{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T19:54:33Z","timestamp":1791316473285,"version":"4.3.1"},"reference-count":20,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2023,9,14]],"date-time":"2023-09-14T00:00:00Z","timestamp":1694649600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Aging"],"abstract":"<jats:p><jats:bold>Background:<\/jats:bold> The immune-inflammatory response is the basis of the pathophysiology of SARS-Cov-2 infection. In severe cases of COVID-19 uncontrolled systemic inflammatory response causes multiorgan dysfunction (MODS), as the most common immediate cause of death. Unfavorable outcome of the COVID-19 most often occurs in elderly patients. The aim of the study was to establish parameters with prognostic significance in severe cases of COVID-19 according to life years, laboratory markers of sepsis and MODS, as well as the number of peripheral CD4<jats:sup>+<\/jats:sup> and CD8<jats:sup>+<\/jats:sup>T lymphocytes in 20 consecutively selected critically ill patients.<\/jats:p><jats:p><jats:bold>Results:<\/jats:bold> Eleven subjects were male, 9 female, mean age 73.45 \u00b1 11.59, among which the oldest patient was 94 and the youngest 43\u00a0years. All the patients met the sepsis and MODS criteria. Increased age and low CD4<jats:sup>+<\/jats:sup> and CD8<jats:sup>+<\/jats:sup>T cell counts were identified as independent predictors of death. Only the two youngest patients (43 and 50\u00a0years old) survived 28\u00a0days, and they are the only ones with a CD4 lymphocyte count above 500 cells\/mm<jats:sup>3<\/jats:sup>.<\/jats:p><jats:p><jats:bold>Conclusion:<\/jats:bold> Senescence of the immune system is mostly characterized by reduced regenerative capacity of adaptive immunity with diminished ability to respond to new antigens and a manifested proinflammatory phenotype. Additional reduction of protective capacity by further deterioration of T cell quantity and quality due to sepsis itself and mutual interaction of senescent T cells and vascular endothelial cells in the induction of cytokine storm represent two complementary vicious cycles in the development of sepsis-related multiorgan dysfunction.<\/jats:p>","DOI":"10.3389\/fragi.2023.1260053","type":"journal-article","created":{"date-parts":[[2023,9,14]],"date-time":"2023-09-14T16:12:19Z","timestamp":1694707939000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["Two vicious circles associated with the aging of the immune system in the development of severe forms of COVID-19"],"prefix":"10.3389","volume":"4","author":[{"given":"Miodrag","family":"Vrbic","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana","family":"Milinkovic","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2023,9,14]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"2247","DOI":"10.3389\/fimmu.2019.02247","article-title":"Immunosenescence and its hallmarks: how to oppose aging strategically? 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