Multiple sclerosis: serum factor producing reversible alterations in bioelectric responses.

Serums obtained from patients during acute exacerbations of multiple sclerosis produce a reversible depression of polysynaptic reflex responses when applied to the isolated spinal cord of the frog. Motoneuron discharges initiated by monosynaptic activation through an axosomatic spinal pathway are much less affected than reflex discharges. The active factor in serum appears to depend on the presence of complement.