Organometric Indicators of Lymphoid Organs in Ratswith Different Models of Alzheimer's Disease

Abstract

B a c k g r o u n d . Alzheimer's disease is a progressive neurodegenerative disorder that affects millions of people worldwide. Increasing evidence suggests that antigens of the central nervous system can interact with lymphocytes and antigen-presenting cells through meningeal lymphatic pathways, indicating that both innate and adaptive immune responses may play a role in the development of neurodegenerative diseases. Thymic involution, a characteristic of aging immune systems, leads to a reduction in naive T lymphocyte production, affecting adaptive immune responses and resulting in compromised immune surveillance. Ineffective immune response triggers neurodegeneration through prolonged activation of immune cells, a key characteristic of the disease. The aim of this study was to comparatively assess the reaction of lymphoid organs in rats with two widely used intervention models of Alzheimer's disease induced by intrahippocampal administration of Aβ1-40 and Aβ25-35. M e t h o d s . Male Wistar rats were used in the experiments, including intact and sham-operated animals as controls. Disease progression was confirmed through feeding behavior, body and organ weight measurements, evaluation of cognitive impairments in the Barnes maze behavioral test, and assessment of dopaminergic neuron loss. Hematological parameters were analyzed at the end of the experiment (day 37), including the relative quantity of lymphocytes. Spearman's correlation analysis was performed between organometric indicators of the thymus and spleen and quantitative changes in circulating lymphocytes in animals with different Alzheimer's disease models. R e s u l t s . In rats with Aβ1-40-induced Alzheimer's disease, an increase in splenic index was observed, indicating moderate splenomegaly. A statistically significant increase in the absolute quantity of lymphocytes with a decrease in their relative quantity and marked monocytosis was recorded. There was a strong negative correlation between splenic index and the quantity of circulating lymphocytes. Animals with Aβ25-35-induced Alzheimer's disease did not show differences in splenic index compared to control groups. C o n c l u s I o n s . The development of Alzheimer's disease is accompanied by changes in the weight indices of lymphatic organs involved in antigen presentation and the generation of adaptive immune responses, as well as in the clearance of antigenic material from the brain. Disruptions in correlation links between quantitative characteristics of circulating lymphocytes and weight indices of primary and secondary lymphoid organs may be associated with disturbances in immunopoiesis and immunogenesis.