CD4 and COVID-19: Considering that individuals with no COVID-19 history and those with COVID-19 both have SARS-CoV-2–specific memory T cells that cross-react with common cold coronaviruses, Coulon et al. investigated the phenotype of cross-reactive SARS-CoV-2–specific CD4+ and CD8+ T cells targeting conserved epitopes shared with other common cold coronaviruses.