The chemokine (C-C motif) ligand 2 (CCL2) protein (also known as macrophage chemoattractant protein 1, or MCP-1) is well-recognized for its ability to mediate macrophage recruitment and migration to sites of inflammation in rheumatoid arthritis, multiple sclerosis, traumatic brain injury, stroke and Alzheimer disease (AD) [1-7]. Here, CCL2 is linked to early-onset autosomal dominant Alzheimer disease.