Both C3d and properdin positivity in the tubulointerstitial area were significantly higher in COVID-19 than in bacterial sepsis (P = 0.034 and P = 0.001, respectively) and in the control group (P = 0.034 and P < 0.001, respectively) and were predominantly found in the peritubular capillaries. This evidence concerns the gene CFP and bacterial infectious disease with sepsis.