CD4 and COVID-19: Moreover, a single-cell transcriptomic analysis of viral antigen-reactive CD4+ T cells from 40 COVID-19 patients got the conclusion that SARS-CoV-2-reactive Tregs were dramatically reduced in hospitalized COVID-19 patients, while the proportions of cytotoxic follicular helper cells and cytotoxic T helper cells responding to SARS-CoV-2 were increased (80).