We found an increase in both RBP4 and TTR in the serum of COVID-19 patients (Table 2), consistent with the secretion of this complex into circulation [54]; apolipoprotein C-IV (APOC4), a lipid-binding protein critical for activating lipoprotein lipase [57]; and immunoglobulin kappa constant (IGKC), an immunoglobulin isotype involved in immune response pathways such as the Fc epsilon RI pathway and NFAT in immune response. Here, IGKC is linked to COVID-19.