MMP9 and Alzheimer disease: In line with the trained immunity phenotype in AD, several papers highlighted a signature of trained immunity in atherosclerosis, particularly to various microbial and atherosclerosis-related stimuli in the in vitro system with a macrophage response characterized by elevated levels of TNFα, IL-6, MCP-1, MMP-2 and MMP-9, and increased foam cell formation (92).