S100B and Alzheimer disease: Thus, in the context of cross-reactivity between AßP-42 antibodies, BBB proteins such as S100B, AQP4, claudin-5, and GFAP, and many other brain-associated antigens, BBB compromise may be an important risk factor in the intraneuronal deposition of AßP-42 and in the initiation and/or progression of neurodegenerative diseases, including AD.