Absence of natural killer (NK) cell activity against oligodendrocytes in multiple sclerosis

The cytotoxicity of natural killer (NK) cells directed to enriched cultures of bovine oligodendrocytes was investigated in multiple sclerosis (MS) patients and controls. Macrophage-depleted peripheral blood lymphocytes were used as effector cells in a 4-h 51Cr release assay. No significant cytotoxic activity to oligodendrocytes was identified in either MS or control groups. In contrast, a definite cytotoxic activity directed toward K562 cells was observed in the study populations. No statistically significant difference was observed between chronic progressive or stable MS, other neurological diseases (OND), and normal controls. These results indicate that NK cell activity directed toward intact bovine oligodendrocytes is not significantly different between MS and control groups and question the significance of studies employing K562 cells as the target in NK assays in MS. Furthermore, these observations suggest that NK-mediated cytotoxicity against oligodendrocytes is unlikely to be a specific mechanism mediating demyelination in MS.