Alzheimer's disease has long been described as a disorder confined to the brain, but a study published September 8, 2026 in Nature Neuroscience reports that amyloid pathology also disrupts immune cell production in bone marrow, far from the brain itself. The team, led by Miguel Angel Abellanas and colleagues, worked with the 5xFAD mouse model, which is genetically engineered to accumulate amyloid. They found that as amyloid built up over months, blood-forming stem cells in the bone marrow of the skull and long bones declined, and the marrow's output of monocytes, immune cells that can mature into brain-protective macrophages, fell with them. The researchers traced the disruption to circulating type I interferon, an immune signaling molecule, reaching the marrow from outside the brain and impairing the normal maturation of monocytes.
The reduced monocyte supply meant fewer of the patrolling and infiltrating immune cells that other research has linked to lower brain inflammation reached the mouse brains. The team reported that a similar altered pattern in circulating monocytes appeared in blood samples from people with Alzheimer's disease compared with those without the diagnosis, an observational comparison rather than a test of cause. When the researchers blocked the interferon signal in the mice, either with antibodies or by using bone marrow genetically lacking the interferon receptor, monocyte production recovered, more of the cells reached the brain, and the mice showed less memory impairment than untreated 5xFAD mice.
A companion commentary in the same journal issue frames the findings as evidence that the peripheral immune system, not only the brain, may be a target worth studying further in Alzheimer's disease. Type I interferon blocking antibodies already exist and are approved for other conditions such as lupus, but the study did not test any such drug in Alzheimer's patients, and the authors describe the peripheral immune system as a potential therapeutic target for future research, not a treatment.