KLF6 and COVID-19: Finally, higher levels of KLF6, a transcription factor induced by TGF-β in DCs (29), was increased in pDCs in BAL from severe COVID-19 patients, while the MHC class II molecule HLA-DQA2 displayed lower transcript levels (Fig. 3I), in line with lower protein levels of HLA-DR detected on circulating pDCs.