Thymosin α1 Augments CD8⁺ T-Cell Activation and Reverses Exhaustion In Vitro.

Thymosin alpha 1 (Tα1) enhances CD8⁺ T-cell activation and may partially reverse exhaustion in vitro, but further in vivo studies are necessary to confirm these effects.

Summary and findings

This study measured the effects of Thymosin alpha 1 (Tα1) on human CD8⁺ T-cell proliferation, activation, and exhaustion in vitro. The treatment involved Tα1 alone and in combination with CD3/CD28 stimulation. Results indicated enhanced proliferation and activation markers in the combination group compared to individual treatments.

Abstract

<h4>Background</h4>Thymosin alpha 1 (Tα1) is a thymic peptide hormone secreted by the thymus gland with known immunomodulatory properties, yet its specific effects on human CD8⁺ T-cell function remain incompletely understood. This study investigates the influence of Tα1 on CD8⁺ T-cell proliferation, activation, cytokine secretion, and exhaustion status in vitro.<h4>Methods</h4>Human CD8⁺ T-cells were cultured and treated under four conditions: untreated (negative control), CD3/CD28 stimulation (positive control), Tα1 treatment, and combined CD3/CD28 + Tα1 stimulation. Proliferation was measured using carboxyfluorescein succinimidyl ester (CFSE)-based flow cytometry. Surface expression of activation markers (CD69, CD25, HLA-DR) and exhaustion markers (PD-1, TIM-3, LAG-3) was analyzed by flow cytometry. Cytokine secretion (IL-2, IFN-γ, TNF-α, IL-10) was assessed using a multiplex bead-based assay. T-cell exhaustion was induced by repeated CD3/CD28 stimulation before Tα1 treatment.<h4>Results</h4>Tα1 alone moderately increased proliferation and activation of CD8⁺ T-cells, while the combination of Tα1 and CD3/CD28 significantly enhanced the proliferation index and surface expression of CD69, CD25, and HLA-DR compared with individual treatments. Cytokine secretion of IL-2, IFN-γ, TNF-α, and IL-10 was elevated in the combination group, indicating enhanced effector function. In the exhaustion model, CD8⁺ T-cells exhibited overexpression of PD-1, TIM-3, and LAG-3, which was significantly reduced upon Tα1 treatment, suggesting a partial reversal of the exhausted phenotype.<h4>Conclusion</h4>Tα1 promotes functional activation of CD8⁺ T-cells and mitigates exhaustion marker expression following chronic stimulation. These findings suggest that Tα1 could potentially serve as a supportive agent in T-cell-based immunotherapies by enhancing activation and partially reversing exhaustion in vitro, warranting further in vivo validation.

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