Immunoglobulin G induces microglial superoxide production.

Activating microglias observed in the white matter after chronic cerebral hypoperfusion may play an important role in white matter changes (WMC). Microglial activation has been considered as a result of neuronal damage, however, recently it came to be recognized as a possible cause of the damage in various neurodegenerative diseases. The protective effect of an immunosuppressant on the WMC suggests that an immunologic reaction participates in the pathogenesis. Using a MCLA-dependent chemiluminescence method, we investigated the effect of immunoglobulin G (IgG) on microglial superoxide production. IgG stimulated microglias to produce superoxide. Microglial superoxide production by the Fab fragment of rat IgG was significantly less than that by the Fc fragment of rat IgG. The protective effect of an immunosuppressant on WMC may use the inhibiting effect on IgG. Our results suggest that if microglias come in contact with IgG in lesions, oxidative stress mediated by superoxide from microglial deteriorates WMC.