T Cell Senescence by Extensive Phenotyping: An Emerging Feature of COVID-19 Severity

OBJECTIVE: To identify the potential prognostic value of lymphocyte subsets in COVID-19 patients, where lymphopenia is a common finding. METHODS: In 353 COVID-19 inpatients and 40 controls T cell subsets with markers of senescence and exhaustion were studied by flow cytometry. RESULTS: In severe illness, total lymphocytes B, NK, and all T subsets were dampened. Senescent CD4+, but mainly CD8+ T cells, increased in patients with respect to controls. The most significant index predicting fatal outcome was neutrophils/CD3+ T ratio. CONCLUSION: In conclusion, an altered T cell pattern underlies COVID-19 severity and is involved in predicting the outcome.