WESTPORT, Jan 05 (Reuters Health) - Although autoimmune reactions to central nervous system antigens are generally thought to have harmful effects, autoimmune T cells can actually protect injured neurons from the spread of damage, Israeli researchers have now shown.

In the January issue of Nature Medicine, Dr. Gila Moalem and colleagues at the Weizmann Institute of Science in Rehovot, Israel, describe experiments in which rats with a partial crush injury of the optic nerve were treated with injections of activated T cells specific to myelin basic protein, a central nervous system self-antigen.

According to the article, the neurons in the treated animals were protected from secondary degeneration. The treated rats "...retained approximately 300% more retinal ganglion cells with functionally intact axons than did rats injected with activated T cells specific for other antigens."

The researchers found that the injected T cells accumulated at the site of nerve injury. On the basis of electrophysiological studies, the authors speculate that "...a transient reduction in energy requirements, owing to a transient reduction in nerve activity," explains the observed neuroprotective effects.

"Our findings...indicate that the activation of specific autoimmunity in the [central nervous system] might not always be detrimental, but could, under certain circumstances, have a physiological role in protecting the damaged [central nervous system]," the investigators conclude.

In an accompanying News and Views article by Kristine Novak, senior author Dr. Michal Schwartz comments, "We have all been taught that the immune system is designed to be kept out of the [central nervous system]. These results prompt us to consider the possibility that T cell-mediated immune activity against self [central nervous system] components can do good for the immune system as well."