Multiple sclerosis: serum gamma globulin and demyelination in organ culture.

Multiple sclerosis (MS) sera frequently demyelinate organotypic central nervous system (CNS) tissue cultures. To elucidate the possible role of gamma globulins in this form of experimental demyelination we depleted MS sera of all gamma globulins by immunoabsorption and then compared their demyelinating activity with that of the unabsorbed sera. In only 2 out of 16 patients was some demyelinating activity detected in the gamma globulin fraction. In all patients, most of the demyelinating activity was not associated with gamma globulins. In gel filtration experiments, this non-gamma globulin activity was detected in a high-molecular-weight and in a low-molecular-weight fraction.