{
  "abstract": "Acute coronavirus disease 2019 (COVID-19) causes marked T-cell lymphopenia, with recovery potentially driven by peripheral proliferation or increased thymic output of recent thymic emigrants (RTEs). We examined the relative contribution of these mechanisms by analyzing naïve T-cell and RTE dynamics in 63 patients sampled at 1-3 timepoints during and after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Overall frequencies of naïve CD4+ and CD8+ T cells remained stable during convalescence. In a female-biased subcohort with paired samples, CD31+ CD4+ and CD21+ CD8+ RTE-enriched subset frequencies increased from acute to late convalescence (LC) stage. Across the full cohort, a significant increase was confirmed for CD21+ CD8+ RTE-enriched subsets. PD-1 and Ki67 expression did not explain this rise, indicating enhancement of thymic output despite the cohort's high median age. Patients requiring ICU care had lower CD31+ CD4+ RTE-enriched subset frequencies in LC compared with non-ICU cases. Regression coefficient modeling identified male sex as a negative predictor of CD31+ CD4+ RTE-enriched subset frequency, potentially contributing to distinct CD31+ CD4+ and CD21+ CD8+ RTE-enriched subset kinetics. Together, these findings suggest that de novo thymic output, particularly CD21+ CD8+ RTE-enriched subset, contributes to T-cell reconstitution after COVID-19 and may influence susceptibility to post-infectious immune dysregulation.",
  "abstract_shown": true,
  "affiliations": [
    "Translational Immunology Research Program, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.",
    "Department of Bacteriology and Immunology, University of Helsinki, Helsinki, Finland.",
    "Human Microbiome Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.",
    "Division of Intensive Care Medicine, Department of Anaesthesiology and Intensive Care, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.",
    "Faculty of Medicine and Health Technology, Tampere University Hospital, Wellbeing Services County of Pirkanmaa and Tampere University, Tampere, Finland.",
    "Department of Virology, Medicum, Viral Zoonoses Research Unit, University of Helsinki, Helsinki, Finland.",
    "HUSLAB Clinical Microbiology, Division of Virology and Immunology, HUS Diagnostic Center, Helsinki, Finland.",
    "Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.",
    "New Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.",
    "Department of Pulmonology, University of Helsinki and Helsinki University Hospital, Meilahti Hospital, Helsinki, Finland.",
    "Helsinki Institute of Life Sciences, HiLIFE, University of Helsinki, Helsinki, Finland."
  ],
  "article_type": "brief report",
  "arxiv": null,
  "author_total": 14,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Xiaobo Huang",
      "orcid": "0000-0001-7516-8842"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Suvi T Jokiranta"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Kirsten Nowlan",
      "orcid": "0000-0002-8713-4823"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Ngoc Anh Nguyen"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Nelli Heikkilä",
      "orcid": "0000-0002-8879-1569"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Lauriina Tola"
    },
    {
      "affs": [
        2
      ],
      "name": "Anu Kantele"
    },
    {
      "affs": [
        1,
        3
      ],
      "name": "Pirkka T Pekkarinen",
      "orcid": "0000-0002-8203-3409"
    },
    {
      "affs": [
        4
      ],
      "name": "Johanna Hästbacka",
      "orcid": "0000-0002-3613-7231"
    },
    {
      "affs": [
        5,
        6,
        7
      ],
      "name": "Olli Vapalahti"
    },
    {
      "affs": [
        8
      ],
      "name": "Santtu Heinonen",
      "orcid": "0000-0002-1666-1933"
    },
    {
      "affs": [
        9
      ],
      "name": "Juuso Paajanen"
    },
    {
      "affs": [
        5
      ],
      "name": "Tomas Strandin",
      "orcid": "0000-0002-2454-7479"
    },
    {
      "affs": [
        0,
        1,
        6,
        10
      ],
      "name": "Eliisa Kekäläinen",
      "orcid": "0000-0001-6045-108X"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/41j6aa57r0fdt.bib",
  "cited_by": 0,
  "doi": "10.1002/eji.70303",
  "fulltext_url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13718309/?tool=EBI",
  "id": "41j6aa57r0fdt",
  "issns": [
    "0014-2980",
    "1521-4141"
  ],
  "landing_url": "https://europepmc.org/article/PMC/PMC13718309",
  "language": "eng",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "heading",
      "Clinical"
    ],
    [
      "heading",
      "Immunity to Infection"
    ],
    [
      "heading",
      "Short Communication"
    ],
    [
      "openalex",
      "2403|T-cell and B-cell Immunology"
    ]
  ],
  "openalex": "W7224342101",
  "pdf_url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13718309/pdf/?tool=EBI",
  "pmcid": "PMC13718309",
  "pmid": "42954665",
  "published": "2026-10-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/41j6aa57r0fdt.ris",
  "sources": [
    {
      "first_seen": "2026-10-31T00:20:39Z",
      "native_id": "PMC:PMC13718309",
      "source": "europepmc",
      "url": "https://europepmc.org/article/PMC/PMC13718309"
    },
    {
      "first_seen": "2026-11-01T00:20:44Z",
      "native_id": "MED:42954665",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42954665"
    },
    {
      "first_seen": "2026-11-02T12:22:21Z",
      "native_id": "PMC13718309",
      "source": "pmc",
      "url": "https://doi.org/10.1002/eji.70303"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "openalex:2403|T-cell and B-cell Immunology",
      "subfield": "immunology"
    }
  ],
  "title": "Increased Output of Recent Thymic Emigrants Contributes to Reconstitution of T‐Cell Pool During Recovery From COVID‐19",
  "title_text": "Increased Output of Recent Thymic Emigrants Contributes to Reconstitution of T‐Cell Pool During Recovery From COVID‐19",
  "type": "peer-reviewed",
  "updated_at": "2026-11-02T12:22:21Z",
  "url": "https://research.draconitic.com/paper/41j6aa57r0fdt",
  "venue": "European journal of immunology",
  "versions": []
}