Researchers at the University of California in Los Angeles ( UCLA)said they found that the immune defect makes it difficult to clean the brain of waste products that can form the definitive hallmark of the disease.

In findings published in the Journal of Alzheimer's Disease, researchers said the immune defect may lead to over-saturation of the brain with amyloid-beta, which form amyloid plaques.

It marks the first time researchers have discovered that the innate -- or more primitive -- part of the immune system may play a role in the development of Alzheimer's disease, scientists said.

Could Lead to a New Approach

The findings could lead to a new approach in diagnosing and correcting the immune defect, according to researchers.

Scientists using blood samples found that in healthy people, cells belonging to the innate immune system called macrophages cleared amyloid-beta in a test tube test developed at UCLA, researchers said.

The macrophages of some Alzheimer's patients, however, could not adequately perform the cleaning job.

"Macrophages are the janitors of the innate immune system, gobbling up waste products in the brain and throughout the body," said Milan Fiala, a researcher at UCLA.

May Have a Role in Other Diseases

The immune defect also may have a role in other diseases involving a build-up of waste and plaques, such as in cardiovascular disease and Gaucher's disease, he said.

"If further study shows that this defective macrophage function is present in most Alzheimer's disease patients, new hormonal or immune-boosting approaches may offer new approaches to treating the disease," Fiala said.