Mutual effect of cerebral amyloid β and peripheral lymphocytes in cognitively normal older individuals

We hypothesized that cerebral amyloid accumulation is reflected in the periphery in the pre-dementia stage and used flow cytometry to investigate the peripheral lymphocytes as an easily accessible biomarker to observe neuro-inflammation. We aimed to determine whether peripheral lymphocytes are related to the cortical amyloid burden or vice versa in cognitively normal older subjects.

We applied [¹¹ C] Pittsburgh compound B (PiB)-positron emission tomography to 36 cognitively normal older individuals, and Aβ deposition was quantified by cortical binding potential (PiB-BP_ND ). Blood samples were obtained, and lymphocyte subsets were evaluated. We examined differences between low and high PiB-BP_ND groups in the percentage of B cells, T cells, helper T cells, cytotoxic T cells, regulatory T cells, and natural killer cells_. RESULTS: Subjects with high PiB-BP_ND showed significantly higher percentage of cytotoxic T cells (%CD3⁺ ). Correlation analysis revealed a significant relationship between the percentage of cytotoxic T cells and global cortical mean PiB-BP_ND . Hierarchical regression analyses showed that cytotoxic T cells were significantly related to the value of global cortical mean PiB-BP_ND and vice versa.

Our results indicated that a specific peripheral immune response, reflected in the increased ratio of cytotoxic T cells, could be regarded as a preclinical sign of AD and could be attributed to the Aβ neuropathological mechanism. Copyright © 2017 John Wiley & Sons, Ltd.