PADI4 and COVID-19: In whole blood study, seven autoantigens were upregulated in blood of severe COVID-19 patients (MPO, PRTN3, PADI4, IFIH1, TRIM21, PTPRN2, and TSHR) (Figure 1B), while four autoantigens (MPO, PRTN3, IFIH1, and PADI4) were increased in blood of mild patients (Figure 1C).