CD27 and COVID-19: Antibodies produced by B cells are considered to be effective against SARS-CoV-2 because convalescent serum samples have been applied with supposedly good clinical results in COVID-19 cases 48 and were also previously used successfully in the treatment of SARS.52 We found that COVID-19 patients all have a group of plasmablasts in their peripheral blood, as characterized by a high level of CD27, IgM, IgG, and IgA transcripts.