Ecto-5'nucleotidase activity in B and T lymphocytes and monocytes of patients with multiple sclerosis.

Ecto-5'nucleotidase activity in the plasma membrane of B and T lymphocytes and cultured and noncultured monocytes from patients with multiple sclerosis and from age- and sex-matched control subjects was determined by radioisotopic assay. The activity on lymphocytes and noncultured monocytes was normal, but the activity on cultured monocytes was found to be higher than normal in 70% of patients with active disease and lower than normal in 85% of patients with chronic inactive disease. Immunofluorescence staining with monoclonal antibodies, carried out in parallel with each assay, did not show any phenotypic differences between each cell population and its control.