Phenotypic alterations in peripheral blood B Lymphocytes of patients with Alzheimer's Disease.

Introduction: Dysfunction of humoral immunity has been implicated in the pathogenesis of Alzheimer's disease (AD). The distribution of B lymphocyte subsets and their clinical relevance in AD remain unclear.

Objective: In this study, we aimed to investigate the distribution of peripheral blood B lymphocyte subsets and their relevance with cognition and biomarkers in AD.

Design, setting, and participants: We evaluated the immunophenotype of peripheral B lymphocytes in 27 AD patients confirmed by PET-Amyloid scan and 32 cognitively normal controls.

Results: The phenotype of B lymphocytes is altered in AD patients. AD patients exhibit a decrease in both the numbers and proportions of switched memory (SwM) B cells and double-negative (DN) B cells. The proportion of unswitched memory (USwM) B cells was increased after in vitro stimulation. Additionally, B cells that produce proinflammatory cytokines including GM-CSF, IFN-γ, and TNF-α are increased, while those that produce the anti-inflammatory cytokine IL-10 are decreased in AD patients after in vitro stimulation. These alterations in B cell populations were linked to cognitive functions and biomarkers, including Aβ42/40 and pTau181, in AD patients.

Discussion: This study reveals an altered B-lymphocyte phenotype in AD patients, marked by functional and compositional dysregulation. Further research incorporating mechanistic, longitudinal, and functional studies is needed to determine whether these immune perturbations directly contribute to AD pathogenesis or arise as secondary effects of neurodegeneration.