BDNF and Cognitive impairment: Immune retraining or tolerance induction through peripheral inflammatory stimuli can exacerbate or mitigate Alzheimer disease pathologic factors.48 Preclinical studies of BCG vaccine in an Alzheimer disease mouse model found reduced cognitive deficits accompanied by markedly high CD45, interleukin-10–secreting monocyte infiltration into choroid plexus and perivascular spaces along with anti-inflammatory shifts in brain-derived cytokine levels and increased brain-derived neurotrophic factor,49 greater neuronal dendritic complexity, and higher postsynaptic density-related protein levels.50