HK2 and COVID-19: Moreover, to validate the results from omics data, the mRNA levels of several genes shown in Fig. 2f in B cells were measured by RT-PCR, and we found that mRNA levels of HK2, SLC04A1, SDS, and COL1A1 were significantly decreased in B cells of COVID-19 patients compared to that of healthy controls (Supplemental Fig. 2).