An extensive new study has identified a specific fault in the immune system of people with Alzheimer’s disease, pointing to a previously underexplored avenue for understanding – and potentially treating – the condition.
Researchers used a “systems immunology” approach to analyse blood samples from 184 people with Alzheimer’s disease and 105 of their healthy spouses. They found a clear disturbance in the way B cells – the immune cells that help make antibodies – mature. This defect was strongly linked not only to having Alzheimer’s, but also to how severe a person’s cognitive decline was.
Crucially, the team showed that this abnormal B cell maturation was not explained by age, infections, or shared environment, suggesting it is an intrinsic feature of the disease rather than a side effect of ageing or exposure to particular viruses.
Looking at the immune system as a whole
Alzheimer’s disease is usually discussed in terms of amyloid plaques and tau tangles in the brain. Still, a growing body of evidence points to an important role for the immune system and inflammation in driving the disease.
In this study, the researchers took a broad, data-driven view of immunity. They collected peripheral blood mononuclear cells (PBMCs) from patients and controls and used high-dimensional flow cytometry to map out hundreds of distinct immune cell types and subtypes, including:
B cell subsets
CD4 and CD8 T cell populations
Monocytes, NK cells and NKT cells
Cytokine-producing cells after stimulation
In total, they quantified 761 immune variables (cell population frequencies), cleaned and transformed the data, and then used statistical modelling and machine learning to identify which immune features best distinguished Alzheimer’s patients from healthy individuals.
A discrete immune “signature” of Alzheimer’s
When they compared patients and controls, the researchers found that:
Multiple immune cell subsets, including B cells, T cells, monocytes, NK and NKT cells, were associated with disease status.
However, the overall immune profile of Alzheimer’s patients still fell within the broad range of normal seen in healthy people.
This means Alzheimer’s doesn’t appear to cause a global collapse of the immune system. Instead, it produces a discrete, specific pattern of immune changes – an “immunological signature” that only becomes obvious when you focus on the most informative cell types.
Using multivariable logistic regression, they found that just four immune parameters were sufficient to distinguish patients from controls, with an ROC AUC of 0.71. Three of these four top markers were directly related to B-cell maturation.
Defective B-cell maturation – and worse cognition
The most striking finding centred on transitional and immature B cells, which represent early stages in the development of B cells from the bone marrow into fully mature, naïve B cells circulating in the blood.
Compared to their healthy spouses, people with Alzheimer’s had:
A lower proportion of immature B cells within the naïve B cell pool
A reduction in transitional B cells (CD24^high^CD38^high^)
A specific drop in CD10^high^CD21^low^ immature transitional B cells, a key precursor population
Taken together, these patterns suggest a “bottleneck” or suboptimal pipeline in B cell development – fewer early-stage cells successfully maturing into the naïve B cell pool.
Importantly, this B-cell maturation defect was linked to cognitive performance. Patients with the most severe mental impairment (lowest Mini-Mental State Examination scores) had the lowest levels of immature transitional B cells, with a stepwise increase in these cells among those with milder symptoms, up to levels seen in healthy controls.
The study also noted other immune changes, such as:
A decrease in T-bet+ CD8 effector memory T cells
Shifts in CD4 T cell memory subsets and PD-1+ Th2 cells
A slight reduction in non-classical monocytes
But the B cell maturation pathway consistently emerged as the strongest and most reproducible discriminator between Alzheimer’s and healthy individuals, both in traditional statistical models and in random forest machine learning analyses (which achieved an AUC of up to 0.85 using 28 top features).
Not just ageing, infections, or shared lifestyle
Because B-cell output naturally declines with age, the team tested whether they were detecting an age-related effect. Several lines of evidence argued against this:
The Alzheimer’s and control groups were closely age-matched (average ~70 years).
When the researchers formally tested the relationship between age and the key immune parameters, very few showed any association with age, in either patients or controls.
The Alzheimer 's-related B cell maturation defect was seen across the whole age range studied.
They then examined environmental exposures, especially to viruses linked to Alzheimer’s risk, such as Epstein–Barr virus (EBV) and cytomegalovirus (CMV). Seropositivity for EBV and CMV was similar across groups, and restricting the analysis to EBV- or CMV-positive individuals did not alter the disease-associated immune patterns.
Finally, by comparing each patient’s immune profile with that of their spouse, the team could estimate how much shared environment shapes immunity. While spouses generally show more similar immune profiles than randomly paired individuals, this spousal concordance disappeared when the analysis was restricted to the immune parameters associated with Alzheimer’s.
Together, these results strongly suggest that the B cell maturation defect and related immune changes are disease-intrinsic, rather than by-products of ageing, infections, or a shared lifestyle.
What this means for Alzheimer’s research and treatment
This work adds a new dimension to our understanding of Alzheimer’s disease:
It provides robust evidence that specific aspects of the adaptive immune system, particularly B-cell development, are altered in Alzheimer’s disease.
It identifies blood-based immune signatures that correlate with disease presence and cognitive decline, potentially useful for future biomarker development.
It highlights B-cell maturation pathways as a promising target for mechanistic studies and perhaps, eventually, therapeutic modulation.
The authors note that their findings should now be validated in independent cohorts, and that further research is needed to understand precisely how impaired B cell maturation might contribute to brain pathology – for example, through altered antibody production, impaired immune surveillance, or disrupted crosstalk with microglia and other brain-resident immune cells.
Still, the message is clear: Alzheimer’s is not just a brain disease – it’s also an immune disease. Understanding the immune side of the story may open new avenues for detecting, tracking, and ultimately treating this devastating condition.
Read the article here: https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.70952