CX3CR1 and Alzheimer disease: To investigate the effect of partial CX3CR1 deficiency on progression of AD, we used bigenic mice expressing mutation of presenilin 1 and the amyloid precursor protein with the Swedish mutation (PS1-APP) (18, 19), and analyzed Alzheimer's-like pathology in PS1-APP mice heterozygous for CX3CR1 (PS1-APP-CX3CR1+/−).