As IL-1β was elevated in the hippocampus of female TRAP-exposed rats at 3 months of age, coincident with increased AD pathology (Patten et al., 2021), one possibility is that an increase in M-CSF indicates a response of the immune system to AD pathology and inflammation (Elmore et al., 2014; Dagher et al., 2015; Sasaki, 2016; Unger et al., 2018). Here, CSF1 is linked to Alzheimer disease.