1. In the presence of a source of complement, the gamma 2 globulin fraction of rabbit EAE serum results in complete demyelination of myelinated cultures of rat cerebellum. Exposure of the serum to homologous or heterologous brain specifically removes the myelinotoxic activity whereas exposure to non-nervous tissue does not. Polylysine has no effect upon the cultures or upon the demyelinative potency of EAE, whereas heparin inhibits activity presumably through an effect on complement.
2. With the fluorescent antibody technique, the EAE globulins are specifically localized to the myelin sheaths and glial cell membranes during the process of demyelination. As demyelination proceeds, the globulins become localized within the neuroglia in a homogeneous manner which contrasts sharply with the punctate pattern observed in control experiments.
3. The "delayed sensitivity" and classical antibody interpretations of experimental allergic encephalomyelitis are discussed. It is suggested that several factors may be responsible for the pathogenesis of EAE, one of which may well be a myelinotoxic antibody.