Surprise for Stroke-Researchers

Apoplectic strokes proceed more harmlessly if certain immune cells are missing from the blood. This previously unknown mechanism was presented by scientists from the University of Würzburg in the "Blood" Journal.

Every other minute a person in Germany suffers a stroke. The blockage of vessels providing the brain with blood is usually the cause. People surviving a stroke may be harmed with severe impairments like speech defects or paralyses. The reason: the brain is damaged due to prolonged insufficient blood supply.

What usually blocks the vessels are clots of blood. Dissolving these plugs or not letting them emerge in the first place is the uppermost goal in treating and preventing strokes.

Therefore, the search for new and better therapies starts at the disease's cause: hemostasis, leading to the clot formation. Then, when the Würzburg scientists made a find in a completely different area, they were even more surprised - T-cells also seem to play a role in strokes, though actually these cells are responsible for defence against pathogenic germs.

T-cells with an adverse effect

What exactly it was the researchers have discovered? Mice lacking T-cells because of a genetic defect suffer from less severe strokes than their normal fellow species. Moreover, they develop less neurological impairments, e.g. paralysis, after the stroke.

Hence, T-cells have a negative effect on the course of strokes. This is what the teams around Guido Stoll, Christoph Kleinschnitz and Heinz Wiendl from the neurological university hospital in cooperation with Bernhard Nieswandt from the Rudolf-Virchow Center for Experimental Biomedicine have demonstrated.

"That T-cells exert such a damaging effect in strokes came complete asa surprise", reports Christoph Kleinschnitz. The negative effect isattributable to two subgroups of immune cells, the so called CD4- and CD8-positive T-helper cells.

But in which way do the T-cells intensify the apoplectic stroke? Two possible mechanisms were ruled out by the Würzburg scientists in their experiments. For one thing, the T-cells do not support the clumping of blood platelets, and therefore neither do they encourage the emergence of thrombuses. "For another thing, they do not aid the process in form of a specific immune reaction either", says Neuro-immunologist Heinz Wiendl. Further studies need to find out how the T-cells exert their negative effect.

New approaches to therapy imaginable

The Würzburg scientists are hoping their work will help improving human stroke therapies. If their findings are transferable to humans, new approaches involving deliberately influencing T-cells might arise. For example, switching off the adverse fraction of T-cells temporarily and thereby moderating the impairments at an early stage of the stroke is imaginable. "Until then, further studies need to be conducted though", says the neurologist Guido Stoll.

Results coming from two Collaborative Research Centers

These results have been worked out in the two Würzburg Collaborative Research Centers 688 and 581. Both are financially supported by the German Research Foundation (DFG). The findings were published on March 9th 2010 in the online issue of "Blood", the American Society of Haematology's journal.

Original Publication:
Christoph Kleinschnitz, Nicholas Schwab, Peter Kraft, Ina Hagedorn, Angela Dreykluft, Tobias Schwarz, Madeleine Austinat, Bernhard Nieswandt, Heinz Wiendl, and Guido Stoll: "Early detrimental T cell effects in experimental cerebral ischemia are neither related to adaptive immunity nor thrombus formation." Blood First Edition Paper
10.1182/blood-2009-10-249078

For further information please contact:
PD Dr. Christoph Kleinschnitz
Phone: +49 931 201-23765
E-Mail: christoph.kleinschnitz@uni-wuerzburg.de