Human peripheral lymphocytes defined by anti-myelin-associated glycoprotein antiserum in healthy individuals and in patients with multiple sclerosis.

We investigated both the association between MAG-positive cells and active natural killer cells stained by anti-Leu-11 and the percentage of MAG-positive cells in patients with multiple sclerosis (MS) by indirect immunofluorescence study. Eighty percent of MAG-positive cells were stained with anti-Leu-11. The percentage of MAG-positive cells of 41 healthy individuals was from 5.1 to 16.1% (8.5 +/- 2.7%). The percentage of Leu-7-positive cells (13.8 +/- 4.9%) was always greater than that of MAG-positive cells. In 5 of 17 samples from 14 patients with MS, the percentage of MAG-positive cells was reduced. This finding was not related to disease activity and was not a pathognomonic feature of MS. The percentage of Leu-7-positive cells in patients with MS was not statistically different from that in healthy individuals; however, 4 patients showed a normal number of Leu-7-positive cells and a reduced number of MAG-positive cells. These studies suggest that MAG-positive cells are closely related to active natural killer cells and that "MAG" is a useful marker of human natural killer cells.