Recent studies have implicated the possible pathogenic roles of astrocytes in AD: inflammatory complement proteins C1q, C3d and C4b in astrocyte-derived exosomes are elevated in AD patients (Goetzl et al., 2018), and plasma astrocyte-derived exosome levels of these complement proteins may be used for prediction of MCI to AD conversion (Winston et al., 2019). The gene discussed is C4B; the disease is Alzheimer disease.