Spinal fluid differences in experimental allergic encephalomyelitis and multiple sclerosis.

The spinal fluid of sheep with experimental allergic encephalomyelitis contains myelin basic protein (6 to 18 nanograms per milliliter) bound to antibody as well as excess free antibody. This bound myelin basic protein appeared concurrently with the onset of the disease and remained elevated until death. In contrast, in active multiple sclerosis, the spinal fluid contains free myelin basic protein and there are no detectable levels of antibody. The results indicate that the antibodies enter the spinal fluid from the serum by passive diffusion. This mechanism may also explain the presence of viral antibodies in the spinal fluid of multiple sclerosis patients.