Using markers for neutrophils as well as naïve and memory B cells and the markers described above for CD3+, CD4+, CD8+ T cells, Treg, CD19+ B, and CD56+ NK cells, whole blood samples from COVID-19 patients (time point 1; Bochum with n = 75 and Valencia with n = 22) were epigenetically quantified and compared to samples from the healthy subjects (Figure 2, Supplementary Table 6). Here, CD19 is linked to COVID-19.