We found that along the progressive stages of disease pathology, the CP of AD-Tg mice, compared with age-matched wild-type (WT) controls, expressed significantly lower levels of leukocyte homing and trafficking determinants, including intercellular adhesion molecule 1 (icam1), vascular cell adhesion molecule 1 (vcam1), C-X-C motif chemokine 10 (cxcl10) and chemokine C-C motif ligand 2 (ccl2) (Fig. 1a), shown to be upregulated by the CP in response to acute CNS damage and needed for transepithelial migration of leukocytes17, 18, 19. This evidence concerns the gene CCL2 and Alzheimer disease.