T Cell Phenotyping in Individuals Hospitalized with COVID-19.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has become pandemic. Cytokine release syndrome occurring in a minority of SARS-CoV-2 infections is associated with severe disease and high mortality. We profiled the composition, activation, and proliferation of T cells in 20 patients with severe or critical COVID-19 and 40 matched healthy controls by flow cytometry.