Scientists have reversed the damage caused to the brain by Alzheimer's disease during tests on mice.
People with Alzheimer's have a build up of abeta deposits in the brain
The US team used an antibody to remove the build up of potentially damaging deposits from the area of the brain responsible for memory and cognition.
The treatment reversed the nerve cell damage in days, Washington University School of Medicine researchers said.
UK experts described the findings, published in the Journal of Clinical Investigation, as "exciting".
Prior to the study, it was thought that once the damage had been caused to the brain there was no way of repairing it.
Lead author Robert Brendza said: "We thought that clearing the plaques (deposits) would halt the progression of the damage.
"But what we saw was much more striking - in just three days there were 20 to 25% reductions in the number or six of the existing swellings."
He said more research was needed to see if the effects could be repeated in humans with the degenerative brain disorder for which there is no cure.
It is estimated that 2% to 5% of people over 65 years of age and up to 20% of those over 85 years of age have Alzheimer's.
The cause of the disease is not known although people with Alzheimer's do have a build up of abeta, a glycoprotein, which could be responsible for the nerve cell damage.
Mice with a build up of abeta were injected with the antibody and then using a dye to give detailed images of the nerve cell branches, the team were able to monitor the improvement over a few days.
"From the details that I've seen, these could be very interesting results.
Alzheimer's Research Trust deputy chief executive Harriet Millward said: "This new work is particularly interesting since it seems the nerve cells that were damaged in Alzheimer's disease were able to partly recover after the plaques cleared."
But she added: "We are still a long way from finding an answer to Alzheimer's, but by learning more about the disease process, we will be able to accelerate progress towards ways to treat and prevent this devastating condition."
Dr Susanne Sorensen, head of research at the Alzheimer's Society, said several researchers across the world were also looking into the use of antibodies.
But she added: "The research in animal models reported here is exciting because it provides additional, important information about how abeta antibodies may reverse the signs of disease in neurons.
"However, there is still a lot to learn about what happens to the brain cells during Alzheimer's, and what these antibodies do to reverse the situation."