Open Access

ARTICLE

Hyperthyroidism-Induced Lymphoid Cell Activation in the Lymph Nodes and Spleen of BALB/c Mice

María Belén Rocco, Clara Requena D’Alessio, Valeria Giselle Sánchez, Horacio Eduardo Romeo, María Laura Barreiro Arcos^*

School of Engineering and Agrarian Sciences, Institute of Biomedical Research (BIOMED-UCA-CONICET), Pontifical Catholic University of Argentina, Av. Alicia Moreau de Justo 1600, Buenos Aires, C1107AAZ, Argentina

* Corresponding Author: María Laura Barreiro Arcos. Email:
# Both authors share senior authorship of this manuscript

BIOCELL 2025, 49(4), 629-646. https://doi.org/10.32604/biocell.2025.062525

Received 20 December 2024; Accepted 27 March 2025; Issue published 30 April 2025

Abstract

Introduction: Hyperthyroidism is known to affect various physiological systems, including the immune system. Thyroid hormones (THs) play a crucial role in regulating immune function, and alterations in THs levels can lead to immune dysregulation. Objective: Currently, we aimed to elucidate the effects of hyperthyroidism on immune function in BALB/c mice, with a focus on anatomical and histological changes in lymphoid organs, the immune response to mitogenic stimulation, mitochondrial dynamics, and reactive oxygen species (ROS) production. Methods: Hyperthyroidism was induced in BALB/c mice by administering thyroxine (T4; 14 mg/L) in their drinking water for 30 days. Thyroid function was assessed by measuring triiodothyronine (T3), T4, and Thyroid-Stimulating Hormone (TSH) levels. Lymphoid organ hyperplasia was evaluated through anatomical dissection. Lymphoid responses were analyzed by subcutaneous inoculation with lipopolysaccharide (LPS), followed by histological analysis of lymphoid follicles and evaluation of the morphometric parameters of lymphoid cells using flow cytometry. In vitro cell proliferation was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Mitochondrial morphology and density were assessed by Transmission Electron Microscopy (TEM). ROS and superoxide anion (O₂⁻) production were measured using 2^′,7^′-dichlorodihydrofluorescein diacetate (DCFH-DA) and Nitroblue Tetrazolium (NBT) assays. Results: Hyperthyroid mice exhibited significantly increased T3 and T4 levels, with decreased TSH levels. Lymphoid organs, including the spleen and lymph nodes, were notably enlarged in hyperthyroid mice, with a corresponding increase in lymphoid cell number. LPS stimulation enhanced the number and size of lymphoid follicles, with hyperthyroid mice showing a greater proliferative response. TEM analysis revealed increased mitochondrial density and changes in mitochondrial structure in hyperthyroid lymphoid cells. ROS and O₂⁻ production were significantly higher in hyperthyroid mice, though no apoptotic activity was detected. Conclusion: Hyperthyroidism leads to significant alterations in immune responses, including enhanced lymphoid organ size, increased proliferation of immune cells, and elevated ROS production. These findings provide new insights into the immunomodulatory effects of thyroid dysfunction and its potential impact on immune system regulation, offering a deeper understanding of THs interactions with immune activation.

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