Proteolipid protein antiserum does not affect CNS myelin in rat spinal cord culture

Sera from 3 rabbits and 1 goat which contained precipitating antibodies to highly purified rat CNS myelin proteolipid protein (PLP) did not inhibit CNS myelin formation nor destroy intact CNS myelin in cultures of rat spinal cord. CNS myelin which formed in the presence of antiPLP serum and complement appears ultrastructurally identical to myelin formed in normal control cultures. The lack of demyelinating and myelin formation inhibiting activities in antisera to PLP suggests either: (1) PLP is not exposed on the external surface of the myelin membrane; or (2) the externally exposed portions of PLP were rendered nonantigenic during the purification of PLP.