Alzheimer's: a deficit of activity of the immune cells can explain the appearance of the disease

US researchers have discovered that immune cells in the brain can, when weakened, be the cause of Alzheimer's disease.

Alzheimer's disease remains mysterious. Researchers at the University of Washington Medical School have come up with an important discovery in understanding this pathology. If the brain's immune cells, called microglia, are weakened, Tau protein and amyloid plaques develop, which we know is the cause of the disease. Stimulating these cells would stop or even prevent the progression of the disease.

The role of Tau protein and amyloid plaques

Before the first symptoms, Alzheimer's disease is expressed in the brain through the accumulation of amyloid plaques and the transformation of Tau protein. Gradually, it causes the degeneration of neurons and the loss of cognitive functions characteristic of the disease. For a long time scientists have been wondering about the links between this protein and amyloid plaques.

Impaired cells that create an environment conducive to disease

In this new research, originally published in Nature Neuroscience, the researchers conducted a study on mice. They first started from the observation that a mutation in the TREM2 gene weakened microglia and therefore used it to create several groups of rodents: one with normal microglia and the other with weakened microglia. Then they injected small amounts of Tau proteins into the brains of the mice. Those with weakened microglia had more deformed structures of the Tau protein near the amyloid plaques.

These are present in the brains of many older people and do not always cause Alzheimer's. But when the immune cells of the brain are weakened, the amyloid plaques damage the surrounding neurons and create a favorable environment for the deformation of the Tau structures.

Microglia, cause and cure of the disease

Other tests have shown that the immune cells of the brain, when they function normally, isolate these plaques and prevent them from attacking the neurons. For researchers, it would be possible to use microglia to prevent the evolution of the disease: when these immune cells are boosted, it could slow down the deformation of Tau protein structures and thus cognitive losses. Scientists are already working on drugs that stimulate these cells and prevent the development of the disease.

Today incurable, Alzheimer's disease results from a slow degeneration of neurons, beginning at the level of the hippocampus (a brain structure essential for memory) and extending to the rest of the brain. It is characterized by recent memory disorders, executive functions and orientation in time and space. The patient progressively loses cognitive abilities and autonomy. 900,000 people are affected in France, according to Inserm, figures are constantly increasing.