Thymalin is a polypeptide complex isolated from the thymus and regulating the functions of the immune system. Thymalin is effective in therapy of acute respiratory syndrome, chronic obstructive bronchitis, and other immunopathology. Thymalin increases functional activity of T lymphocytes, but the targeted molecular mechanism of its biological activity requires further study. We studied the influence of thymalin on differentiation of human hematopoietic stem cells (HSC) and expression of CD28 molecule involved in the implementation of antiviral immunity in COVID-19 infection. It was found that thymalin reduced the expression of CD44 (stem cell marker) and CD117 (molecule of the intermediate stage of HSC differentiation) by 2-3 times and increased the expression of CD28 (marker of mature T lymphocytes) by 6.8 times. This indirectly indicates that thymalin stimulated differentiation of CD117+ cells into mature CD28+T lymphocytes. It is known that in patients with severe COVID-19, the number of CD28+, CD4+, CD8+T lymphocytes in the blood decreased, which attested to a pronounced suppression of immunity. It is possible that the antiviral effect of thymalin consists in compensatory stimulation of HSC differentiation into CD28+T lymphocytes at the stage of immunity suppression in unfavorable course of viral infection. Thymalin can be considered as an immunoprotective peptide drug for the prevention of COVID-19.

中文翻译：

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胸腺素：激活人类造血干细胞的分化

胸腺素是一种从胸腺中分离出来的多肽复合物，可调节免疫系统的功能。胸腺素可有效治疗急性呼吸综合征、慢性阻塞性支气管炎和其他免疫病理学。胸腺素增加T淋巴细胞的功能活性，但其生物学活性的靶向分子机制需要进一步研究。我们研究了胸腺素对人类造血干细胞 (HSC) 分化和在 COVID-19 感染中实施抗病毒免疫的 CD28 分子表达的影响。发现胸腺素降低CD44（干细胞标志物）和CD117（HSC分化中间阶段分子）的表达2-3倍，增加CD28（成熟T淋巴细胞标志物）的表达6.8倍。这间接表明胸腺素刺激 CD117+ 细胞分化为成熟的 CD28+T 淋巴细胞。众所周知，在重症 COVID-19 患者中，血液中 CD28+、CD4+、CD8+T 淋巴细胞的数量减少，这证明了免疫力的明显抑制。胸腺素的抗病毒作用可能在于在病毒感染的不利过程中，在免疫抑制阶段补偿性刺激 HSC 分化为 CD28+T 淋巴细胞。胸腺素可被视为预防 COVID-19 的免疫保护肽药物。胸腺素的抗病毒作用可能在于在病毒感染的不利过程中，在免疫抑制阶段补偿性刺激 HSC 分化为 CD28+T 淋巴细胞。胸腺素可被视为预防 COVID-19 的免疫保护肽药物。胸腺素的抗病毒作用可能在于在病毒感染的不利过程中，在免疫抑制阶段补偿性刺激 HSC 分化为 CD28+T 淋巴细胞。胸腺素可被视为预防 COVID-19 的免疫保护肽药物。