XCL1 and Alzheimer disease: Our results show that monocytes derived from AD patients over-express Chemokine (C-X-C motif) ligand 1 (CXCL1) that interact with CXC chemokine receptor 2 (CXCR2) in HBMEC to facilitate Aβ-induced transendothelial migration through the endothelial tight junction.