphoid Cells are Differently Affected by in vitro Culture Conditions

Abstract

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-Kit high and c-Kit low 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.

Immune Checkpoints and Innate Lymphoid Cells—New Avenues for Cancer Immunotherapy

“…Approximatively 20–40% of lung ILC2 express PD-1, a proportion that is further increased upon influenza infection or papain challenge [ 162 ]. We, and others, have shown that IL-33 and γc cytokines also induce PD-1 expression [ 44 , 46 , 170 , 179 , 180 ]. PD-1 is mainly expressed by KLRG1 + ILC2 [ 170 ] and negatively regulates ILC2 proliferation and cytokine expression [ 44 , 46 , 124 , 163 , 170 , 178 , 179 , 181 , 214 ] ( Figure 2 ).…”

“…In accordance, ILC2 in bronchiolar alveolar lavage samples obtained after allergen challenge increased CD137 expression compared to blood ILC2 [ 190 ]. However, in another study, no changes in CD137 expression were found on in vitro stimulated ILC2 despite multiple culture conditions from both healthy donors or allergic patients [ 180 ]. While additional studies are warranted, evidence to date predominantly supports that tissue resident ILC2 may express CD137; yet the conditions of when and how CD137 is induced on ILC2, as well as how these impact various disease processes, remain unknown.…”

Interleukin‐33 increases type 2 innate lymphoid cell count and their activation in eosinophilic asthma

“…Patients with EA exhibit worse symptoms than those with non‐EA (non‐eosinophilic asthma (NEA)), regardless of asthma severity 1 . Recent studies have confirmed the crucial involvement of innate lymphoid cells (ILC2s), a rare group of lymphocytes, in innate immune responses to allergic diseases 2 …”

“…1 Recent studies have confirmed the crucial involvement of innate lymphoid cells (ILC2s), a rare group of lymphocytes, in innate immune responses to allergic diseases. 2 Innate lymphoid cells lack antigen recognition receptors and produce IL-13 and IL-5, both of which are involved in EA pathogenesis. 3 Interleukin-33, which is produced by bronchial epithelial cells, is crucial for the activation of resident lung Th2 cells as well as ILC2s to produce IL-5, resulting in the development of chitin-induced airway eosinophilia.…”

“… 1 Recent studies have confirmed the crucial involvement of innate lymphoid cells (ILC2s), a rare group of lymphocytes, in innate immune responses to allergic diseases. 2 …”