The origin and nature of the complex autoantibody profile in cerebrospinal fluid.

The present study demonstrates, using human protein microarrays and plasma and cerebrospinal fluid samples obtained pre-surgically and simultaneously from 46 hip fracture repair patients, that CSF exhibits an extraordinarily complex IgG autoantibody profile composed of thousands of autoantibodies. We show that the pattern of expression levels of individual autoantibodies in CSF closely mimics that in the blood, regardless of age, gender or the presence or absence of disease, indicative of a blood-based origin for CSF autoantibodies. In addition, using five longitudinal serum samples obtained from one healthy individual over a span of nine years, we found that blood autoantibody profiles are remarkably stable over a long period of time, and that autoantibody profiles in both blood and CSF show features that are common among different individuals as well as individual-specific. Lastly, we demonstrate that an elevated CSF/plasma autoantibody ratio is more common in elderly hip fracture repair patients that experienced post-operative delirium than in non-delirium subjects, thus highlighting the crucial role that blood-brain and/or blood-CSF barrier compromise may play in the development of post-operative delirium.