About demyelinating properties of humoral antibodies in experimental allergic encephalomyelitis. In vivo and in vitro studies.

In order to elucidate the role of humoral antibodies in the pathogenesis of myelin lesions in experimental allergic encephalomyelitis (EAE) a combined in vivo and in vitro study was done using rabbits immunized with the purified A1 basic protein. Rabbits injected with whole white matter were used for comparison. Demyelinating activity appeared in the rabbit sera 5 days after injection, as tested in myelinated organotypic tissue cultures. In spite of this no lesions of the myelin preceded the appearance of inflammatory cells in the living animals. In the spinal cord changes in vascular permeability, as revealed by leakage of Evans blue-albumin complex, appeared at the same time as the cells. In contrast to in vitro, the mere presence of circulating antibodies in vivo does not appear to be enough to cause structural changes of the myelin. Possible reasons for this discrepancy are discussed; it is emphasized that the inflammatory changes develope first in areas where the so-called blood-brain barrier to diffusion of proteins is lacking.