Loss of lysosomal neutral proteinase from leucocytes induced by the action of multiple sclerosis-specific brain antigens.

Lysosomal neutral proteinase levels were assayed in leukocytes of patients with other neurological diseases before and after the reaction with MS-specific brain antigens (MSG2). The lysosomal neutral proteinase activity of MS leucocytes was found to be higher than in the two other groups under investigation. To assay the effect of MSG2, 1 x 10(6) leucocytes were incubated with 500 ng of protein MSG2 and with 500 ng of protein of a corresponding fraction from control brain (KG2). Intracellular levels of lysosomal neutral proteinase in leucocytes of all the subjects studied were found to be lowered by the action of both MSG2 and KG2. However, loss of intracellular neutral proteinase induced by the action of MSG2 on all leucocytes was significantly higher than that by KG2 (P less than 0 . 0025). It is suggested that macrophages (monocytes) were stimulated to increased lysosomal enzyme activity, initiated by stimulation of T lymphocytes caused by MS-specific brain antigens.