The discovery may help find a way to reduce stroke damage and improve recovery for people who suffer a stroke.
The Spanish study appears in the Feb. 21 online issue of Stroke.
Researchers took blood samples from 231 people who suffered an ischemic stroke. This kind of stroke is caused by a blood clot that blocks the flow of blood to the brain.
Blood samples were collected within 12 hours of admission to the hospital from 80 percent of the patients and within six hours of admission from 50 percent of the patients.
The researchers measured levels of two natural anti-inflammatory cytokines -- IL-10 and IL-4.
They found patients with low levels of IL-10 in their blood during the first hours after having a stroke were three times more likely to have worsening neurological symptoms.
Here's where you can learn more about stroke.