Next, iMGLs were validated as surrogates of microglia using both functional and physiological assays. To this end, cytokine/chemokine secretion by iMGLs was measured following stimulation by Lipopolysaccharide (LPS), IL-1β or IFNγ. IL-1β and IFNγ are two cytokines that are elevated in AD patients and mouse models (Abbas et al., 2002; Blum-Degen et al., 1995; Patel et al., 2005; Wang et al., 2015) (Figure 3C). Basally, iMGLs secrete 10 of the examined cytokines at low but detectable levels (Table S2). However, in response to IFNγ or IL-1β, iMGLs secrete 8 different chemokines including TNFα, CCL2, CCL4, and CXCL10. As expected, iMGLs robustly responded to LPS with induction of all measured cytokines except for CCL3 (Table S2 for values). Collectively, iMGLs differentially release cytokines/chemokines based on their cell-surface receptor stimuli, a finding that closely aligns with the responses observed in acutely isolated primary microglia (Rustenhoven et al., 2016).
