Elevated levels of the complement components C3 and factor B in ventricular cerebrospinal fluid of patients with traumatic brain injury.

Immunological events occurring in the central nervous system (CNS) as a result of head trauma are largely unexplored. We report here that the levels of the alternative pathway complement proteins C3 and factor B are elevated in the cerebrospinal fluid (CSF) of head-injured patients. C3 and factor B indices suggest that changes in C3 and factor B levels in CSF are most likely due to altered blood-brain barrier integrity and not to intrathecal synthesis. These data demonstrate, for the first time, elevated levels of complement proteins in CSF of patients with severe traumatic brain injury. Elevated complement levels in brain injury may contribute to secondary damage.