TREM2 and neurodegenerative disease: Additionally, studies have shown that TREM2 expression is upregulated upon inflammatory insult and/or neurodegenerative disease, including Parkinson’s disease (PD) (Liu et al., 2016), amyotrophic lateral sclerosis (ALS) (Cady et al., 2014), stroke (Kawabori et al., 2015), traumatic brain injury (Saber et al., 2017), and AD (Lue et al., 2015).