New York, March 15 (IANS): Stroke is the fourth-leading killer in the world and an important cause of permanent disability.

This may no longer be the same as scientists have now found that using a compound to block the body's immune response reduces chances of disability after a stroke significantly.

The study shows that after a stroke, the injured brain cells provoke the particular immune cells 'CD4 ' T-cells to produce a substance, 'IL-21', that kills the neurons in the blood-deprived tissue of the brain.

For the study, normal mice, ordinarily killed or disabled by an ischemic stroke, were given a shot of a compound that blocks the action of 'IL-21'.

Brain scans and brain sections showed that the treated mice suffered little or no stroke damage.

"This is very exciting because we haven't had a new drug for stroke in decades, and this suggests a target for such a drug," said Zsuzsanna Fabry, a professor of pathology and laboratory medicine at University of Wisconsin School of Medicine and Public Health.

The final part of the study looked at brain tissue from people who had died following ischemic strokes, said Matyas Sandor, professor of pathology and laboratory medicine at the University of Wisconsin.

It found that 'CD4 ' T-cells and their protein, 'IL-21' are in high concentration in areas of the brain damaged by the stroke.

The similarity suggests that the protein that blocks 'IL-21' could become a treatment for stroke, and would likely be administered at the same time as the current blood-clot dissolving drugs, Sandor said.

The study appeared in the Journal of Experimental Medicine.