IL3 and Alzheimer disease: To systematically determine the complex roles of IL-3 on AD pathogenesis and its specific interactions with microglial activity in the participants who had preclinical or clinical AD, we aimed to ascertain the interrelationships between CSF IL-3, microglial activation markers (as reflected by soluble triggering receptor expressed on myeloid cells 2 [sTREM2]), AD pathology, and cognitive change, and to explore effects of CSF IL-3 and CSF sTREM2 on AD pathology and cognitive change using a mediation model.