Thymic Function in Patients With COVID-19

The main clinical manifestation associated with SARS-CoV-2 infection is an influenza-like illness that follows the infection of the respiratory tract. In a few percent of infected people, inflammation of the lungs leads to severe pneumonia that requires hospitalization, in intensive care units for the more severe cases. Despite intensive care, a fatal outcome occurs in 6% and 12% of women and men over 80 years of age hospitalized for severe COVID, respectively. Factors associated with a higher risk of death in patients with SARS-CoV-2 include age and low circulating lymphocyte counts. Significant lymphopenia is indeed frequently observed in patients with severe COVID-19 and both phenotypic and functional changes in antiviral T cells have been correlated with the severity of COVID-19. The thymus, the organ that produces T lymphocytes, undergoes progressive physiological involution with age. However, in the elderly, rare cases of thymic hyperplasia are reported in autoimmune diseases or cancers, or are observed in response to deep lymphopenia, whether or not associated with sepsis. This cohort of patients treated for a SARS-CoV-2 infection could allow to better understand the role of the thymus in this pathology.