Aβ₄₂ is the predominant form of amyloid β-protein in the brains of short-term survivors of head injury

FATAL head injury results in the formation of diffuse parenchymal deposits of amyloid β-protein (Aβ) in the brains of approximately 30% of individuals. We used carboxyl terminal-specific antisera to examine the exact nature of these deposits in paraffin sections of neocortex from seven head-injured patients. Immunostaining for Aβ₄₂ was observed in all parenchymal deposits whereas staining for Aβ₄₀, the form of the protein which predominates in serum and cerebrospinal fluid, was seen in only a small proportion of deposits. The relative paucity of Aβ₄₀ suggests that post-traumatic deposits do not arise as a result of passive leakage from damaged cerebral blood vessels but are similar to the early Aβ₄₂ parenchymal deposits seen in Down's syndrome and Alzheimer's disease.