SEMA4D and Alzheimer disease: Considering that expression of SEMA4D is upregulated in disease along with reactive astrocytes, which have been reported to contribute to disease progression of both HD and AD, as well as our previously reported therapeutic activity of a SEMA4D blocking antibody to ameliorate neurodegenerative processes in a KI mouse model of HD [41], we sought to determine if SEMA4D blockade can also modulate behavior and neuropathology in an AD transgenic model.