TREM2 and neurodegenerative disease: Certain authors [34] posit that microglial cells play a beneficial role in resolving numerous CNS diseases and they argue that microglia become deleterious due to diminished expression of crucial receptors (CD200R, CX3CR1, and TREM2) or to mutations, particularly during instances of aging and neurodegenerative diseases; essentially, this effect occurs in scenarios where microglia deviate from their innate properties and become either tolerogenic or hyperactive [35,36].