Furthermore, a study by Pontelli et al. found that live virus was found mainly in CD14+ monocytes and CD19+ B cells (both subsets were capable for endocytosis and could present internalized antigens on MHC II molecules to Th cells) upon in vitro infection of PBMCs with SARS-CoV-2, whereas infection of CD4+ T lymphocytes occurred less frequently [28], suggesting that the stimulation protocol used in our study is relevant for identification of virus-specific Th subsets in circulation. Here, CD4 is linked to infection.